AC Clutch
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
AC Clutch
AC problem - AC Clutch or Compressor or both.
The AC on my 94 Coupe bogs the engine down when the AC is turned on. If I unplug the AC at the plug on the compressor the engine spins freely. Plug it in and the engine bogs down again (with the switch on). Also the AC clutch seems to wobble slightly when engaged. The clutch will spin freely when the AC is turned off and engages properly when turned on. If I had unlimited funds right now I would buy a new compressor and a new clutch and call it a day. But money is tight right now...
The AC blows cool when turned on but I get a vibration when the AC is turned on.
I have another compressor and with clutch. I really don't know the history on the part but it appears to have lived an easier life than my AC compressor. Just not sure if it was stored properly before I got it.
I believe I can handle changing out the clutch but I can't do the compressor. I may be overly optimistic hoping for the clutch I am afraid. Local shop will change out the compressors for me for $200 using my spare.
Should have already pulled the belt off and checked to see what spins freely but I have a Camber Brace on the car and it is a pain to take off
I have searched a few AC threads but no one has had the bogging symptoms.
Anyone else had this issue?
The AC on my 94 Coupe bogs the engine down when the AC is turned on. If I unplug the AC at the plug on the compressor the engine spins freely. Plug it in and the engine bogs down again (with the switch on). Also the AC clutch seems to wobble slightly when engaged. The clutch will spin freely when the AC is turned off and engages properly when turned on. If I had unlimited funds right now I would buy a new compressor and a new clutch and call it a day. But money is tight right now...
The AC blows cool when turned on but I get a vibration when the AC is turned on.
I have another compressor and with clutch. I really don't know the history on the part but it appears to have lived an easier life than my AC compressor. Just not sure if it was stored properly before I got it.
I believe I can handle changing out the clutch but I can't do the compressor. I may be overly optimistic hoping for the clutch I am afraid. Local shop will change out the compressors for me for $200 using my spare.
Should have already pulled the belt off and checked to see what spins freely but I have a Camber Brace on the car and it is a pain to take off
I have searched a few AC threads but no one has had the bogging symptoms.
Anyone else had this issue?
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
bearing
The compressor front bearing is probably the culprit. Here is the problem.
A. If you don't use the A/C you will roast.
B. If you use the compressor, you risk filling up your A/C system with trash when the bearing or piston goes
C. If you run it till it fails, you may never get the A/C system cleaned again even with a flush.
short term fix:
D. use your spare and install it, even though you may have to add freon every week, it won't come apart since the seals are for holding in the freon and not an operational component and the spare unit still has it's internal integrity.....
Hint:
someone will trade you your camber brace for a good compressor, and when you are flush again, go buy another camber brace since you really don't need it to get to work and back.
your predicament is kinda like this:
The farmer has a boat, and in the boat he has to transport across the river a chicken, a bag of grain and a fox. how is he going to get all three across the river if he can only take 2 items at once..........the chicken eats the grain, and the fox eats the chicken and the fox will run away if the farmer isn't there......
A. If you don't use the A/C you will roast.
B. If you use the compressor, you risk filling up your A/C system with trash when the bearing or piston goes
C. If you run it till it fails, you may never get the A/C system cleaned again even with a flush.
short term fix:
D. use your spare and install it, even though you may have to add freon every week, it won't come apart since the seals are for holding in the freon and not an operational component and the spare unit still has it's internal integrity.....
Hint:
someone will trade you your camber brace for a good compressor, and when you are flush again, go buy another camber brace since you really don't need it to get to work and back.
your predicament is kinda like this:
The farmer has a boat, and in the boat he has to transport across the river a chicken, a bag of grain and a fox. how is he going to get all three across the river if he can only take 2 items at once..........the chicken eats the grain, and the fox eats the chicken and the fox will run away if the farmer isn't there......
Last edited by coupeguy2001; Aug 28, 2008 at 11:32 PM.
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
The compressor front bearing is probably the culprit. Here is the problem.
