A/C Compressor Clutch Failed or Electrical Prob?
08-05-2002, 04:10 PM
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A/C Compressor Clutch Failed or Electrical Prob?
I was trying to charge my 86.5 A/C system yesterday and the compressor was doing some weird things. Started with system nearly empty. Started the car and hooked up the charging manifold. Low side was about 20 at first, high side was almost non-existent. The compressor would slightly cycle slowly a few times. But mostly it sat idle. The high pressure side went up to about 80. The low pressure side got way up to 100, sometimes dropping to 90 if the comporessor cycled a bit. I tried to jump the clutch to see if would work but didn't have a jump wire. I just unpluged the two spade connectors and touched them together. Nothing. I have previously jumped the compressor clutch one time for a few secinds and it worked fine. This time nothing. Could it be the clutch went out? Could it be there is a short in the power to the compressor clutch? When the system is that low, doesn't the compressor signal it's being charged and tries to run to cycle up the system? What could I be doing wrong?
Thanks in Advance,
JE
<img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
Thanks in Advance,
JE
<img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" /> <img src="graemlins/drink.gif" border="0" alt="[cherrsagai]" />
08-06-2002, 01:18 PM
#3
Three Wheelin'
[quote]The high pressure side went up to about 80. The low pressure side got way up to 100, sometimes dropping to 90 if the comporessor cycled a bit. <hr></blockquote>
Static pressure. When the compressor is not running, this is normal. If the compressor runs for a while, the low side should come down, providing the system is in decent shape.
[quote]I tried to jump the clutch to see if would work but didn't have a jump wire. I just unpluged the two spade connectors and touched them together. <hr></blockquote>
Your are supposed to jump the low pressure cut-off switch wires. On the drier, near the middle of the bottle. Easier to get to them through the grille. Use needle-nose pliers or a single aligator clip. Clutch should engage and compessor should turn. If not, let me know.
[quote]When the system is that low, doesn't the compressor signal it's being charged and tries to run to cycle up the system? <hr></blockquote>
No. In fact, if the system is low, the low-pressure cut-off switch stops the compressor to prevent damage.
Here are some questions I need answered to be able to help you.
What freon are you charging the system with?
Did you add any oil (I'm not telling you to add oil, I'm asking if you already have)?
Do you know the history of the system as far as attempted charging, R134 conversion attempts, etc?
Has the system worked in the past?
Let's start with these questions before we try anything related to firing up the system.
HTH
Greg
Static pressure. When the compressor is not running, this is normal. If the compressor runs for a while, the low side should come down, providing the system is in decent shape.
[quote]I tried to jump the clutch to see if would work but didn't have a jump wire. I just unpluged the two spade connectors and touched them together. <hr></blockquote>
Your are supposed to jump the low pressure cut-off switch wires. On the drier, near the middle of the bottle. Easier to get to them through the grille. Use needle-nose pliers or a single aligator clip. Clutch should engage and compessor should turn. If not, let me know.
[quote]When the system is that low, doesn't the compressor signal it's being charged and tries to run to cycle up the system? <hr></blockquote>
No. In fact, if the system is low, the low-pressure cut-off switch stops the compressor to prevent damage.
Here are some questions I need answered to be able to help you.
What freon are you charging the system with?
Did you add any oil (I'm not telling you to add oil, I'm asking if you already have)?
Do you know the history of the system as far as attempted charging, R134 conversion attempts, etc?
Has the system worked in the past?
Let's start with these questions before we try anything related to firing up the system.
HTH
Greg
08-06-2002, 02:31 PM
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Greg,
The system was converted to R-134a at some time. Didn't work when I got the car. System was vacuum evacuated recently and held vacuum. No additonal oil was added. As I said I tried to jump the compressor by unpluging the two spade connectors (pressure switch on side, not temp switch) and touching them together. Nothing happened. However, the compressor will slowly cycle. I saw that happen when I first started charging it. That is why I thought it was acting wierd and wondered if there was something in the low pressure side than sensed charging. Now since I have seen the compressor slowly cycle, I am wondering if there is power getting to the compressor clutch. I noted originally that I sucessfully jumped the compressor shortly after purchasing it. Now I'm looking for a way to double check the compressor is not getting power(i.e. power the clutch at the compressor, not by jumping the pressure switch). Then I would know if the clutch had actually failed, right?
Regards,
The system was converted to R-134a at some time. Didn't work when I got the car. System was vacuum evacuated recently and held vacuum. No additonal oil was added. As I said I tried to jump the compressor by unpluging the two spade connectors (pressure switch on side, not temp switch) and touching them together. Nothing happened. However, the compressor will slowly cycle. I saw that happen when I first started charging it. That is why I thought it was acting wierd and wondered if there was something in the low pressure side than sensed charging. Now since I have seen the compressor slowly cycle, I am wondering if there is power getting to the compressor clutch. I noted originally that I sucessfully jumped the compressor shortly after purchasing it. Now I'm looking for a way to double check the compressor is not getting power(i.e. power the clutch at the compressor, not by jumping the pressure switch). Then I would know if the clutch had actually failed, right?
