1982 300TD R134a conversion with parallel flow condensor update!!
 

Want to keep everyone updated on the R134a conversion I did in my 1982 300TD. This update is provided by the 100 degree day we experienced here in the DFW area:D :D

This was the "conversion" which consisted of a complete rebuild of the AC system. All new components-- Compressor, evaporator, hoses, orings, expansion valve, paralell flow condensor, R134a and synthetic oil ( good for R12 and R134a)

The posts.

The plan and comments.

http://www.peachparts.com/shopforum/tech-help/66621-review-my-plans-ac-system-comments-welcome.html?highlight=parallel+flow+condensor

Parallel flow condensor

http://www.peachparts.com/shopforum/tech-help/81979-parallel-flow-condensor-installed-w123.html?highlight=parallel+flow+condensor

Synthetic oil and why I used it. Because the system can now go between R12 or R134a WITHOUT FLUSHING.

http://www.peachparts.com/shopforum/diesel-discussion/80208-ac-system-rebuild-synthetic-oil-r12-r134a.html?highlight=parallel+flow+condensor

The new compressor vs. old
Some techs I trust said to never use a rebuilt R4 compressor. 90% of the time they fail after 1-2 years.

Installing the dash
Remember I had a leaking evaporator which started all of this.
Notice the amount of crud blocking the evaporator in the pisture about half way down. This may have a significant effect on your conversion.

http://www.peachparts.com/shopforum/diesel-discussion/80341-order-installing-evap-box-w123.html?highlight=dash+dave

Compressor seals and hoses.

http://www.peachparts.com/shopforum/tech-help/82396-ac-rebuild-one-step-forward-two-steps-back.html?highlight=dash+dave

Sooooo hows is it going. The other day it reached 100 Degrees here in the DFW area and I will tell you that the car is very comfortable. I posted that I would like to compare it to a 123 R12 system, but Larry Bibles is not working. I got my daughters 240D system working. Its R12. was low on R12 and after adding a can I could not find a leak with my sniffer anywhere in the system. I spent 2 hours searching and no leak. I have added dye with the last can added to bring the pressures up to normal operating limits and so far no dye in the evaporator drip :D :D

So to compare the 2 lets discuss the differences. The 240D has no tinting. I run R12 in a standard system with pressures of 22 low and 265 high. The 82 300TD has R134a. A NEW evaporator as well as everything else. tinting, legal tinting, and a parallel flow condensor. R134a and the aux fan is on all the time. I'll try the system with it in the normal mode.
I think the 240D r12 system cools just a little better, may 5% better. My temperature guage for the vents, I think is wrong. But by driving both cars I think the rebuild to R134a is a success.

BUT here are the caviots.(sp)

I have a NEW evaporator, The blockage of the old one was significant. What is the blockage on the 240D, I do not know. Air movement is good, as good as the 300TD? It seem so. What is your cars evaporator like, That may be a consideration. I wish there was a way of checking them without a boroscope or taking out the dash.

So the conclusion, Go with a parallel flow condensor if you are thinking of a R134a conversion. I will get a new thermometer and post the 240D and 300TD temps.
Use synthetic oil after the flush. If you are not happy with the R134a then converting back to R12 only requires an evacuation and recahrge. No flushing.

I hope we can get someone to post who has done the conversion WITHOUT the parallel flow condensor.

Yes I am very happy with the vent temps, Idle speed temps and the results I have gotten. All comparing it to the 240D With R12.

Dave
7709

Let the posting begin.

Fantastic post subject
 

Hmmm.
It would not shock me to find automotive climate control engineers following this thread.
This is a great subject with tons of food for thought.

Dave, You are one ORGANIZED man. Great info......

Dave,
What a great thread! It's good to see all the speculation and guessing about what to do to improve the a/c systems on these cars finally turned into action and fact. Now I know what I'll be doing this winter.

Take care!



:D

Dave, do you plan to convert the 300 to R12 once you're sure it is leak free? That would provide another very interesting data point.

