Orifice tube install... - Page 5 - PeachParts Mercedes-Benz Forum

1980sd · #61 08-29-2011, 02:09 PM

Lost in other threads but... I put a PF condenser, new fan, Sanden 7 cyl compressor, orifice tube and accumulator in place of the expansion valve along with cleaning the evaporator and troubleshooting the ACC system.

Anyway, after chasing a couple of leaks I had it charged with 2 lbs of r134a today. At about 2000 rpm the low side pressure was 30 psi and the high side pressure was 200 psi. Vent temps at idle were 45 degrees but it dropped down to 40 degrees on the road. This was with the outside temp about 95 degrees.

Not stupendous but it's almost EXACTLY what I had with the old R4/TXV setup. Weird huh?

Things I noticed:

The condenser was pretty hot at the outlet.

The accumulator got REALLY cold and began to "sweat".

There was a LOT of condensation coming from under the car.

I could feel the temperator difference between the inlet/outlet sides of the OT holder.

When the compressor was switched on I couldn't feel the engine bog down at all.

I went with an .062 orifice tube for the heck of it but there are lots of other sizes as well as a variable OT available.

http://autoacrepairs.com/Orificetubesize.htm

Some links to the project.

Anyone considered orifice tube conversion?

Orifice tube install...

Condenser size (AC condenser)

Compressor bracket... 1980 300SD

Evaporator cleaning, scope vid.

I plan on running it for a few weeks and then changing the OT and maybe tinkering with the charge. The guy at the shop said it would probably take a little more charge but I should run it and then check for leaks before topping it off.

I'm thinking a white GM OT should flow a little more and drop the high side pressures some.

Any input? I'm pretty happy with it. Not a meatlocker yet but I didn't go backwards with performance

Here's a video of some preliminary performance:

http://www.youtube.com/watch?v=KoBkf3xqH78

I think some twiddling can make it a little better.

Strange, the vent temps are lower on the low blower speeds... It could be because it picks up 20% outside air when on "high cool" ??

vstech · #62 08-29-2011, 10:14 PM

Generally, it's best to keep updates on the original thread, or at least include links to both threads in both threads...

1980sd · #63 08-29-2011, 10:36 PM

Quote:

Originally Posted by vstech

Generally, it's best to keep updates on the original thread, or at least include links to both threads in both threads...

Sorry, my documentation is like my execution, scattered, endless

Any input on the data? I'm thinking I need to put a wad of dum-dum on the fitting into the evaporator. Looks like it will sweat.

How about the pressures?

Another update in case anyone is following.

I let it sit overnight and fired it up for some more testing. It was 85 deg here and I got 39 deg vent temps at the center vent at speed. The instruments are still out because I'm paranoid about leaks

I took it by the shop that charged it and had them sniff behind the instruments and at the vent and all looked OK.

I got some grease tape for the lines inside the car because there was quite a bit of condensation and I noticed frost on the suction line.

I'm not using any CCOT switching other than the ETR switch which is supposed to shut down the compressor when the evaporator reaches 36 deg. I'm not sure if it has cycled yet.

I was considering running a light that will come on when the compressor is on so I can see what it's doing. Not sure how to do this yet

Can't really do a lot of road testing with the dash out because I have no gauges, charging etc.

I'm getting TONS of condensation from under the car and frost on the line leaving the evaporator so I think the charge must be OK.

More update:

Got the fittings behind the instruments insulated, put the dash in and went on a 30 mile ride. 89 deg. outside and I got 35 deg vent temps after some running. I let it run in the garage with the AC running for about 10 minutes and the vent temps rose to 40 deg....

1980sd · #64 04-30-2012, 07:14 PM

First day in the 90's

No complaints with the AC after driving over 100 miles. Vent temps in the low 40's, cold knuckles. It does seem to drink more gas though...

vstech · #65 04-30-2012, 07:17 PM

you should not have frost on the lines... charge may be a touch low. or the orifice may be a touch small...

