AC Cools then Stops Cooling

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F

FJ80HI

10 Year
Joined
Mar 4, 2013
Threads
18
Messages
206
On my 91 FJ80 the ac works for 10 mins then stops cooling. Everything keeps running (the fan and compressor). I have verified refer is charged to specs. After the car sits for several hours the ac will work again- for about 10 mins then stop blowing cold air. I did have an ac shop look at it. They verified the charge and the ac worked while at the shop. The shop says the compressor is noisy and say it should be replaced. I am not sure this is the problem. The compressor is spinning (I was thinking may be an ac clutch problem- but that looks to be ok). I am thinking maybe the expansion valve gets clogged then after sitting clears, but then clogs after running ac. Any input appreciated.
Regards
 
Im not sure if a 91 had it but I had a temperature sensor go bad on mine that stopped the AC from working. Iforget what it was caled but its on the drivers side of the block under the intake. Its meant to shut the AC down if the motor begins to oveeheat.
 
The expansion valve is the hardest part of the system to reach. Its not really that hard actually, you can have it out in less then 30 minutes. So if your going to go through the trouble, you may as well just do the rest of the system. I just finished my 97 and it took about 3 hours from start to finish. I would suggest the following :

New o-rings, there are 10 in the system
New Schraeder valve cores 3 in the system
New drier ( this one is a must )
New expansion valve
New compressor top seal
New oil for the compressor and any parts you replace in the system ( it takes PAG46 )

Its maybe a :banana::banana: job at best. Its also cheap insurance that you won't be doing the job again.
 
Stokes said:
Im not sure if a 91 had it but I had a temperature sensor go bad on mine that stopped the AC from working. Iforget what it was caled but its on the drivers side of the block under the intake. Its meant to shut the AC down if the motor begins to oveeheat.
Click to expand...

Or maybe it actually is overheating. the dash temp gauge doesn't really tell you much. I had the same issue (it ws actually overheating) and replaced my radiator. Now my A/C will freeze my face.
 
The most likely suspect is indeed the expansion valve.
 
If you have access to a set of gauges, if the expansion valve is the problem, when it quits cooling, you'll see the low-side pressure go to <5psi and perhaps into vacuum. Replace the drier if you open the system. If it's still an R12 system, it uses ND6 (mineral) oil. You might add an ounce to try and quiet the compressor.
 
1972FJ55 said:
If you have access to a set of gauges, if the expansion valve is the problem, when it quits cooling, you'll see the low-side pressure go to <5psi and perhaps into vacuum. Replace the drier if you open the system. If it's still an R12 system, it uses ND6 (mineral) oil. You might add an ounce to try and quiet the compressor.
Click to expand...
Maybe it is not the expansion valve. My pressures on the low side remains at about 30 psi (system has been converted to R134A). Could a clogged filter drier cause the intermittent cooling problem?
 
FJ80HI said:
Maybe it is not the expansion valve. My pressures on the low side remains at about 30 psi (system has been converted to R134A). Could a clogged filter drier cause the intermittent cooling problem?
Click to expand...

Is that the low-side with the system not cooling? What's the high-side when it's not cooling?
 
1972FJ55 said:
Is that the low-side with the system not cooling? What's the high-side when it's not cooling?
Click to expand...
The low side is around 30 psi when cooling, and also stays at 30 when not cooling. I am not sure what the high side is as I do not have a gauge. When at the AC shop the high and low were within range (but the ac continued to cool the air, so not sure what the high is when stops blowin cool air). I guess I should get a high side gage or pull into the shop when the ac starts blowing warm.
 
1972FJ55 said:
30 is a little high for the low-side, normally it's around 25. I'm wondering if there's a possibility of it being overcharged and/or the fan clutch is being lazy.
Click to expand...
I lowered the low side pressure to 25 psi and the ac cooled for 10 minutes then stopped cooling. When it was blowing cold air it was not as cold as when at 30 psi low side. I might try to pick up some high side press gauge today and run some more test. Will post results.
Thanks for the input.
Has anyone ever had a clogged ac filter dryer and if so, what effect does it have on the ac?
 
It would clog at Expansion valve (much smaller orifice) before plugging dryer/accumulator
 
I think the problem is the expansion valve. I ordered a complete gauge set and ran the ac. The ac would work good for say 5 minutes then stop cooling. When the cooling stopped the high pressure side would go up to 300 psi and low side could go to near 0 psi (this would indicate the compressor is still good). When this happened I looked at the sight glass and saw no flow (where as I had flow when ac was cooling) I felt the refer lines and drier and found no cold spots which indicates the plug is probably at the expansion valve. I have a new drier and vavle and have a vac pump on order. Will replace the drier and expansion valve as well as some orings when I get some time.

Does anyone know if there is a pressure relief vavle on the ac compressor? A year ago I was filling the system and for a split second I had a large discharge of refergerant. But after that there were no leaks and the ac worked well.
Regards
 
It has been a while, but just wanted to follow up on this thread. I replaced the expansion (and the AC/Drier filter) valve 18 months ago and the AC has been running great ever since- that was the problem.
 
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