That's the way pilots are.

Dave,
The other thing that you may have overlooked on your post is that the TD's interior space (wagon vs sedan) is larger than the 240. Therefore more work. AND the 134a conversion is still working pretty close to the 240's. Good job.

Your next project should be to find a used boroscope on Ebay, design an attached water jet AND then we can rent it from you to clean our evaporators.

Eric

Dave -

Interesting timing on your post. I just changed my 124 diesel wagon from R-134a to R-12 last night.

I went through about the same process as did you. Everything got replaced - evaporator, compressor, condenser - everything. I got lazy and used a stock condenser instead of fitting a parallel flow. Perhaps as significant as all the other repairs, I replaced all the vacuum actuators. The car no longer wastes any cold air out the defroster vents, and 100% reciculate mode is definately 100% recirculate mode. Stinky cars up ahead no longer fumigate the interior of this 124.

Like you, I used a universal synthetic refrigerant oil that operates with both R-12 and R-134a. I elected to initially charge with 134 because it was so much cheaper - better to lose a $10 charge if had a problem.

Surprisingly, the 134a worked pretty well in the 124. This is a combination everybody says doesn't work, but I found it OK. It worked great all spring and into the early summer. It was adequate even on our 100 degree days. If the car had been sitting in the sun, it took about 10 minutes of stop-and-go driving to become fully comfortable inside.

I used an a/c thermometer to measure the temperature of the air discharged by the system. On the highway after dark it would put out 39 degree air, after the blower had slowed . During the day, with the fan speed up reasonably high, it would deliver 50 degree air in stop and go driving. Sitting at long traffic lights in 100 degree ambient temperatures it would creep up to 60 degrees. Accelerating away from the light it would rapidly cool down.

Now that may not sound so great, but surprisingly it kept the car comfortable. I think a lot had to do with fixing the recirculate function. When the car is not drawing in hot, humid air, the system does a better job of dehumidifying the interior of the car. Removing moisture from the air is a big part of why air conditioning makes us more comfortable. I guess very dry 50 degree air will actually do the job on a hot day.

System pressures with the 134a were OK. I charged until the low side came up to ~25PSI with the engine at 2000RPM. High side settled in at ~325PSI under those conditions - a touch higher than I like. But that's in my garage without good airflow over the condenser.

I don't have any performance figures for the R-12 yet, but will follow up when I have some data.

How come you think your temperature numbers are fouled up?

- JimY, fellow a/c hacker

" Accelerating away from the light it would rapidly cool down. "
Sounds like a high performance Aux fan might help out...and it is ealy to install ....We are not into AUGUST yet.... LOL

Well let me answer all the questions and comments by "poster"

leathermang

"You are one ORGANIZED man."

With my flying yes, My garage, PLEASE don't look at it. It really is a mess. When the kids go back to college, the garage is a major reorganize project.

Rick Miley

I originally was going to put the R12 into the system once the "mods" proved reliable. But now I don't think I will. The setup has proven to be a good system and I don't think going to R12 would gain me any advantage but a $120 bill for freon. So for now it will remain a R134a system.
Now if Larry Bible wanted to lend me some R12 for a couple of hours we could run a test. Take vent temp readings. Remove the R134a and install R12 then take the same readings. Then remove the R12 and install the R134a, unless the R12 readings were much more impresive.

Eric Eliel

Yes the TD is bigger. But is it balanced due to the tinting? I don't know. But it is a factor.
Harbor Freight does have a boroscope for $169 on sale at times, a non flexable unit. Getting to the evaporator would be an absolute PITA. You would have to go thru the fan opening and get to the evaporator. I don't know if it is possible.

Its now Wednesday night, 6 hours after I started this post

I did get a new thermometer (old guage read 9 degrees higher than the new one in the vent side by side) and drove the car tonight. The first 10 minutes was hot, car was sitting in the sun. The temp would only drop to 40 driving around town. 38 on the highway. So maybe I will consider the R12. Tomorrow I will do the same with the 240D that has the R12. See how the stop and go temp readings are and then decide about the R12.

