No Power To AC Clutch (THIS IS A TOUGH 1)

[bigdog225]

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Im at a total loss here and in desperate need of some electrical help on my 96 Mustang Cobra.

Cannot get power to the Ac compressor

I have power at the Fuse, Blower, Low Pressure Switch, High Pressure Switch, and have replaced the CCRM thinking that was the culprit. Still no power to the plug at the compressor clutch.

A little history, new compressor, ac lines, evaporator, drier, high and low pressure switch and now ccrm.

Flushed system, held vaccum, filled with 34oz r134a. after running ac and blowing cold i noticed my temp rising and voltage dropping on and off. High speed fan seemed to kick on a little later then I would have liked but didnt near over heating and was still in the normal range and held fine.

After shutting car down approx 30 mins later ac line blew that connects to the evaporator at the firewall. Replaced the line, replaced alternator since battery checked out fine, and replaced coolant temperature sensor. flushed system, vaccumed and went to charge and no power at compressor clutch.

Jumping it at low pressure switch doesnt work either. Direct wired up compressor and filled with r134a again and oil. Blows cold and no blowing of the line however need to figure out why im not getting power to compressor clutch...

Going on week two of this craziness and at this point out of ideas.

 

[wmburns]

Confirm fuse I/P 10 (15a).

Any other damage to nearby wiring harness?

Are there any other DTC's? Especially any related the IMRC's? Have you done an IMRC delete?

Confirm there is +12 volts at CCRM pin#23 (BK/Y) with the engine running and AC on.

If not, STOP and find out why.

Ground CCRM pin#16 (BK) to a known good ground. Does the AC clutch engage now?

Confirm the CCRM ground. With the key off, measure the resistance of the CCRM pin#15(BK/W) wire back to battery negative. Should be low. Post.

 

[bigdog225]

Confirm fuse I/P 10 (15a).

Any other damage to nearby wiring harness?

Are there any other DTC's? Especially any related the IMRC's? Have you done an IMRC delete?

Confirm there is +12 volts at CCRM pin#23 (BK/Y) with the engine running and AC on.

If not, STOP and find out why.

Ground CCRM pin#16 (BK) to a known good ground. Does the AC clutch engage now?

Confirm the CCRM ground. With the key off, measure the resistance of the CCRM pin#15(BK/W) wire back to battery negative. Should be low. Post.

Thanks for the response. I feel we are making headway already. Ive had a sys lean / rich code for awhile that I thought was due to a hole in the exhaust. But since you mentioned it I had someone run out and see if there was any new codes and yes there is now a code of P1519 IMRC stuck closed.

Havent had a chance yest to check the other things but could this closed IMRC be the culprit? Im not sure if its been deleted. Im guessing not since ive never had that code before and now i do...???

Any and all guidance is extremely appreciated.

 

[wmburns]

The grounds for the AC clutch go through the IMRC control. I'm not sure why but if asked to guess, it's a method to disable the AC clutch when the motor load is heavy.

So it seems reasonable to me that an IRMC failure could have an effect on the AC clutch. The trick now is to determine if this is a wiring fault caused by the rupture or something unrelated. The sequence of events will be important.

I take it you are not the one doing the work.

 

[bigdog225]

The grounds for the AC clutch go through the IMRC control. I'm not sure why but if asked to guess, it's a method to disable the AC clutch when the motor load is heavy.

So it seems reasonable to me that an IRMC failure could have an effect on the AC clutch. The trick now is to determine if this is a wiring fault caused by the rupture or something unrelated. The sequence of events will be important.

I take it you are not the one doing the work.

My buddy has a shop and is doing the work. Im relaying all this info to him. While I was awaiting your reply I found a pdf of how to remove and clean the IMRC. So what would you suggest we do next? Is it possible that the issue of the speratic voltage drop, ac clutch power all be tied into the IRMC cleaning? Is the fix for the IRMC just pulling it out and cleaning it? Or is there an electrical component that needs to be replaced there? Thanks again for your help.

 

[wmburns]

Already told you what my suggestions are.

I doubt a dirty IMRC is causing this. Seems Electrical to me. Perform the tests and go where they take you. Much better than guessing.

