Automotive Air Conditioning Information Forum (Archives)

Oswalla on Tue August 12, 2014 11:33 PM

Year: 1990
Make: jeep
Model: cherokee
Engine Size: I6
Refrigerant Type: 134a
Ambient Temp: 84
Pressure Low: 0
Pressure High: 60
Country of Origin: United States

Pulled vacuum, pressure held no leaks. I added dye before closing system up, No leaks after refill either. Added 1 can 12oz. through high side liquid method, closed off high. Started motor, compressor kicked on and stayed on the whole time. But my LOW was 0 or negative UNLESS I inverted can upside down, liquid method, Then it would hit the desired 20 or so on low side. The high side never wavered of 60. Service valves were open.

Let me have it, I'm sure I messed something up. Or that compressor is just not compressing. How do you check for that ?

Dougflas on Wed August 13, 2014 6:35 AM

The handwheels on the manifold need to be closed while the engine is running, especially the high side. What are the pressures with both handwheels closed after the correct amount of freon is installed in the system?

mk378 on Wed August 13, 2014 10:28 AM

Those results are typical for having only one can in. You need to look at the specs for how much refrigerant to use. With a converted system charge in about 90% of the weight they say to use for R-12 and then start checking the pressures and performance. Was it running 134a before or did you just convert it?

Oswalla on Wed August 13, 2014 10:29 AM

I closed both before starting motor. I then started and got 2nd can hooked up and opened low side. High was 60 the whole time never moved, Low would only go up when adding freon then back to zero. Service valves were mid seated per FSM. I have those valves where The compressor can be isolated for servicing without losing system coolant.

If I never open Low side wheel on gauge manifold how does the gas get in the system.

wptski on Wed August 13, 2014 10:35 AM

Quote
Originally posted by: Oswalla

If I never open Low side wheel on gauge manifold how does the gas get in the system.
As you described, it can't!



Edited: Wed August 13, 2014 at 10:38 AM by wptski

Oswalla on Wed August 13, 2014 10:40 AM

Quote
Originally posted by: mk378
Those results are typical for having only one can in. You need to look at the specs for how much refrigerant to use. With a converted system charge in about 90% of the weight they say to use for R-12 and then start checking the pressures and performance. Was it running 134a before or did you just convert it?

Yeh a conversion to 134a. I know thats what it seem like but I have 3 empty cans that went in. R12 specs is 38oz. and roughly 80% for 134a is 30oz. of 134a, and I probably lost a percent when purging line with each new can of 134a. So I should be overcharged, but my pressures sure dont show that. I figured I would have some pressure readings to gage when to stop that 3rd can.

Oh and performance is none. vent temp 84 after vacuum down, pre chargeing and 94 when 3rd can complete.


Edited: Wed August 13, 2014 at 10:47 AM by Oswalla

wptski on Wed August 13, 2014 3:41 PM

Quote
Originally posted by: Oswalla
Quote

Originally posted by: mk378

Those results are typical for having only one can in. You need to look at the specs for how much refrigerant to use. With a converted system charge in about 90% of the weight they say to use for R-12 and then start checking the pressures and performance. Was it running 134a before or did you just convert it?

Yeh a conversion to 134a. I know thats what it seem like but I have 3 empty cans that went in. R12 specs is 38oz. and roughly 80% for 134a is 30oz. of 134a, and I probably lost a percent when purging line with each new can of 134a. So I should be overcharged, but my pressures sure dont show that. I figured I would have some pressure readings to gage when to stop that 3rd can.

Oh and performance is none. vent temp 84 after vacuum down, pre chargeing and 94 when 3rd can complete.
It could be leaking as fast as it's going in. In the land of HVAC, vacuuming is not used as a primary leak test, pressure is and done first. It may hold a vacuum but leak under pressure or vise versa. It's a pressure system not a vacuum system. I had this happen to me, held a vacuum but wouldn't hold one can of R12. I pulled the compressor, replaced the shaft seal, replaced the accumulator and converted to R134A. That was last summer, driven only once. My family backup vehicle, this spring found a puddle of oil. Supposedly, new seals can leak and need a break in time. Got a nitrogen setup, held at 150psi for days, held vacuum using a micron gauge for days and freezes me out! Nothing dripping so far....

mk378 on Wed August 13, 2014 6:31 PM

With engine off, the pressure should equalize to about the saturation pressure for your ambient temperature. If they both go down to zero, like wptski said, it is all leaking out.

