AC quits working when hot
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AC quits working when hot
OK here is my problem
I have a 1997 E-150 Van
The ac works fine most of the time.
On very hot days 90+ it shuts down.
It will run for about 20 minutes cycling properly.
Then the compressor starts shutting off for longer and longer cyles
The fan runs but not the compressor.
When I pop the hood the compressor is off.
If I shut off the truck for a while it will run again.
I jumped out both pressure switchs, no help.
Is there a relay that may be failing when hot?
The blower fan runs fine and all the vents work properly.
This is hard to trouble shoot because it only hapens on very hot days.
Thanks
Dave
I have a 1997 E-150 Van
The ac works fine most of the time.
On very hot days 90+ it shuts down.
It will run for about 20 minutes cycling properly.
Then the compressor starts shutting off for longer and longer cyles
The fan runs but not the compressor.
When I pop the hood the compressor is off.
If I shut off the truck for a while it will run again.
I jumped out both pressure switchs, no help.
Is there a relay that may be failing when hot?
The blower fan runs fine and all the vents work properly.
This is hard to trouble shoot because it only hapens on very hot days.
Thanks
Dave
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
For this problem, you really need to know the high and low side pressures. Because it happens at high ambient temps, it sounds like the system is hitting the high pressure limit and shutting down. This is usually caused by a weak fan clutch or dirty condenser. Another cause of excess high pressure is the orifice tube is partially blocked due to a compressor starting to fail (shedding it's rings and metal particles).
This can also be caused by an engine that is near overheating. The PCM logic turns off the AC at a set engine temp to take load off of the cooling system. The EEC system will also shut the AC down in certain failure modes, with or without driveability concerns.
My money is on the fan clutch. If you don't have access to AC gauges this would be the place to start. If you replace it, get an OEM clutch or aftermarket AC Delco. In my experience other aftermarket fan clutches are little better than a weak OEM clutch.
Hope this helps.
PS. Be careful jumping the High Pressure Cutout Switch. Many of them are a trinary switch and jumping the wrong terminals can damage your PCM. It's ok to jump the Low side switch on the accumulator tank.
This can also be caused by an engine that is near overheating. The PCM logic turns off the AC at a set engine temp to take load off of the cooling system. The EEC system will also shut the AC down in certain failure modes, with or without driveability concerns.
My money is on the fan clutch. If you don't have access to AC gauges this would be the place to start. If you replace it, get an OEM clutch or aftermarket AC Delco. In my experience other aftermarket fan clutches are little better than a weak OEM clutch.
Hope this helps.
PS. Be careful jumping the High Pressure Cutout Switch. Many of them are a trinary switch and jumping the wrong terminals can damage your PCM. It's ok to jump the Low side switch on the accumulator tank.
Thread Starter
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Freshman User
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I think I have a weak clutch. The clutch is energized, but the compressor is not turning. I can feel the magnetic feild with a screwdriver. If I help turn the pulley the clutch will engage. Are there any moving parts in a clutch ? or is it a complete electromagnet.
Fleet Mechanic
Joined: Feb 2006
Posts: 1,776
Likes: 5
From: Lorain County, Ohio
The clutch air gap is too wide. The clutch has worn a bit and now the magnetic field is'nt enough to pull the clutch into the pulley. Take the center bolt (8mm head) out of the clutch. There should be shims in the clutch where it slips over the compressor shaft. Remove a shim and check the gap, it should be .010-.020.
To remove the bolt, energize the clutch by jumpering the clutch coil to the battery.
To remove the bolt, energize the clutch by jumpering the clutch coil to the battery.
Hotshot
Joined: Jan 2004
Posts: 19,768
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From: St Louis
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Right on the money.
My air gap is about .040-.050
Looks like I need to remove some shims.
Thanks
Dave
My air gap is about .040-.050
Looks like I need to remove some shims.
Thanks
Dave
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Thread Starter
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Freshman User
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I removed a shim and the AC is ok again.
Very easy repair, only have to take the clutch cover off and remove a shim. You don't even have to touch the belts. I used a straight edge across the face to hold the clutch from turning.
Many Thanks
Dave
Very easy repair, only have to take the clutch cover off and remove a shim. You don't even have to touch the belts. I used a straight edge across the face to hold the clutch from turning.
Many Thanks
Dave
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