Jim

Consider hot wireing your fan so its on all the time. I disconnected the temp switch in the reciever/dryer and made a jumper for it. So the fan is on anytime the car ignition is turned on. This was I get the fan cooling the parallel flow condensor at all times.

Dave

parallel flow condensor
 

whats the diff between a parallel flow condensor and a standerd condensor

Dave,
I think it would be great if you can stay with the R134a.... Comfortably.....

Of the things you have changed out....the P condensor may have only offset the reduced efficiency of the R134a...

So, since we know that ' airflow across the condensor' is the primary limiting factor in ANY AC system....

Why don't you put one of the high performance Aux fans on your system before you make the decision on switching back to R12 ?
See if that makes the difference on keeping you cool with the R135a ?

leathermang

fan is hotwired so it on whenever the car is on. A high flow may improve the situation.

But here a twist to the story.

Took the 240D today. New thermometer, same one use to post the temps above.
The car vents temps ran at 42 down the highway, 40 at one point, Vs. the 40 and 38. Outside temp is about what it was yesterday driving the 300TD.

Starting the car, then ran down the road, it acted like the 300TD. Very hot until just outside the neighborhood. Cooled down nicely but as I said 42 degrees in the vents.
I will put the guages on the car, check for leaks with the sniffer and the dye light. See if the R12 is leaking which may explain the higher temp in the R12 system vs. the R134a system.

I'll post when I get it done.

Dave

Tangent, sorry

Go here to learn the difference. Basically the same size parallel flow condensor is 30-35 % for efficent so the removal of heat from the freon is better, which with a converted R12 to R134a system you need.

http://www.ackits.com/index.cfm?fuseaction=Parallel

cool
 

thank you
i love to know how thinks work

GREAT THREAD! And Great job on the a/c refurbs!

As I was reading through I was thinking that I needed to post and ask for vent temps and you got there.

I have never had any doubts that with enough condensor capacity that 134 would cool a 123 with no trouble. The 124 would be tougher, but can be accomplished as Jim Yuhn has shown with his project.

A big part of the evaluation is objective. And that is, different people require different levels of "cool." That's why I like to see vent temps, that takes out the objectivity.

It is guys like Dave Morrison and Jim Yuhn that take things forward. Their inquisitive and scientific nature is the necessary ingredient in finding methods of improvement. These guys have sort of a Smokey Yunich approach toward air conditioning.

BTW, I don't have non working a/c's in my 123 cars, I have non working 123 cars. If they ran, I think the a/c's would work okay. Maybe some day, I'll put the 240D back on the road.

I have done 134 conversions in the past, but I have never done a CORRECT 134 conversion. By this I do not mean that I don't flush, r/d, correct oil, evac, etc. I mean that I have never improved condensor capacity to do the conversion correctly.

I really have no problem with 134 conversion if it can get the job done. What I DO have problems with is using snake oil refrigerants.

Good job guys,
PS. Dave did you ever get the modulator working correctly on your daughters transmission? LB

OK, first view of the R-12 performance in my 124. I've only driven it one day, so this isn't based on a lot of data. Thursday was a sunny and modestly warm day by Dallas standards, with a high temperature of 95 degrees.

The R-12 performed better during the morning commute, generating vent temperatures in the low 40s during my suburban stop-and-go commute. In comparison, R-134 would only drop to the upper 40s under the same conditions.

I ran some errands at lunch, when the temp was well into the 90s. Vent temperatures were perhaps 2-3 degrees lower than R-134 under the same conditions. I saw about 47 degrees with the blower running at a medium-high speed.

Heading home after work in mostly stopped traffic the vent temps were in the low-mid 50s - again, perhaps 2-3 degrees better than R-134.

When charging, the high side pressure was about 50PSI lower than R-134 under similar conditions.