A. If you don't use the A/C you will roast.
B. If you use the compressor, you risk filling up your A/C system with trash when the bearing or piston goes
C. If you run it till it fails, you may never get the A/C system cleaned again even with a flush.
short term fix:
D. use your spare and install it, even though you may have to add freon every week, it won't come apart since the seals are for holding in the freon and not an operational component and the spare unit still has it's internal integrity.....
Hint:
someone will trade you your camber brace for a good compressor, and when you are flush again, go buy another camber brace since you really don't need it to get to work and back.
your predicament is kinda like this:
The farmer has a boat, and in the boat he has to transport across the river a chicken, a bag of grain and a fox. how is he going to get all three across the river if he can only take 2 items at once..........the chicken eats the grain, and the fox eats the chicken and the fox will run away if the farmer isn't there......
A. If you don't use the A/C you will roast.
B. If you use the compressor, you risk filling up your A/C system with trash when the bearing or piston goes
C. If you run it till it fails, you may never get the A/C system cleaned again even with a flush.
short term fix:
D. use your spare and install it, even though you may have to add freon every week, it won't come apart since the seals are for holding in the freon and not an operational component and the spare unit still has it's internal integrity.....
Hint:
someone will trade you your camber brace for a good compressor, and when you are flush again, go buy another camber brace since you really don't need it to get to work and back.
your predicament is kinda like this:
The farmer has a boat, and in the boat he has to transport across the river a chicken, a bag of grain and a fox. how is he going to get all three across the river if he can only take 2 items at once..........the chicken eats the grain, and the fox eats the chicken and the fox will run away if the farmer isn't there......
Time to save for a new compressor!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
Clutch bearing is pressed into the pulley and if it fails, nothing is going to get into the system. That's not to say that you don't have a compressor that's about to seize and if it does, it will muck things up.
I would scan it to make sure the PCM is reacting to the a/c signal. You should see an increase in IAC counts, pulse width and load variable (if used) - otherwise MAP signal.
Swapping clutches, though a challenge on the LT motors because the main hose assembly is in front of the clutch, isn't difficult. Grab the outer hub with a strap wrench or an oil filter wrench and remove the 10 mm nut. Gently pry off the outer hub and keep your hand underneath it to catch any shims. The Pulley and Coil are retained with snap rings. Installation is the reverse and you'll need to make sure that the outer hub is shimmed so that there's an air gap of .020 inch between it and the pulley. Shim kits are 9 to 12 Bucks at NAPA or GM. Retorque the retaining bolt to 10 ft/lbs. Don't go ape on it as that can damage the shaft seal or crush the shims.
I would scan it to make sure the PCM is reacting to the a/c signal. You should see an increase in IAC counts, pulse width and load variable (if used) - otherwise MAP signal.
Swapping clutches, though a challenge on the LT motors because the main hose assembly is in front of the clutch, isn't difficult. Grab the outer hub with a strap wrench or an oil filter wrench and remove the 10 mm nut. Gently pry off the outer hub and keep your hand underneath it to catch any shims. The Pulley and Coil are retained with snap rings. Installation is the reverse and you'll need to make sure that the outer hub is shimmed so that there's an air gap of .020 inch between it and the pulley. Shim kits are 9 to 12 Bucks at NAPA or GM. Retorque the retaining bolt to 10 ft/lbs. Don't go ape on it as that can damage the shaft seal or crush the shims.
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
Clutch bearing is pressed into the pulley and if it fails, nothing is going to get into the system. That's not to say that you don't have a compressor that's about to seize and if it does, it will muck things up.
I would scan it to make sure the PCM is reacting to the a/c signal. You should see an increase in IAC counts, pulse width and load variable (if used) - otherwise MAP signal.
Swapping clutches, though a challenge on the LT motors because the main hose assembly is in front of the clutch, isn't difficult. Grab the outer hub with a strap wrench or an oil filter wrench and remove the 10 mm nut. Gently pry off the outer hub and keep your hand underneath it to catch any shims. The Pulley and Coil are retained with snap rings. Installation is the reverse and you'll need to make sure that the outer hub is shimmed so that there's an air gap of .020 inch between it and the pulley. Shim kits are 9 to 12 Bucks at NAPA or GM. Retorque the retaining bolt to 10 ft/lbs. Don't go ape on it as that can damage the shaft seal or crush the shims.
