AC problem
Thread Starter
|
Senior User
Joined: Sep 2003
Posts: 115
Likes: 0
From: Donna
AC problem
I replaced the AC compressor with a Motorcraft unit. The old one leaked behind the pulley which is apparently a common failure point. The old compressor had 172,000 miles on it so I went with new. The AC works great most of the time.
I think I know the conditions when it does not work great but I have not done a scientific study. I might be wrong about a certain condition but here goes.
I run the AC on max cool, we are on the Mexico border about as far south as you can go and be in the US. As long as I keep the blower on 4 the AC does not cut out. If I turn the blower down it will eventually stop cooling until I turn the blower back to 4. It doe not instantly begin cooling but after a few minutes it will start blowing cool again.
When I charged the system the AC manifold gauges read oddly. If just the low side is open it reads correctly, if I opened the high side the low side would peg the gauge beyond the maximum. I think I read that indicates a valve is bad.
Any advice is welcome. I hope there is an AC guru on here!
I think I know the conditions when it does not work great but I have not done a scientific study. I might be wrong about a certain condition but here goes.
I run the AC on max cool, we are on the Mexico border about as far south as you can go and be in the US. As long as I keep the blower on 4 the AC does not cut out. If I turn the blower down it will eventually stop cooling until I turn the blower back to 4. It doe not instantly begin cooling but after a few minutes it will start blowing cool again.
When I charged the system the AC manifold gauges read oddly. If just the low side is open it reads correctly, if I opened the high side the low side would peg the gauge beyond the maximum. I think I read that indicates a valve is bad.
Any advice is welcome. I hope there is an AC guru on here!
Fleet Mechanic
Joined: Jul 2005
Posts: 1,467
Likes: 107
From: Staten Island, NY
What you're describing is a symptom of the evaporator freezing up. When you keep the fan on high, you pass enough hot air across the evaporator coils to keep them from freezing. Slow down the fan and the coils ice up and cooling pretty much stops. Turn the fan up and you basically defrost the coils.
Your gauge readings seem to indicate a bad thermostatic expansion valve. With the system running the low side should be....well...low. If the TXV is bad it is flooding the evaporator with refrigerant and some of that refrigerant is still liquid (and boiling) by the time it reaches the suction line. Not a good thing for the compressor either. They don't like liquid refrigerant in the suction intake.
The TXV is located where the refrigerant lines pass through the firewall. With the system running on a hot day and the fan NOT on high feel the suction line between the firewall and the compressor. It should be warm or COOL. If its COLD its TXV time.
Your gauge readings seem to indicate a bad thermostatic expansion valve. With the system running the low side should be....well...low. If the TXV is bad it is flooding the evaporator with refrigerant and some of that refrigerant is still liquid (and boiling) by the time it reaches the suction line. Not a good thing for the compressor either. They don't like liquid refrigerant in the suction intake.
The TXV is located where the refrigerant lines pass through the firewall. With the system running on a hot day and the fan NOT on high feel the suction line between the firewall and the compressor. It should be warm or COOL. If its COLD its TXV time.
Hotshot
Joined: Jan 2004
Posts: 19,765
Likes: 1,082
From: St Louis
When I charged the system the AC manifold gauges read oddly. If just the low side is open it reads correctly, if I opened the high side the low side would peg the gauge beyond the maximum. I think I read that indicates a valve is bad.
Hotshot
Joined: Jan 2004
Posts: 19,765
Likes: 1,082
From: St Louis
Which valves are your talking about? A typical manifold has a valve for each side that connects it to the center port. Also, there should be a separate valve on each hose near the connector that isolates the connector from the manifold. These, of course, do have to be open to measure anything.
Be specific.
Be specific.
Thread Starter
|
Senior User
Joined: Sep 2003
Posts: 115
Likes: 0
From: Donna
I connect the adapter to thr ports, screw the handle down to open the Schrader valve. I have opened both valves on the manifold body, I guess I misunderstood what I saw in the instructions.
Thread
Thread Starter
Forum
Replies
Last Post