Subjectively, the R-12 seems to cool down faster than the R-134. The air gets cold in less time. Though it does get a bit cooler, the difference isn't significant enough to notice without measurements. In both cases the car was comfortable at all times.

I don't think hard wiring the condenser fan will make any real difference. I have the newer red switch in place. The fan always comes on within a few seconds of bringing the car to a stop. It's pretty much running all the time that it will be useful.

I expect a parallel flow condenser would improve the performance of both R-12 and R-134 on the 124 chassis. However, another limiting factor is the compressor. The early 124 cars used a Nippondenso 10p15c compressor. Now, this is a nice little compressor, but the accent is on little. It has a displacement of 145cc. In contrast, the R-4 commonly used on the 123 diesels has a displacement of 176cc. In my opinion this makes a 123 a better candidate for conversion than an early 124. There's a reason Benz later switched to the larger 10P17c compressor.

OK, 'nuff rambling for today,

- JimY

Love computers, finished a reply and the computer froze, so everything was lost.

Larry
I agree AC operation and "feel" is subjective. I prefer the vent blowing directly on me at full cold while driving here in the Texas summers, to the point that my glasses always fog up when I get out of the car. My wife prefers NOT to allow it to blown on her, unless its very hot. She will always turn the fan down when she is comfortable instead of going to auto and allowing the AC control unit to regulate. I have tried to teach her, but her heart is really in the 240D mode, everything manual and you decide what you want, not some machine.
I also prefer the tinting in the car. My daughter hates it. So when driving the 240D I really feel the sun "beating " down on me. Maybe I'm aware of it due to the MD80 aircraft. Our side windows are plastic, thick but platic. They allow UV rays to go thru them, So we are aware of the UV factor which I feel as the sun"beating" down on us. The front windows are glass and do not allow the UV rays to go thru them. Crews of the MD80
have to be aware of skin cancer due to this.

Back to cars. So I like tinting Maybe this is why I'm happpy with the 300TD's Ac performance.

I would like to research installing a larger capacity reciever/dryer and/or 2 units in series or parallel. This might prevent the vent temp rise that occurs in stop and go and stoplight situations. Is the rise in vent temps due to the small reserve of chilled liquid freon in the r/d or is it due to the compressor output at lower RPMs? Anyone know?

Larry the 240D tranny is working fine. Replaced the 2 air switches on the valve cover, even only 1 is tranny related, and the injection pump vacuum control unit ($165.00 ouch!). The "old car" guy at the dealer advised replacing the IP vacuum control unit to 1 fix the problem and if that does not fix it. Then 2, you really need to replace it if your installing a new/rebuilt tranny. A bad control vlve can ruin a new/rebuilt tranny in a couple of months.
So it was replaced and the car is running fine.

jcyuhn

Out vent temps were taken on the same day for your car and my 240D. The 300TD temps were taken the day before. Both days were about the same temp/humdity wise. So were getting a data base here. One difference is that your in the Dallas side of the metroplex and it does tend to be a "hotter" area of the metroplex due to more concrete over in the Dallas area. At least were sort of comparing apple to apples, Well except your is a macintosh and I have a granny smith and a red delicious. At least we're not comparing apple to oranges. OK stupid comparison. :D

The R12 system will cool down faster that the R134 system. R12 is more efficent at heat exchanging then R134. That is why the R134a system is built "with larger capacity". so apple to apple the R12 vs. R134a the heat in the condensor is not eliminated as quickly. That is why the high pressure switch must be installed in a R134a conversion.

"OK, 'nuff rambling for today,"

This is not rambling, this is important, :D , Open discussion, thats rambling

Dave

PS could someone else post some vent temps that lives in a hot area. Were trying to get some bassis here, but were talking about systems that have been "messed" with and our messing may have thrown to many variables into the equation. Vent temps from a non"messed"with system would be helpful.

Great data Jim. You bring up a good point about the compressor.