With a full charge, low side going to zero or negative when the compressor starts suggests a blockage, the most likely place is the TXV being stuck closed. Also make sure you didn't turn the isolation valve too far and close off the hose from the evaporator. You just need to crack it open a little off of the back seat in order to open the service port.

But with a blockage the high side should be higher, again about the saturation pressure for the condenser temperature, since all your refrigerant is going to be sitting in the condenser as liquid. This is a lower high side than normal operation but at 84 degrees it would be more than 60.

Edited: Wed August 13, 2014 at 6:33 PM by mk378

Oswalla on Thu August 14, 2014 1:53 PM

Quote


It could be leaking as fast as it's going in. In the land of HVAC, vacuuming is not used as a primary leak test, pressure is and done first. It may hold a vacuum but leak under pressure or vise versa. It's a pressure system not a vacuum system. I had this happen to me, held a vacuum but wouldn't hold one can of R12. I pulled the compressor, replaced the shaft seal, replaced the accumulator and converted to R134A. That was last summer, driven only once. My family backup vehicle, this spring found a puddle of oil. Supposedly, new seals can leak and need a break in time. Got a nitrogen setup, held at 150psi for days, held vacuum using a micron gauge for days and freezes me out! Nothing dripping so far....

I see what you mean with pressurizing versus vacuum, but wouldn't the dye I put in get circulated and show the leak. I put dye in when adding oil but not in the compressor. Maybe not since the oil is moved my the freon, correct.

I should add I replaced the accumalator and expansion valve. Flushed evaporator when expansion valve was off and condensor as well. Afterwards I blew out all parts with 120 psi air and had good air flow through out before reassembly.

Oswalla on Thu August 14, 2014 2:09 PM

Quote
Originally posted by: mk378
With engine off, the pressure should equalize to about the saturation pressure for your ambient temperature. If they both go down to zero, like wptski said, it is all leaking out.



With a full charge, low side going to zero or negative when the compressor starts suggests a blockage, the most likely place is the TXV being stuck closed. Also make sure you didn't turn the isolation valve too far and close off the hose from the evaporator. You just need to crack it open a little off of the back seat in order to open the service port.



But with a blockage the high side should be higher, again about the saturation pressure for the condenser temperature, since all your refrigerant is going to be sitting in the condenser as liquid. This is a lower high side than normal operation but at 84 degrees it would be more than 60.

I suppose its possible I got a bad expansion valve causing blockage. Looked exactly like old one which was working, figured since I had it apart it wouldn't hurt putting the new one on I had anyways.

Service ports : I am going by my Jeep FSM for seating, it says front seating is closed and to open to a mid seat for filling and back seat I believe said was for isolation. I opened from front seat about 6 1/4 turns with total back seat being about 22 1/4 turns. I will double check this info but my valves were definately front seated when I started.

I will get back to working on it tomorrow and check for leaking dye that I did not see initially. Any other things to check before I order a new compressor.

Dougflas on Thu August 14, 2014 2:29 PM

I had a new ezpansion valve stick closed. I smacked it with a screwdriver and it worked for over 4 years; the guy changed vehicles so I do not know how long it lasted. It was a block type on a Chysler product.

wptski on Thu August 14, 2014 8:11 PM

Quote
Originally posted by: Oswalla
Quote


I see what you mean with pressurizing versus vacuum, but wouldn't the dye I put in get circulated and show the leak. I put dye in when adding oil but not in the compressor. Maybe not since the oil is moved my the freon, correct.

I should add I replaced the accumalator and expansion valve. Flushed evaporator when expansion valve was off and condensor as well. Afterwards I blew out all parts with 120 psi air and had good air flow through out before reassembly.
I remember reading here that dye only works if the system is fully charged.

Oswalla on Thu August 14, 2014 9:02 PM

Quote
Originally posted by: Dougflas
I had a new ezpansion valve stick closed. I smacked it with a screwdriver and it worked for over 4 years; the guy changed vehicles so I do not know how long it lasted. It was a block type on a Chysler product.

I've been wanting use a hammer on it, now I know what to hit.