 

[bigdog225]

Will do. Thanks again

 

[bigdog225]

Confirm fuse I/P 10 (15a).

Any other damage to nearby wiring harness?

Are there any other DTC's? Especially any related the IMRC's? Have you done an IMRC delete?

Confirm there is +12 volts at CCRM pin#23 (BK/Y) with the engine running and AC on.

If not, STOP and find out why.

Ground CCRM pin#16 (BK) to a known good ground. Does the AC clutch engage now?

Confirm the CCRM ground. With the key off, measure the resistance of the CCRM pin#15(BK/W) wire back to battery negative. Should be low. Post.

Pin#23 (BK/Y) with the engine on and ac on flashes between 0.01 and 0.00 repeatedly. If I add 12v there compressor kicks on.

Grounded CCRM pin # 16 to good ground still no clutch engage. With engine on reads the same as Pin 23. Flashes between 0.01 and 0.00 repeatedly.

With the key off, resistance of the CCRM pin#15(BK/W) wire back to battery negative reads 0.01

Any help is appreciated.

 

[wmburns]

Pin#23 (BK/Y) with the engine on and ac on flashes between 0.01 and 0.00 repeatedly. If I add 12v there compressor kicks on

We are getting closer now. CCRM pin#23 is the output to the clutch coil. No voltage=no clutch.

With the key on and AC on, test for +12 volts at CCRM pin #21 (DG/O).

If voltage, likely a bad CCRM or there is still a wiring fault to hone in on or the PCM is flat not calling for AC. What is the voltage on CCRM pin#22 (PK/Y)? What happens when pin#22 is grounded? Does the clutch engage?

If no voltage, there is a problem in the wiring, fuse, AC high pressure switch, AC cycling switch, or control panel. Retest to confirm there is voltage at these control points.

 

[bigdog225]

We are getting closer now. CCRM pin#23 is the output to the clutch coil. No voltage=no clutch.

With the key on and AC on, test for +12 volts at CCRM pin #21 (DG/O).

If voltage, likely a bad CCRM or there is still a wiring fault to hone in on or the PCM is flat not calling for AC. What is the voltage on CCRM pin#22 (PK/Y)? What happens when pin#22 is grounded? Does the clutch engage?

If no voltage, there is a problem in the wiring, fuse, AC high pressure switch, AC cycling switch, or control panel. Retest to confirm there is voltage at these control points.

Im not at the car at the moment but I did test some of these last night.

With car running and ac on pin #21 had power. Didnt test it with just key and ac. Pin # 22 had no power with car running and AC on. Was affraid to ground or send 12v to pin 22 as I didnt know what it was supposed to be doing and didnt wanna toast any components.

Rechecked fuse, cycling switch, and high pressure switch. All tested good. Purchased a reman ccrm several days ago and it didnt help.

I have not pulled the control panel inside as I thought the order in which the voltage traveled to power the ac clutch was fuse, control panel, cycling switch, high pressure switch, ccrm. Ill pull the control panel today. Can you tell me what wires there should be doing.

Let me know your thoughts on the other tests I did and if I need to do others.
Thanks again this has been a nightmare

 

[wmburns]

My suggestion. Use an ODB2 scanner to find out if the PCM is actually calling for AC. If the PCM is NOT calling for AC, this would explain why the clutch is not engaging. Then it's a matter of finding out why.

CCRM Pin#22 is the PCM control circuit. In the diagrams, it's not clear if this is a ground start or a voltage sense circuit. Since the CCRM is new, let's assume the CCRM is good. Then if there is no voltage at CCRM pin#22, this implies it's a voltage sense circuit.

IF injecting +12 volts to Pin#22 makes the clutch engage, this says that the CCRM is working. Therefore either the PCM is bad or there is a break in the PK/Y wire back to PCM pin#69.

 

[bigdog225]

My suggestion. Use an ODB2 scanner to find out if the PCM is actually calling for AC. If the PCM is NOT calling for AC, this would explain why the clutch is not engaging. Then it's a matter of finding out why.

CCRM Pin#22 is the PCM control circuit. In the diagrams, it's not clear if this is a ground start or a voltage sense circuit. Since the CCRM is new, let's assume the CCRM is good. Then if there is no voltage at CCRM pin#22, this implies it's a voltage sense circuit.

