1982 300TD R134a conversion with parallel flow condensor update!! - Page 2 - PeachParts Mercedes-Benz Forum

dmorrison · #16 07-23-2004, 11:26 AM

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.

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,

, 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.

#17 07-23-2004, 11:32 AM

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,

R Leo · #18 07-23-2004, 12:02 PM

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.

#19 07-23-2004, 02:42 PM

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,

R Leo · #20 07-23-2004, 03:26 PM

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.

MT_Merc · #21 07-23-2004, 04:00 PM

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.

Rick Miley · #22 07-23-2004, 04:30 PM

Quote:

Originally posted by MT_Merc
... even if it's only 5 degrees outside.

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

R Leo · #23 07-23-2004, 04:48 PM

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

#24 07-23-2004, 04:59 PM

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,

R Leo · #25 07-23-2004, 06:54 PM

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!

dmorrison · #26 07-23-2004, 08:12 PM

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

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

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

oldnavy · #27 07-23-2004, 08:51 PM

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.

WannaWagon · #28 07-27-2004, 06:50 PM

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!

oldnavy · #29 07-27-2004, 07:08 PM

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.

oldnavy · #30 07-28-2004, 12:50 PM

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.