Regards,
08-06-2002, 03:31 PM
#5
Three Wheelin'
Find the hot line running to the clutch. On my car, there is a disconnect located in the area of the passenger (US) timing belt cover, near the top. The single line leaves the wiring harness.
Measure the resistance of the clutch coil be unplugging the line going to it and use an ohm meter, measuring the line to the compressor to ground. I have to check on the proper resistance value, I have it written down somewhere, I'll look for it for you.
The next step is to check the voltage going to the compressor clutch. Jump the low pressure switch, Unhook the line mentioned above and check voltage on the line coming from the harness without the clutch hooked up, with the A/C on. You should get 12V+. Hook the clutch line back up and meter the same line with the load of the clutch on it, A/C on, LPS jumped. Just get the meter probe into the disconnect with both lines attached. if you see a voltage drop, then it is caused most likely by the blue relay on the A/C controller in the console, bad freeze switch, or possibly a bad clutch depending on the resistance reading in the step above.
If you have a 12 volt power supply with at least a 3 amp capacity, (current sensing battery chargers will not work for this) or a motorcycle battery, you can disconnect the clutch wire form the harness and apply the 12 volts directly to the clutch and see if it engages. Be sure the clutch is isolated for the wiring harness.
When you say that the compressor will slowy cycle, are you saying that it turns slowly (like slipping)? or are you saying that it sometimes engages (on-off)? Do you hear a solid "click" when the clutch engages?
How oily is the area around the clutch and pully?
Greg
Measure the resistance of the clutch coil be unplugging the line going to it and use an ohm meter, measuring the line to the compressor to ground. I have to check on the proper resistance value, I have it written down somewhere, I'll look for it for you.
The next step is to check the voltage going to the compressor clutch. Jump the low pressure switch, Unhook the line mentioned above and check voltage on the line coming from the harness without the clutch hooked up, with the A/C on. You should get 12V+. Hook the clutch line back up and meter the same line with the load of the clutch on it, A/C on, LPS jumped. Just get the meter probe into the disconnect with both lines attached. if you see a voltage drop, then it is caused most likely by the blue relay on the A/C controller in the console, bad freeze switch, or possibly a bad clutch depending on the resistance reading in the step above.
If you have a 12 volt power supply with at least a 3 amp capacity, (current sensing battery chargers will not work for this) or a motorcycle battery, you can disconnect the clutch wire form the harness and apply the 12 volts directly to the clutch and see if it engages. Be sure the clutch is isolated for the wiring harness.
When you say that the compressor will slowy cycle, are you saying that it turns slowly (like slipping)? or are you saying that it sometimes engages (on-off)? Do you hear a solid "click" when the clutch engages?
How oily is the area around the clutch and pully?
Greg
08-06-2002, 04:44 PM
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Greg,
Thanks, I have all the equipment (12V power supply, etc.) needed to do that check.
When I say slowly cycles, I do mean turns slowly. Not so much like its slipping because there is no abreviated stutter. It will just turn slowly a couple times. That is even with low pressure on the high side and WITHOUT the pressure switch jumped to start the compressor. Like I said. It's acting weird.
Regards,
Thanks, I have all the equipment (12V power supply, etc.) needed to do that check.
When I say slowly cycles, I do mean turns slowly. Not so much like its slipping because there is no abreviated stutter. It will just turn slowly a couple times. That is even with low pressure on the high side and WITHOUT the pressure switch jumped to start the compressor. Like I said. It's acting weird.
Regards,
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08-06-2002, 05:29 PM
#8
The clutch should turn at either full speed, or not at all. There should be no in between. Try applying power directly to the clutch and see what happens. If it still just turns at the slow speed, the clutch is bad or not adjusted properly. If the clutch turns at full speed, there's a problem preventing enough current from getting to it. The relay in the climate control head unit would probably be a good possibility, but check everything between the clutch and control unit.
08-06-2002, 06:38 PM
#9
Three Wheelin'
Start with this:
Take a socket wrench and turn the compressor shaft on the front where the clutch is. It's like a 12mm or so nut. Turn only clockwise, it should turn freely. The belt and pully will not turn but the compressor shaft should. If you feel major resistence or rough, uneven turning, the compressor has issues. You need to do this to determine if the compressor is free to turn when the clutch engages.
Let me know please,
Greg
Take a socket wrench and turn the compressor shaft on the front where the clutch is. It's like a 12mm or so nut. Turn only clockwise, it should turn freely. The belt and pully will not turn but the compressor shaft should. If you feel major resistence or rough, uneven turning, the compressor has issues. You need to do this to determine if the compressor is free to turn when the clutch engages.
