87 R10 A/c Problem

jblakeney · July 5, 2011

Hey guys,

I have a question I have not figured out quite yet.... If nobody knows what should be going on here I will pull the box out on the inside and have a good look and figure it out.... But I'm hoping to save some time and pulling the inner fender on the passengers side and the box on the inside.........

The attached picture is of the recirculation door (I am talking about #15). I think? It appears to function as that in my truck, when MAX A/C is demanded the door opens.... When vent is called for it closes...

When this door is open where does the air turn around into? The Cowl? How does it get back around to the evaporator core?????

This is the first time I have drove my truck in the Mississippi summer heat..... The A/C had trouble in the fall....

I am sweating like crazy on the accumulator, and have near same inlet and outlet temps on the evaporator.... so I am experiencing some sort of A/C case wind leak. I used seam sealer around on the under hood portion of the case and got all of my leaks stopped out under the hood. However, the temp inside the cab on Max A/C (which should be recirculation) are not what I should be getting according the the evaporator temps...... It is like I am getting a fresh air leak.

It is about to drive me insane.... its not the compressor or a restriction in the system..... Pressures (high and low) are right on for the ambient temp......... But instead being over taxed at the evaporator, like it is having to much fresh air.

Any help would be appreciated,

Jbo

txab · July 5, 2011

Any chance your getting heat from the heater core?

ChevyTech77 · July 5, 2011

If memory serves me correctly, that truck should have a vacuum operated heater control valve to shut the hot water off from coming into the heater core. I could be wrong though.

Also, you never stated what your ambient temperature, relative humidity and outlet temperatures are. You may be within spec but are just not happy with the systems performance too.

Does the system cool well with the a/c set to norm or bi-level?

Recirculation will pull fresh air from the cabin of the vehicle and recirculate it back through the hvac case hense the name, recirculation.

Could just be a temp door not going full cold when commanded to do so.

jblakeney · July 5, 2011

Did not have a valve to start with. I added a manual cut off valve in the fall.....

I am good on high and low pressure according the the ambient temp. However, it is like I have a good leak of fresh air..... Max is the same as Norm...

I am experience an air handling problem........... The vent temp does not change. Evaporator and accumulator is sweating to the point it has to be an air leak.

Jbo

jblakeney · July 25, 2011

Ok, Friday it was slow at work so I pulled the truck in the back and check the pressures and wrote them down.... Its been busy hadn't had time to do this, till Friday...

Low Side - 18psi

High Side - 151psi

Ambient Temp - 80 F (or a tad less, its south Mississippi so you can guess the humility level, NICE AND really sticky or 90+%)

Pulled the noise of the truck inside and did this, so no SUN LOAD.

Evaporator Inlet Temp - 16 F (as per my fluke meter)

Evaporator Outlet Temp - 18 F (as per my fluke meter)

Duct Temp - 66 F (as per digital air temp gauge stuck in first vent from evaporator, System in MAX AC MODE, no change in temp for Norm, only vent pressure)

System Ran for 15 minutes before I took the readings with the doors shut and windows up.

The recirculate door in the passengers kick panel shuts allowing only cabin air to circulate in the evap box, the doors inside the truck are in the right spot according to the book, but I have not tore down the cowl to find out about the one in the cowl.

As I said before the pressures and temps are good on the system, just not in the duct temp.

The temp of the evaporator inlet and outlet being 16 F in and 18 F out, means it should have been almost, ice coming from the vents. Dryer and suction line dripping wet with sweat and making large POOL under the truck.

Any help appreciated,

Jbo

No water in heater core. Two valves both closed.

Neither my 86 which my Dad bought new or my 87 has a vacuum valve for the heater core. The doors in the 87 under the dash operate the same as the 86. The 86 works perfect, regular R12 refrigerator.

jblakeney · September 7, 2011

Fixed,.............

After removing socket from the door leading from the evaporator core air path. That had the door jammed partly open, ie maybe 2 inches....... Apparently, at some point somebody went in and changed the air distribution plastic connector on the door...... It was new and aftermarket. No, GM markings... They left me a Kobalt 8mm 1/4 drive socket......

All is well and yesterday, when it was almost 90, pulled it out in the sun and the duct temp got down to the 48 degrees and the dryer produced a thin coating of ice (dryer was 30).... And an accumulation of white frost on the back 3 windows......

I love R12.