I remember years ago hearing refrigeration engineer say that it doesn't matter how much compressor you have, "if you don't have enough condensor, you won't have enough capacity," or something to that effect.

That said, if you don't have enough compressor, you will still have a problem. You may have really hit on the reason that the 123 seems to convert with a little more success. It also indicates that using the late 124 condensor and fan may not be enough mod without using the larger compressor to go with it.

Thanks for the data and the persistence in gathering a/c knowledge and experience and sharing it with us. The same thanks to Dave.

Have a great day,

134a data points
 

134a system, OEM condenser, 300TD, orient red (maroon), tinted glass. Evaporator cleaned as much as you can reach with a long brush through the fan motor hole (last 2-3" still dirty and no telling what is actually IN the coils).

Today's data:
56-58° F outlet temp, 76° F outside temp.
Moderate stop and go traffic during morning rush hour commute.

62-65° F outlet temp, 98° F outside temp
30 minute commute home in stop and go traffic with one short sprint on the highway.

Observations:
— at the very least, the 134a system in this car needs a PF condenser if not a full blown R12 retrofit.
— Ambients over 95° mean long cool-down times and overall ineffective cooling
— conversely, nightime driving in 65-75° ambients waill cause you to select the low blower setting
— The cargo area never really gets all that cool.
— On a hot day, I can detect a difference in outlet temp (decrease) if I happen to stop in the shade at a traffic light.
— A/C puts a heavy load on the engine too...noticble decrease in power at times.

Thanks to both Dave and Larry for sharing your time and expertise on this project.

R Leo,

You know that performance just doesn't sound like a 134 conversion. I wonder if there is something else going on to make the car have vent temps that high. If you had trouble with the monovalve or a temp sensor it might be part of the performance problem.

Dave is pretty darn savvy now with the 123 climate control, he might have some other ideas.

Good luck,

I thought the performance seemed weak too. In the past, I've pinched off the return hot water hose thinking I had a leaking monovalve problem but didn't notice much if any difference.

I suspect that the evaporator is plugged pretty badly and my compressor is making some noise if the head pressures go up (long idle, etc) so it's probably dying too.

Consider hot wireing your fan so its on all the time.

A better choice would be to hot-wire it to the climate control side of the pressure switch. That way the fan comes on whenever the air is on rather than being on whenever the car is running, even if it's only 5 degrees outside.

Most of the guys talking here are in Texas. Hence the obsession with Air Conditioning.

If it's 5° outside, I'm not too worried about the operation of my air conditioner.

Well, I guess I'll have to go put one of the 123's on the road so I can add some data to the pool.

Dave, I think you cleared something up in my mind. The condensor is the most important component as far as determining a/c capacity, but in a car, it stands to reason that more compressor capacity will allow you to have more capacity at lower RPM, thus a little better at idle and slow traffic.

I don't know if that theory holds water, but it sounds good.

I'm glad you got the transmission straightened out. Yes that doodad on the back of the IP is ridiculously expensive.

Have a great day,

134a Update
 

Larry, thanks for the reality check. When you said the temps didn't seem right I got to thinking that the refrigerant charge might be all wrong. I've never been in the system on this car and I don't own a gin-yoo-wine set of 134a gauges either so I stopped at the parts hut on the way home and bought a cheapo $10 gauge that you can stick on those beer can sized refrigerant bottles of 134a. I plugged it onto the suction line and at idle the low side was running damned near in the red.

The PO (or someone) had OVERCHARGED the system. No wonder I couldn't get any decent cabin temps.

I carefully bled the system down to where it says 'filled' on the gauge and at idle (+95° ambient) I'm getting about 58° F. A short cruise down the street brought the temp down to 54° fairly quickly. Prior to this, I'd barely get 68° at idle. I'm encouraged.

I know this tool isn't the 'right' way to do this job but desperate times call for desperate measures; I'm looking at a 200+ mile trip tomorrow with SWMBO and all the dogs in the car. I need to keep the whining to a minimum.

