I dont know how this is possible!!! (AC Compressor) - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 13 Old 05-06-2012, 05:13 PM Thread Starter
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I dont know how this is possible!!! (AC Compressor)

Ok, so I am working on a 01' Mustang GT, and the problem we are having is that the AC clutch is not activating. At first I related this to a bad coil (did not work straight wired) in the clutch, and due to the age of the compressor we decided to just replace everything. So after replacing the compressor and accumulator we started to test the system... Nothing... So we start troubleshooting mode, straight wired the clutch to the battery. The clutch enguaged!!! So we check power at the connector (after jumping the lowside switch) and we have 13.5VDC...

How is that posible????

After messing around with things for about an hour, we took our straight wire from the battery, and tried wiring it to the connector to the clutch. Thinking that the connections just were not making good contact... and nothing... Checked our connections with a multimeter and had 13.5VDC... Why is this not working????????

By the way we did successfully charge the system using the straight wire... So I only have to figure out this nightmare!

Thanks for any recomendations, and if you need any clarifications just let me know. I know this could be confusing...

Daniel


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post #2 of 13 Old 05-07-2012, 07:23 PM
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A couple things. First, are there any outstanding DTC codes? Are you aware that for many DTC's, the PCM will disable the AC by design.

Next, what did you do to confirm the AC clutch coil GROUND? For the 01 MY, the clutch is grounded via the CCRM. The wiring diagrams also show a diode inside the CCRM to reduce in-rush spikes. I could see a break (or bad CCRM) cause your reported symptoms.

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post #3 of 13 Old 05-08-2012, 10:33 AM Thread Starter
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I dont know that there are any DTC's but I will hook it up to my AE software tonight... Also, by checking the voltage at the connector between the black/yellow wire and black wire I had 13.5VDC. So that should verify my ground. I say that only because I was not grounding my meter to the chassis or anything, only the potetial difference between the two wires. This is what makes me confused...

Another person told me to check the air gap, but the compressor is tight, and honestly I would say a little too tight because it chattered when we first put it on. The noise went away after driving a few miles, but I definatley dont think I need to close the air gap any...

Thanks for the reply, and I will look into the software and check that. I think I might have a way of checking the CCRM as well... I will let you know if I find anything on there.
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post #4 of 13 Old 05-08-2012, 10:49 AM
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silly Q but is it out on low pressure??


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post #5 of 13 Old 05-08-2012, 03:05 PM
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Quote:
Originally Posted by redpony01 View Post
silly Q but is it out on low pressure??
x2

Another silly question, on sn95 cars we have a cycle switch that is known to go bad, if the switch is bad it does not activate the clutch; does your car have this? To bypass the cycle switch and have the ac on all the time, just run a jumper wire inside the connector.
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post #6 of 13 Old 05-08-2012, 11:02 PM
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Originally Posted by 94OrangeStangGT View Post
I dont know that there are any DTC's but I will hook it up to my AE software tonight... Also, by checking the voltage at the connector between the black/yellow wire and black wire I had 13.5VDC. So that should verify my ground. I say that only because I was not grounding my meter to the chassis or anything, only the potetial difference between the two wires. This is what makes me confused...

Another person told me to check the air gap, but the compressor is tight, and honestly I would say a little too tight because it chattered when we first put it on. The noise went away after driving a few miles, but I definatley dont think I need to close the air gap any...

Thanks for the reply, and I will look into the software and check that. I think I might have a way of checking the CCRM as well... I will let you know if I find anything on there.
OK, now that I know how you did the voltage measurements, we can work on some new theories.

You stated that the clutch engaged when ran straight from battery. How did you do this? In other words, did you run just a positive wire (thus using the built in ground)? Or did you run a positive and negative?

What's the the clutch voltage when the clutch is engaged? Consider the possibility of a high resistance connection. When current begins to flow, the voltage will drop due to the resistance. This could create a case where there isn't enough voltage to "pull in" the clutch coil.

