Need Some Advice on A/C -- Not Cold...
03-28-2009, 08:58 PM
#1
Need Some Advice on A/C -- Not Cold...
Briefly:
1. A/C Clutch engages (whines, yes--bearing is bad) when A/C is switched on. I can hear the hissing sound from inside the cabin
2. Pressure on low side dips from ~55 PSI (A/C NOT on) to ~30 PSI (when A/C is switched on)
3. Low Side Pressure never budges from ~30 PSI while A/C is on
4. Air does NOT get cold inside car
5. Low Side return pipe to cooling unit does NOT get cold
6. Pressure rises back to ~55 PSI when A/C is shut off
Any ideas? I am going crazy here. I added some oil/refrigerant today--boosted PSI a few pounds...no change.
1. A/C Clutch engages (whines, yes--bearing is bad) when A/C is switched on. I can hear the hissing sound from inside the cabin
2. Pressure on low side dips from ~55 PSI (A/C NOT on) to ~30 PSI (when A/C is switched on)
3. Low Side Pressure never budges from ~30 PSI while A/C is on
4. Air does NOT get cold inside car
5. Low Side return pipe to cooling unit does NOT get cold
6. Pressure rises back to ~55 PSI when A/C is shut off
Any ideas? I am going crazy here. I added some oil/refrigerant today--boosted PSI a few pounds...no change.
03-29-2009, 01:00 AM
#3
Junior Member
Join Date: Dec 2005
Posts: 22
I had this problem with my old datsun pickup. there's a hose from the evaporator to drain the condensation. If this hose gets plugged, the evaporator fills w/ water, and doesn't cool the air. Usually you can access it from under the passenger side of the dash, detach it, drain it, and clean it.
However, now that I'm looking at my haynes manual, it appears that the evaporator drain isn't a hose, but a tube that goes through the firewall, and you can't access it from the passenger compartment. You have to check it from the engine compartment.
Just make sure you're not laying under that drain when you shove something up there to clean it out.
However, now that I'm looking at my haynes manual, it appears that the evaporator drain isn't a hose, but a tube that goes through the firewall, and you can't access it from the passenger compartment. You have to check it from the engine compartment.
Just make sure you're not laying under that drain when you shove something up there to clean it out.
03-29-2009, 11:43 AM
#4
I had this problem with my old datsun pickup. there's a hose from the evaporator to drain the condensation. If this hose gets plugged, the evaporator fills w/ water, and doesn't cool the air. Usually you can access it from under the passenger side of the dash, detach it, drain it, and clean it.
However, now that I'm looking at my haynes manual, it appears that the evaporator drain isn't a hose, but a tube that goes through the firewall, and you can't access it from the passenger compartment. You have to check it from the engine compartment.
Just make sure you're not laying under that drain when you shove something up there to clean it out.
However, now that I'm looking at my haynes manual, it appears that the evaporator drain isn't a hose, but a tube that goes through the firewall, and you can't access it from the passenger compartment. You have to check it from the engine compartment.
Just make sure you're not laying under that drain when you shove something up there to clean it out.
OP, most likely its the expansion valve. Have you been able to get a pressure reading on the high side?
03-29-2009, 03:47 PM
#5
If you dont have access to a high pressure gauge then use the one you have and rev the engine up to about 2500~3000 rpms and see if the needle drops down into a vacuum(below zero) . if so , probably expansion valve.
03-29-2009, 08:03 PM
#7
03-29-2009, 08:47 PM
#8
Junior Member
Join Date: Dec 2005
Posts: 22
Its a cheap, easy place to start, rather than going to a shop or dealer who's gonna try to do an expansion valve job up front for a couple hundred dollars.
03-30-2009, 12:10 AM
#9
03-30-2009, 06:54 AM
#10
Which is exactly what I said - if that tube gets plugged, the evaporator box fills up with water. It happened to my old datsun, my old subaru, and my friends old Honda. It happens to old cars, and our cars are old now. When I cleared the tube on all of these cars, almost a half-gallon of water drained out.
Its a cheap, easy place to start, rather than going to a shop or dealer who's gonna try to do an expansion valve job up front for a couple hundred dollars.
Its a cheap, easy place to start, rather than going to a shop or dealer who's gonna try to do an expansion valve job up front for a couple hundred dollars.
The OP said the air didnt get cold, not that he had no air blowing. There wouldnt be any airflow at all if the evaporator box was filled with condensate. I have no doubts that the drain tube could probably use a good cleaning. Hell, if it was my car I would recover the refrigerant, pull the evaporator box, and give it a good cleaning and disinfecting(Done it twice).
Most likely whats going on is the TXV is clogged/sticking, or theres a bad valve seal inside the compressor. Not a fun job to fix but not hard to fix. If the compressor turns out to be bad then I would go ahead and replace the TXV and receiver drier while I'm at it...clean the evaporator coil, pull a vacuum, charge it up and enjoy cold, clean-smelling air.
Last time I did this was in my 99. On a 102 degree day and the car running at idle I had 42 degree air coming out of the vents.
04-01-2009, 11:44 AM
#11
...
Most likely whats going on is the TXV is clogged/sticking, or theres a bad valve seal inside the compressor. Not a fun job to fix but not hard to fix. If the compressor turns out to be bad then I would go ahead and replace the TXV and receiver drier while I'm at it...clean the evaporator coil, pull a vacuum, charge it up and enjoy cold, clean-smelling air...
Most likely whats going on is the TXV is clogged/sticking, or theres a bad valve seal inside the compressor. Not a fun job to fix but not hard to fix. If the compressor turns out to be bad then I would go ahead and replace the TXV and receiver drier while I'm at it...clean the evaporator coil, pull a vacuum, charge it up and enjoy cold, clean-smelling air...
I have yet to check high side pressure. I think I might try to but I don't have manifold gauges. No matter what I do, I can't get pressure to budge once the car has started. It only changes when compressor is switched on or off...
04-01-2009, 12:11 PM
#12
TXV is just and acronym for Thermal Expansion Valve.
Let me see if I got this right... You were adding refrigerant to the system with the compressor engaged and the car running but the suction pressure didnt change? It only changed when the AC was on or off?...between 30-55psi?
Just going by this, without a reading on the highside, it sounds like one of three possible things.
1. Expansion valve stuck/closed/not functioning properly.
2. Clogged receiver drier.
3. Bad valve seals internal to the compressor.
Its hard to pinpoint what exactly could be the problem without accurate pressure and temperature readings. I'd hate to tell you it's one thing and it turn out to not fix it. However I will tell you that if you decide to replace the compressor go ahead and change the expansion valve and receiver drier at the same time. When you have it charged up with refrigerant make sure a good vacuum is pulled on the system to evacuate any air and moisture that may be in the lines.
I wish I could help you more, but without physically looking at your car this is the best I can do.
Let me see if I got this right... You were adding refrigerant to the system with the compressor engaged and the car running but the suction pressure didnt change? It only changed when the AC was on or off?...between 30-55psi?
Just going by this, without a reading on the highside, it sounds like one of three possible things.
1. Expansion valve stuck/closed/not functioning properly.
2. Clogged receiver drier.
3. Bad valve seals internal to the compressor.
Its hard to pinpoint what exactly could be the problem without accurate pressure and temperature readings. I'd hate to tell you it's one thing and it turn out to not fix it. However I will tell you that if you decide to replace the compressor go ahead and change the expansion valve and receiver drier at the same time. When you have it charged up with refrigerant make sure a good vacuum is pulled on the system to evacuate any air and moisture that may be in the lines.
I wish I could help you more, but without physically looking at your car this is the best I can do.
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