Let me know please,
Greg
08-06-2002, 06:59 PM
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John,
You have gotten some good advice (and I don't remember reading any outright bad advice) in the earlier posts.
A couple of suggestions to make the testing easier.
Make a four- or five-foot jumper wire. Turn the A/C on. Pull the harness from the low pressure switch on the side of the receiver/dryer. Crank the engine. Connect the jumper from the jump start terminal on the passenger fender well to one of the connectors in the switch harness, and see if the clutch engages and spins with the pulley. If not, connect to the other terminal in the harness.
If applying a good solid 12 vdc with good amperage available to one of the connectors on the low pressure switch harness makes the compressor clutch and compressor spin at full speed, the problem is probably the small relay in the controller, with a lower chance that it is the antifreeze switch of a wiring connector.
If the jumper makes the clutch work, and your jumper is long enough, you can hook the low pressure switch back up, and remove the black plastic shield at the base of the widshield. Hook the jumper from the jump start terminal to the electrical connector on the antifreeze switch that is closer to the firewall. If this makes the clutch work, the problem is probably the little relay.
If the relay is bad, you can replace the controller, replace the relay, or add an external relay.
You have gotten some good advice (and I don't remember reading any outright bad advice) in the earlier posts.
A couple of suggestions to make the testing easier.
Make a four- or five-foot jumper wire. Turn the A/C on. Pull the harness from the low pressure switch on the side of the receiver/dryer. Crank the engine. Connect the jumper from the jump start terminal on the passenger fender well to one of the connectors in the switch harness, and see if the clutch engages and spins with the pulley. If not, connect to the other terminal in the harness.
If applying a good solid 12 vdc with good amperage available to one of the connectors on the low pressure switch harness makes the compressor clutch and compressor spin at full speed, the problem is probably the small relay in the controller, with a lower chance that it is the antifreeze switch of a wiring connector.
If the jumper makes the clutch work, and your jumper is long enough, you can hook the low pressure switch back up, and remove the black plastic shield at the base of the widshield. Hook the jumper from the jump start terminal to the electrical connector on the antifreeze switch that is closer to the firewall. If this makes the clutch work, the problem is probably the little relay.
If the relay is bad, you can replace the controller, replace the relay, or add an external relay.
08-08-2002, 01:50 PM
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[quote]Originally posted by JE928Sx5:
<strong>Thank you Greg, Wally and Ed,
I'll give it a shot this weekend.
John</strong><hr></blockquote>
John -
I just went through some of this with my '88. Porsche want s abloody fortune for replacement A/C clutches and compressors, but thanks to our vendors we have some great alternatives. If the compressor checks out as being good, you can get a used A/C clutch from <a href="http://www.928intl.com" target="_blank">928 International</a> for $150 ($250 for '78/'79). And while Porsche wants something like $663 (w/GOOD core exchange) for a compressor & clutch alone, <a href="http://www.928gt.com" target="_blank">928 Specialists</a> carries the Griffith's kit (compressor, clutch and hoses - no core charge) for $535.
<strong>Thank you Greg, Wally and Ed,
I'll give it a shot this weekend.
John</strong><hr></blockquote>
John -
I just went through some of this with my '88. Porsche want s abloody fortune for replacement A/C clutches and compressors, but thanks to our vendors we have some great alternatives. If the compressor checks out as being good, you can get a used A/C clutch from <a href="http://www.928intl.com" target="_blank">928 International</a> for $150 ($250 for '78/'79). And while Porsche wants something like $663 (w/GOOD core exchange) for a compressor & clutch alone, <a href="http://www.928gt.com" target="_blank">928 Specialists</a> carries the Griffith's kit (compressor, clutch and hoses - no core charge) for $535.
08-08-2002, 05:08 PM
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Michael,
Thanks for the info. I am hoping that I don't have to go the route of a new compressor or clutch, but you are right that there are some good options. I have always been one that thinks if you are going to do it, spend the little bit extra to make it right. That's why I will never contemplate going with a Ford engine mount. Why use something that may work, when you have to put so much time and energy into doing it. In this case, the kit 928 Specialists has is probably the way to go if there is a compressor/clutch problem. Then you start the clock at Zero.
Regards,
Thanks for the info. I am hoping that I don't have to go the route of a new compressor or clutch, but you are right that there are some good options. I have always been one that thinks if you are going to do it, spend the little bit extra to make it right. That's why I will never contemplate going with a Ford engine mount. Why use something that may work, when you have to put so much time and energy into doing it. In this case, the kit 928 Specialists has is probably the way to go if there is a compressor/clutch problem. Then you start the clock at Zero.
Regards,