1980sd · #66 04-30-2012, 07:46 PM

I'm running a .067 Ford blue OT now. I picked up a white GM tube (.072 I think...). I'm planning on changing the accumulator, drier and OT in the future just to see how much crud the filters picked up. I'm guessing the larger OT will bring the pressures down a bit.

I'm also planning an OT R4 project. The thought is that the OT won't "throttle" the refrigerant and oil like a TXV. This, along with an accumulator and larger return lines (10 vs 12), should also help keep it lubed.

Any input?

1980sd · #67 06-07-2012, 08:06 PM

I'm back at it...

It's finally getting hot again so I can go ahead with more testing. Plus I have some more AC tools which make experimenting easier...

Anyway, I had a leak where the hose leaves the receiver. Everything else was fine except that spot. I could see bubbles with a soap check and it stayed wet with PAG oil. I only put 2 cans of 134a in it over the winter just to keep it running so I had defrost, so it wasn't leaking that bad.

I figured it was just a bad crimp or something but when I took it apart I noticed this:

I somehow ended up with a barbed fitting instead of the bubble type (I think) that my crimper is made for. Just something to be aware of if anyone decides to get into this stuff.

This is the crimper:

It's a Masterkool 71550. Lots of info on them on the web. Pretty nice rig for the DIY'er. I even did an oil cooler line with it and it's been holding up for about 30,000 miles!

Soooo....

I removed the hose from the receiver to the orifice tube holder and and re-crimped a proper end in place. While I was at it I replaced the .067 Ford OT with a .072 GM tube. Just something to monkey around with. I read on the interwebs that the Ford blue tube was supposed to work better with 134a so that's why I used it initially. I gotta say that it did work well but other problems (Belt slippage, freon leakage, etc...) really kept me from getting a consistant baseline.

I also believe that I finally licked the belt slipping problem but miles will tell the tale...

Here's the old OT:

The screen was really clean. What looks like brass chips in the picture is actually just PAG oil. I was expecting to find some puddled in the hose because it's a low spot but it didn't have any in it. Just in the OT screen

Well, I got it back together and pulled a vacuum on it for an hour and let it sit for another hour to check for leaks. All looked good (Yea, I know, not the best way to do it but what the hey. If it quits working I'll suspect a leak

)

After slinging 24 Ozs of 134a in it I was getting Hi of 150 psi and lo of 30 psi at 85 degrees and the vent temps were low 40's.

A test drive of the AWESOMEMOBILE was so sweeeet it turned into 60 miles

Vent temps were high 30's and after a bit the ACC cycled the fan down and began tempering the air. This was mid 80's and cloudy so not the best Ga. heat test but it's promising!

Yea, that's ICE in my engine compartment... I'm guessing my charge is a bit low but it didn't seem like the evaporator was freezing

Plus the ETR never shut the compressor down. I'm pretty sure the ETR works because it seemed to cycle during the winter.

engatwork · #68 06-07-2012, 08:28 PM

Good job Jon

.

1980sd · #69 06-07-2012, 08:46 PM

Thanks Jim! What do you think about the accumulator icing up? It does seem to be working pretty darn well though...

engatwork · #70 06-07-2012, 08:57 PM

Sounds/looks like it is working pretty good to me. How bout a pic of what you came up with in regards to the belt tension.

Markp · #71 06-07-2012, 08:58 PM

Wow, nice AC system!

1980sd · #72 06-07-2012, 09:16 PM

Quote:

Originally Posted by engatwork

Sounds/looks like it is working pretty good to me. How bout a pic of what you came up with in regards to the belt tension.

It's the same system you engineered last summer

The tension bolts I was using were at the end of the travel and it was "almost" putting enough tension on it. With 116 balancer legends I was being conservative with belt tension! I just put some longer bolts on it and tightened the belt a little more.

Thanks Markp!

vstech · #73 06-08-2012, 01:56 PM

Quote:

Originally Posted by 1980sd

I'm back at it...