With a PF condenser and a good cleaning of the evap, there may be hope for this 'ol 134a system after all.

Thanks all!

CRAP!!!!!!!!!!!!!!!!!!!!!!!!!!

Well I can't believe it but my daughters evaporator is leaking.
:mad: :mad: :mad: :mad:

I felt the R12 system should have been running a little better than what we were getting so I really attacked the system with the sniffer.
Found some dye around the expansion valve, inside the foam cover, and removed all the tar like sealant from the expansion valve and the tubes of the evaporator going into the housing. Placed the sniffer around the expansion valve hoping it was the joints. Not very many beeps form the sniffer. Dug out the tar sealant going into the housing and everytime I placed the sniffer at the rubber gromett gap she went off.

CRAP!!!!!!!!!!!!!!!!!!!!!!!!

Have to replace the evaporator. Been there, done that and I don't want to to it again.

I've called Phil about the evaporator, and I'm afraid a couple of other shops. They all call for either a 123 830 22 58 housing or a 123 830 32 58 or 40 58 housing for the 240D. My housing is 123 830 30 58.
So I need to confirm with them that ther unit will fit before I take everything apart and find out I'm waiting for a part because I got the wrong one.
Or worse I can't get it aftermarket and have to shell out the $907.00 at the dealer for a new one.

Before doing that I would look at welding the current one.

I hate finding out about things like this on a Friday afternoon after everything is closed.
Do I start disassembling things or wait?

I have to figure out wether I convert and to what degree or remain R12. I'll have to have the R12 recovered, don't have a machine. $100 gone.
Called ACKITS.COM to figure out if the R4compressor is OK for R134a. they advised there is no way to tell unless you have a date stamped on the compressor, I can't find one. So the R134a would be more expensive. New compressor $226, R134a $12, parallelflow condensor $81.40, R/D ( already have), manifold $25, evaporator $250, expansion valve $26 = $620.00 or
Evaporator $250, freon $120, R/D (already have), No compressor, no expansion valve. system has and is running fine except for the leak=$370

Since my daughter has to pay for it I think I'll save her some money and stick with the R12 setup.

So everyone how's your weekend starting out??

Dave

My 134 conversion works great when not in stop & go traffic, but will freeze you to death on the road. A friend said the thing I needed to do was replace my a/c pressure switch on the dryer, with the new updated switch that will cause the aux fan to come on sooner and compressor kick in earlier. I have it ordered from the dealer, I'll let you know if it helps the low speed a/c problem.

oldnavy:

Got a part number on that pressure switch? Sounds like something I could use, too. Have you installed it and tried it yet? How does it work?

Thanks!

I have it ordered, but can not find the part number here at home. I expect it to show up in the next couple of days, then I can give you the part number. I can probably get it tomorrow from the dealer for you, if you like.

Pressure Switch Part #
 

Old # on my 240D is 1248213651, new # is 000820810 and is listed as for R134 coolant. Dealer said list was $40+ and my cost $35 and no shipping charge. Dealership is in Springfield MO.

If you want to call and talk to MB parts (Larry) call 1-800-725-5800 and after the girl mumbles all the words togeather (sic) ask for MB parts. There is only one guy in MB parts, and that's Larry.

Oldnavy: thx for the part number. Do you happen to know if this switch can just be simply removed and reinstalled without discharging the AC system? I know this is possible on other cars. Does it work the same on ours?

P.S. -- I like the quote in your sig and agree heartily! ;)

WannaWagon..
no, the temp switch can be.... but the pressure switch will let the refrigerant out if you take it out...

I've been told the oppesite by 2 MB tech, and one indepentent. The indy said it will do a pop like taking off an air hose of a tire, that there is a valve in the mount just like where you connect your charge hose.

So who do you believe ? Those two MB techs or ME ?
Time to declare your loyalty one way or the other....