IF injecting +12 volts to Pin#22 makes the clutch engage, this says that the CCRM is working. Therefore either the PCM is bad or there is a break in the PK/Y wire back to PCM pin#69.

Had a second to run and take a look but couldnt find the odb2 scanner so I will check for that after work. I did however check pin # 22 and it read 0.01 with car on and ac on. Applied 12v and compressor kicked on.

 

[bigdog225]

Had a second to run and take a look but couldnt find the odb2 scanner so I will check for that after work. I did however check pin # 22 and it read 0.01 with car on and ac on. Applied 12v and compressor kicked on.

Tried to read the data from obd2 to see if AC was getting ON signal from PCM but couldnt because of the error code P0117 regarding coolant temp sensor. When I changed out the coolant temp sensor the pigtail broke and apparently the way I have whats left of the pigtail plugged in is not suffcient enough to the cars likeing. I am trying to chase down that pigtail now. Very hard to find. Does this connection have anything to do with the AC getting signal to come on?

 

[wmburns]

It's possible that the PCM disables the compressor as part of the "failure effects mode". Not sure. Also possible there is a break in the contol wiring as has been mentioned. May just have to pull the PCM and ring out that circuit. Then you will know for sure.

Still would be handy to know if the PCM is calling for AC.

 

[bigdog225]

I am happy to report this thread can now be closed out. My car is now blowing ice cold again thankfully. Below I will explain my findings as this thread could be good for someone tracing all the electrical possibilities to the AC clutch in our cars.

As mentioned above I had replaced the alternator and coolant temperature sensor during the install of an ac line and broke the pigtail to the coolant temperature sensor in the process but enough of it was left to plug in. Here is where it all went down hill. Oreilly whom I always prefer over autozone sold me a coolant temperature sensor Motorcraft part number SW5110.

After installing and plugging in what was left of the pigtail I moved on. However after going through all of the craziness documented above trying to find out why no power to the AC clutch I decided to order that pigtail thinking it may be the culprit because of the CEL P0117. Order it from ford (special order part # WPT-989).

Upon trying to plug the new pigtail in it didnt fit. Turns out Oreilly sold me a Coolant Temperature Switch instead of a Sensor. They look the same but the track for the pigtail is a little different. As I wasn trying to figure out if Ford sold me the wrong pigtail or Oreilly sold me the wrong sensor. I went to Oreillys website and looked up Coolant Temperature Switch for Motorcraft and noticed they had the same part number as they had for the sensor (SW5110).

Went to autozone, got the coolant temperature sensor, put everything together and AC kicked right on....

In conclusion...
If I had the right sensor to begin with the broken pigtail I had left would have been fine or if I hadnt broke the plastic around the pigtail it wouldnt have fit into the wrong part I was sold and would have known I was sold the wrong part and this wild chase would have never happened. Im sure there are others out there with this broken pigtail as it was pretty hard to find and took the dealer a while to locate.

Another important lesson learned is the coolant temperature sensor is a part of the circuit for the AC even though I could not find that in any of the diagrams.

WMBURNS thanks for all your troubleshooting help. This nightmare did result in a lot of new and useful knowledge for me on my car regarding the wiring, IMRC, CCRM, etc. Also through all of this I believe I now know why I have had a lean code come and go as the IMRC probobly needs a real good cleaning.

Thanks again

 

[trombonedemon]

:grouphug:

 

[wmburns]

To anybody reading this post, this is an example of why it's important to list all of the symptoms and DTC codes present on your car. Today's computer controlled cars are sometimes smarter than we may want to give them credit for. Here is an example of "failure mode effects" in action. IE, the PCM taking action to limit the effects of other failures. In this case, because the PCM does not know the temperature of the motor, it disables the AC to limit the motor's heat production.

This is also an example of how an ODB2 scanner could have saved a ton of time. The OP could have checked the AC clutch PID and seen right away that the PCM was not even calling for AC. Armed with that knowledge, no time would have been spent replacing and trouble shooting parts that control the AC clutch.

IMO, a dirty IMRC is not going to cause a lean DTC. There is some other reason for the lean DTC.