It's finally getting hot again so I can go ahead with more testing. Plus I have some more AC tools which make experimenting easier...

Anyway, I had a leak where the hose leaves the receiver. Everything else was fine except that spot. I could see bubbles with a soap check and it stayed wet with PAG oil. I only put 2 cans of 134a in it over the winter just to keep it running so I had defrost, so it wasn't leaking that bad.

This is the crimper:

It's a Masterkool 71550. Lots of info on them on the web. Pretty nice rig for the DIY'er. I even did an oil cooler line with it and it's been holding up for about 30,000 miles!

Soooo....

Well, I got it back together and pulled a vacuum on it for an hour and let it sit for another hour to check for leaks. All looked good (Yea, I know, not the best way to do it but what the hey. If it quits working I'll suspect a leak

)

After slinging 24 Ozs of 134a in it I was getting Hi of 150 psi and lo of 30 psi at 85 degrees and the vent temps were low 40's.

A test drive of the AWESOMEMOBILE was so sweeeet it turned into 60 miles

Vent temps were high 30's and after a bit the ACC cycled the fan down and began tempering the air. This was mid 80's and cloudy so not the best Ga. heat test but it's promising!

Yea, that's ICE in my engine compartment... I'm guessing my charge is a bit low but it didn't seem like the evaporator was freezing

Plus the ETR never shut the compressor down. I'm pretty sure the ETR works because it seemed to cycle during the winter.

ok,
when are you putting the crimp tool in the rental thread?
I WANT IT!!!

anyway, the ice is indeed indicative of low charge. 150 head is a sure sign! it also shows the condenser is working well. 24 oz sure does sound low, heck, you've got an accumulator, dump another 12oz in there, and see where it stabilizes.

engatwork · #74 06-08-2012, 02:54 PM

Maybe he is trying to save the money that the can of r134 cost

.

1980sd · #75 06-09-2012, 09:58 AM

Did 120 miles yesterday with ambient about 85F although it was mid 70's when I got home.

Kind of weird though...

After work it was 110F in the car so I'm all excited about checking out the AC. I fire it up and no AC blower

Check the fuses, servo operation etc. All is well, just no blower.

WTF

While I'm tinkering under the hood I notice the clutch cycling. The aux fan is running and the accumulator is frosting etc. just no AC/heat blower. No defrost blower either which is supposed to ALWAYS work... So I head home defeated

I try the AC with no blower and the compressor still cycles so I give up.

I stop for some Gatorade (No AC right

) and figure I'd Hail-Mary and pull the glovebox and check the blower. A little wiggle of the center shaft and it starts spinning

So I shoot some WD40 on it and head out.

So during the trip I'm pointing a little IR thermometer at the vents. It seems to be the most accurate portable thermometer I have based on tests with ice cubes and boiling water and comparison with a calibrated thermocouple.

Word: My tinkering has revealed a HUGE spread in thermometer readings. I have 2 of those pocket AC thermometers and they are JUNK! I think they make them read high so the parts stores can sell you stuff

Anyway, back to the trip...

No stop-N-go, pretty much 55mph to mystery speeds. (85mph speedo)

The AC is kicking

but I'm getting vent temps in the high 20's

and frost is forming on the metal parts of the vents. I figure if the evap was freezing then airflow would slow and the vent temps would rise (Plus the ETR switch) but nothing seemed to change

My guess is that the charge is low like John said and my evap is freezing solid and air is just blowing AROUND the block of ice instead of through the coil. When I parked condensate was running out the drains for a good hour after I shut her down. I should have turned the blower on with the car sitting to verify but I didn't think about it.

The accumulator had a thin sheen of ice on it when I parked so there HAD to be ice on the evap.

Sooo, should I put another 1/2 can of 134a in it or just leave well enough alone? I'm scared that icing in the evap core will damage something but the ETR NEVER cycled with the blower on

I was thinking that the evap was freezing quickly with the blower off and the air going through it prevented freezing but it sure seems like it was. How else could I have such low vent temps?

Any input, theorizing?