If it is a high resistance connection, the next trick is to locate where. My vote is to start at the CCRM. Very first thing is to inspect the CCRM connector for evidence of overheating or water damage.

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post #7 of 13 Old 05-09-2012, 04:49 PM
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Test ohms on the harness ground wire to battery ground, if it's not near zero chase it and figure out why.

If that's good I would make some jumper wires with male/female spade terminals on either end to go between the factory harness and the spades on the compressor. Thing with Ford harnesses is that you can't tell if you've got a good connection in the plug or not.

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post #8 of 13 Old 05-09-2012, 08:34 PM Thread Starter
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silly Q but is it out on low pressure??
It was out of freon, but after charging the system I hooked it al back up n got nothin... I know the low pressure switch and high pressure switch is working because I am getting voltage at the compressor

Quote:
Originally Posted by orl1mjf View Post
x2

Another silly question, on sn95 cars we have a cycle switch that is known to go bad, if the switch is bad it does not activate the clutch; does your car have this? To bypass the cycle switch and have the ac on all the time, just run a jumper wire inside the connector.
I am working on an 01' and I am 99% sure the switches are working because even with jumpers I get the same result. 13.5vdc at the compressor...

Thank you all for your thoughts! Please keep em comin!!!


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post #9 of 13 Old 05-09-2012, 08:42 PM Thread Starter
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OK, now that I know how you did the voltage measurements, we can work on some new theories.

You stated that the clutch engaged when ran straight from battery. How did you do this? In other words, did you run just a positive wire (thus using the built in ground)? Or did you run a positive and negative?

I ran both positive and negative...

What's the the clutch voltage when the clutch is engaged? Consider the possibility of a high resistance connection. When current begins to flow, the voltage will drop due to the resistance. This could create a case where there isn't enough voltage to "pull in" the clutch coil.

How can I check this? Maybe disconnect ground and measure current? I went through some elec theory classes but it's been a while!

If it is a high resistance connection, the next trick is to locate where. My vote is to start at the CCRM. Very first thing is to inspect the CCRM connector for evidence of overheating or water damage.
This all makes some since to me and I think you could be on to something... How do you think I can begin troubleshooting this??? If you cannot see my responses (not sure if they show up in bold) I replied in the above quote...

Thanks again guys!!! I don't think any of my vehicles would be running without the help of forums!


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post #10 of 13 Old 05-10-2012, 02:33 PM
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Quote:
Originally Posted by 94OrangeStangGT View Post
This all makes some since to me and I think you could be on to something... How do you think I can begin troubleshooting this???
Already mentioned one method to trouble shoot this. Measure the voltage at the clutch coil with everything hooked up when the clutch is engaged. If there is a high resistance connection, the voltage will drop well below the normal battery voltage. Use a known good ground for the testing. Note, it's normal for the voltage to drop some. What we are looking for is a huge drop.

It has already been mentioned to measure the resistance back to battery negative. Remember to isolate the clutch coil before doing any Ohm readings. Also, if you shoot back through the clutch coil towards ground, this will pick up the resistance of the coil and may lead to the wrong conclusion.

Have you confirmed that the battery cables are clean and tight? What about the battery negative? They are bad about splitting. What about the grounds around the radiator core support? Are they clean and tight?


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post #11 of 13 Old 05-11-2012, 10:25 PM Thread Starter
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Thanks for the help guys, with your help I think I have isolated it to the CCRM... Gonna try to locate one and replace it tomorrow. I will keep y'all posted!


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post #12 of 13 Old 05-16-2012, 10:14 AM
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Here's some information on a Reman unit. Check out the compatibility tab in case you want to go the salvage yard route.

Cardone Remanufactured 73-70013 - Body Control Computer | O'Reilly Auto Parts
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post #13 of 13 Old 05-26-2012, 12:07 PM Thread Starter
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Well I ended up getting one out of Cali somewhere, but it was the CCRM. Thanks for the help guys, and sorry I didn't update this sooner!


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