88-94 5.7 Suburban A/C Diagnosis and Tuning

[cjcb1100]

i kinda noticed the temp diff the other day but i dont remember where it changed i will try that tomorrow

 

[cjcb1100]

update i let some out into a old freon bottle will be recycled

currently at time of readings 106* 20% humidity

@ 2k rpm

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@ idle

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temps

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[cjcb1100]

also cannot feel the condenser for temp change with out removing the grille witch is almost crumbled into pieces

 

[cjcb1100]

condensor is hot at least 1/2 way up maybe more

 

[L31MaxExpress]

For anyone working on AC or cooling systems, an IR Temperature gun is fairly inexpensive and fairly accurate. I would highly recomeend spending $50 or so and investing in one. I have found a couple of GM systems with a restriction in the line. The newer cars and trucks have an expansion valve but also have a refrigerant filter that looks like the inlet side of an old orifice tube. When I found it, I thought to myself, where is the other half of it. I consulted the parts diagram at that point.

 

[cjcb1100]

mine quit working recently and i haven't got another sorry for all the questions every one sorry if i am bothering

 

[Wildblue19]

Got to dedicate a day to the Burb yesterday. My plan was to:

1) Replace the tube-fin condenser back to a parallel flow,
2) Replace the accumulator with the correct, larger one for dual air trucks,
3) Replace the R12 TXV in the rear with a R134 specific one,
4) Add a reciever-drier to the rear system to feed the TXV better quality refrigerant.

I pulled all the old components, and recovered as much oil as I could pour out from them (about 3oz). Oil looked good, no off colors or metal flake.


Assembly

Parallel flow went in no problem, made sure there was no o-tube pre-installed. Put 2oz in there. Accumulator went in fine, other 2oz in there of fresh oil.

Old TXV had a tiny filter screen with a little gunk in it; was hopeful this was contributing to my issues.

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I replaced the TXV with the R134 specific version, which had no internal screen. Rear rebuilt:

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Side note, earlier in the thread I was looking for a body seal for the rear A/C lines; I bought the 95+ one that was posted and it's not even close. Needed to make my own seal:

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Reinstalled the rear A/C box into the truck, then mounted up my mini reciever-drier. Used the same bolts that hold the air box down to mount it, so no drilling required. Was able to adapt the factory lines to work, so it is totally reversible if it doesn't work.

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It also has a sight glass on top so with an inspection mirror I can see inside the system.

Charging

Vacuumed it down for 30 mins, held it there for an hour, got to -13.9 psi. Charged it with two 10oz 152a cans to start, then slowly started adding refrigerant on the 3rd can, feeling the line temperature right after the o-tube and comparing it to the suction line off the accumulator.

Long story short, 3 full cans in and the accumulator suction line never got cold. Added a bit more but it wasn't getting any better, so i stopped around 35oz. And here's the results:

Ambient temp 105°, idle, 15% humidity...

Low side: 65psi
High side: 215psi.

Rear sight glass has some bubbles but isn't foaming, it looks ok.

Now what? The performance is way worse now, somehow.

 

[cjcb1100]

yeah mine is worse as well 105 outside and 68 inside vent, sorry to here wildblue

 

[L31MaxExpress]

Got to dedicate a day to the Burb yesterday. My plan was to:

1) Replace the tube-fin condenser back to a parallel flow,
2) Replace the accumulator with the correct, larger one for dual air trucks,
3) Replace the R12 TXV in the rear with a R134 specific one,
4) Add a reciever-drier to the rear system to feed the TXV better quality refrigerant.

I pulled all the old components, and recovered as much oil as I could pour out from them (about 3oz). Oil looked good, no off colors or metal flake.


Assembly

Parallel flow went in no problem, made sure there was no o-tube pre-installed. Put 2oz in there. Accumulator went in fine, other 2oz in there of fresh oil.

Old TXV had a tiny filter screen with a little gunk in it; was hopeful this was contributing to my issues.

You must be registered for see images attach

I replaced the TXV with the R134 specific version, which had no internal screen. Rear rebuilt:

You must be registered for see images attach

Side note, earlier in the thread I was looking for a body seal for the rear A/C lines; I bought the 95+ one that was posted and it's not even close. Needed to make my own seal:

You must be registered for see images attach

You must be registered for see images attach

Reinstalled the rear A/C box into the truck, then mounted up my mini reciever-drier. Used the same bolts that hold the air box down to mount it, so no drilling required. Was able to adapt the factory lines to work, so it is totally reversible if it doesn't work.

You must be registered for see images attach

It also has a sight glass on top so with an inspection mirror I can see inside the system.

Charging

Vacuumed it down for 30 mins, held it there for an hour, got to -13.9 psi. Charged it with two 10oz 152a cans to start, then slowly started adding refrigerant on the 3rd can, feeling the line temperature right after the o-tube and comparing it to the suction line off the accumulator.

Long story short, 3 full cans in and the accumulator suction line never got cold. Added a bit more but it wasn't getting any better, so i stopped around 35oz. And here's the results:

Ambient temp 105°, idle, 15% humidity...

Low side: 65psi
High side: 215psi.

Rear sight glass has some bubbles but isn't foaming, it looks ok.

Now what? The performance is way worse now, somehow.

My best guess is the reciever dryer probably takes 12oz to fill up to its designed capacity.

 

[L31MaxExpress]

yeah mine is worse as well 105 outside and 68 inside vent, sorry to here wildblue

108F outside, sitting in direct sunlight, and mine just dropped from ~130°F to 55°F in about 3 minutes at idle, recirculating the hot interior air. I reved the engine up a bit (~2,000 rpm) and it dropped to ~50°F before the wrong for the application 275-280 psi cut-off switch cycled the compressor. I still need to swap that switch for the correct 430 psi switch.

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