I would scan it to make sure the PCM is reacting to the a/c signal. You should see an increase in IAC counts, pulse width and load variable (if used) - otherwise MAP signal.
Swapping clutches, though a challenge on the LT motors because the main hose assembly is in front of the clutch, isn't difficult. Grab the outer hub with a strap wrench or an oil filter wrench and remove the 10 mm nut. Gently pry off the outer hub and keep your hand underneath it to catch any shims. The Pulley and Coil are retained with snap rings. Installation is the reverse and you'll need to make sure that the outer hub is shimmed so that there's an air gap of .020 inch between it and the pulley. Shim kits are 9 to 12 Bucks at NAPA or GM. Retorque the retaining bolt to 10 ft/lbs. Don't go ape on it as that can damage the shaft seal or crush the shims.
"I would scan it to make sure the PCM is reacting to the a/c signal. You should see an increase in IAC counts, pulse width and load variable (if used) - otherwise MAP signal."
I am not sure what you are saying here! Break it down for me pls!
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
The controls - or PCM - are designed to compensate for compressor loading; otherwise the engine will surge or stall. The a/c signal, for your Year, is sent to the PCM which drives (grounds) the compressor clutch relay. To make that transition as seamless as possible, the PCM is programmed to raise idle speed (by opening the IAC valve to allow in more air) and pulse width (injector on time) a nano second before the Relay is grounded. With your scanner, you can track the IAC opening or counts with the a/c off and then on. Most, with the a/c off, have IAC counts in the area of 10 to 15. With the a/c on, that number should increase by 10 or so - the important thing being that it increases. Ditto for injector pulse width. The extra air and loading takes more fuel - make sure it increases. Your load variable is from the MAP sensor - again it's number should go up. Finally, the PCM is Targeting a specific RPM and the design is to keep the Engines's actual idle within 50 rpms of that Targeted Number (Drive) or 100 rpms (Park/Neutral). With the increase in idle counts and fuel, that number should remain steady between a/c and non a/c operation. When it doesn't and everything else shows an increase, that can indicate that compressor loading exceeds the design parameters - ie, it needs a new clutch or a compressor. If the numbers aren't doing anything, than you more than likely need a new PCM or there's some fault in the wiring somewhere - usually too much resistance or bum connectors.
Thread Starter
Melting Slicks
Joined: Feb 2005
Posts: 3,204
Likes: 4
From: Midland Georgia
St. Jude Donor '06
The controls - or PCM - are designed to compensate for compressor loading; otherwise the engine will surge or stall. The a/c signal, for your Year, is sent to the PCM which drives (grounds) the compressor clutch relay. To make that transition as seamless as possible, the PCM is programmed to raise idle speed (by opening the IAC valve to allow in more air) and pulse width (injector on time) a nano second before the Relay is grounded. With your scanner, you can track the IAC opening or counts with the a/c off and then on. Most, with the a/c off, have IAC counts in the area of 10 to 15. With the a/c on, that number should increase by 10 or so - the important thing being that it increases. Ditto for injector pulse width. The extra air and loading takes more fuel - make sure it increases. Your load variable is from the MAP sensor - again it's number should go up. Finally, the PCM is Targeting a specific RPM and the design is to keep the Engines's actual idle within 50 rpms of that Targeted Number (Drive) or 100 rpms (Park/Neutral). With the increase in idle counts and fuel, that number should remain steady between a/c and non a/c operation. When it doesn't and everything else shows an increase, that can indicate that compressor loading exceeds the design parameters - ie, it needs a new clutch or a compressor. If the numbers aren't doing anything, than you more than likely need a new PCM or there's some fault in the wiring somewhere - usually too much resistance or bum connectors.