Hint: Do you think I would ask this if I could not post a picture of the Factory Shop Manual saying exactly what I said ?
Or maybe I am bluffing....
What are those MB techs names and contact information ?
We need to start procedures for taking away their license.... because opening up the AC system like that can be dangerous if you are thinking it is only going to " POP" and seal itself up....

---------------------------------------------
U.S. Army Aviation 1967-1971

Man you ain't giving nobody (me) any slack are you dude. :eek: ;)

I will say that I will check it out and see, but the indy is a personal friend and certified VW tech Oilhammer.com , I'll recheck with him before I do replace the unit.

Please let us know one way or the other. This simple question got heated!:rolleyes:

I am not heated....
I am just asking for a vote of confidance/no confidance...
I even offered a great hint.... and have said before that I very seldom say anything which is not directly from the Factory Shop Manual on Air Conditioning...
I will offer even another hint...
PAGE 83-532 Service Manual Heating , Air Conditining, Automatic Climate Control model 123
middle of the page under " note".....

NOW who do you trust ?

LOLOLOLOL

VW TECH ? Maybe VW does have this feature....
Old Navy, Wear goggles and gloves anytime you are dealing with AC stuff... all the manuals say this repeatedly.... for good reason...

Yes he's a VW tech, but he loves the MB's and has a 300D.

PS: I don't have Automatic Climate Control, thank God. I guess I'll fire up my CD and check for myself.

Leathermang I just ordered a new green dashpot valve today, it would pass air the same from both directions. :eek: Could you tell me what this check valve does?

Man, this is really an excellent place to hangout. :cool:

Maybe he owns a 300d... but not the MB Air Conditioning manual?

PS.. I have a 1980 240d with the MANUAL WIRE CONTROL AC... thank goodness for that also... but that is covered in this manual also...

You have the CD ? But were taking the two MB techs and your friend's word on this ? LOLOLOLOL .... On the other hand.... if you trusted the FIRST one you asked.. why did you ask the OTHER two ? LOLOLOL

"new green dashpot valve " I don't know many things without looking them up.... the only dashpot valves I remember were on Gasser carbs.... where does this thing plug into ?

PS ... is this what you have ... lookds like Jbaj007 answered it...
http://www.peachparts.com/shopforum/diesel-discussion/51501-please-identify-part.html?highlight=dashpot

Yup, that's the little green devil. What I was wondering, is how do you know which way it goes? It was $7.25 delivered, so it wasn't too bad.

As for as the a/c goes I'll take it to the local Dodge dealer and have it installed, because I was really thinking that it would do a sudden dump of my 134a. ;) I don't mess with anything that I don't have the equiptment to work on it in garage. I'd rather spend $67 for the part to be replaced, then screw something up and that includes my eyes or hands. If I don't have the proper safety equiptment for the job, I never do the job. By my grinder is the safety goggles and I always wear my safety glases in my shop intead of my street glasses.

It does not matter which way you install it..... the function is to dampen small changes in vacuum ... so they do not adversely affect the stuff the lines are attached to....it is sort of a resevoir and thus transmits changes less than a narrow line would.

So which end goes toward the IP, the end with Pierburg part # or the other? Should I be able to only blow through it in one direction?

Since it is not a valve... I do not think it makes any difference which end goes where.. unless the size only matches one direction....
Can you only blow through it one direction ?

I can blow through the old one in both directions. Don't know about new one as it hasn't arrived as yet. It is black inside and appears to be original as the production date is 2-1-82.

Since we are dealing with vacuum... can you suck through it both directions ?

Yes I can.

And I can tell no difference in operation of car if I switch it around.

What made you decide to replace it ?

well I figured it was some type of check valve and if it didn't restrict flow in some way it was bad. Otherwise why have it in the line.

A vacuum pump is an air pump but hooked up to the back end... it pulsates.... and you don't always want those pulses transmitted to the things being operated...so this is a ' dampner' by its very nature of being wider than the lines which run to and from it.... this is the same as an air tank on a regular air tank... your tools don't ' feel' each pulse of the pistons....