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2001 Chevrolet Monte Carlo AIR CONDITIONING

Tiny
BEALE120
  • MEMBER
  • 2001 CHEVROLET MONTE CARLO
  • 3.8L
  • V6
  • FWD
  • AUTOMATIC
  • 5,000 MILES
Hello 2 Car Pros,

I have an 01 Monte Carlo SS with 5000 miles and the AC does not work.

I don't suspect anything with refrigerant pressure based off the mileage of the car. For some reason the relay will not close when the car is running (I did change the relay nothing changed). I don't have power but I do have ground from the body ground at the AC Compressor connector. The only way I get power is by manually closing the relay's contact points, then the compressor runs. All other fuses in the diagram are powered as well. Also the relay control at the PCM is closed (Grounded) as well. I would say all the parameters are met on the pressure side of the PCM to close the clutch relay control ground.

Am I fooled by the PCM, or something else? I really want to thank you for your time and help. I really appreciate it!

Eric
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Tuesday, April 15th, 2014 AT 11:12 AM

14 Replies

Tiny
WRENCHTECH
  • MECHANIC
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Everything start with gauges and checking the pressures to make sure you have sufficient refrigerant for the compressor to engage. If you have 60 to 70 pounds of static pressure, then you have to look at the electrical circuit by following a wiring diagram. You can test the relay sock for correct signals using a test light that reads both power or ground. You should find 2 sockets reading power and 2 sockets reading ground when the AC is on.
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Tuesday, April 15th, 2014 AT 12:45 PM
Tiny
BEALE120
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I appreciate your quick response, do you think that pressure might be a factor?

The way I interpreted the system as for the PCM is that once the pressure side has the certain amount of pressure the PCM will send the signal to the relay control and close the contact to supply ground to the relay coil. The relay contact point I have tested is grounded by the PCM. Since the relay control at the PCM is grounded it's telling me that the system is pressurized and has met the standards to close the relay control for ground. Since I have that I still don't understand why my AC Clutch relay is not closing. Have you ever heard of this problem?

Thanks Eric
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Tuesday, April 15th, 2014 AT 1:40 PM
Tiny
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Are you sure about that? Check all sockets. You should find 2 that are powered and 2 that read ground, one being the trigger from the PCM and the other being the clutch itself. Pull the relay in and out and see if you feel it clicking. If it's not clicking, then you have to find out what is wrong with the signals or the relay itself. If the relay is clicking, then remove it and try jumping out the sockets for pin 30 and pin 87. These should be at diagonal corners.
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Tuesday, April 15th, 2014 AT 3:02 PM
Tiny
BEALE120
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When in the running position I have probed on relay control side pin 85 (PCM GROUND) and 86 (FUSED POWER)there is power and ground there. Load side of relay pin 30 has power but never touches pin 87, unless I press it with my finger. That why I replace the AC relay I thought something was wrong with the coil inside the relay. The fact that the AC clutch relay control at the PCM is grounding my relay rules out any pressure problems. If it wasn't grounding my AC relay then it would be on the pressure side.

Does this make sense? Do you think the new relay I have is wrong, the internals are a bit different from the original? I'm not sure what else it can be.
Thanks Eric
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Tuesday, April 15th, 2014 AT 4:06 PM
Tiny
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There has to be something wrong with your testing. You have all the components for the relay to energize. If you are using an LED test light, they can fool you sometimes. They will illuminate with even the slightest of signals. If you can get at the bottom of the relay box and try to manually ground that trigger wire on pin 85 to see if anything changes. Make sure you're actually dealing with the correct relay also. Did you try jumping the sockets for pins 87 and 30? Did the compressor come on?
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Tuesday, April 15th, 2014 AT 4:17 PM
Tiny
BEALE120
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In my testing I use a Greenlee Multimeter I don't use a LED test light. I did use a piece of wire at pins 30 and 87 it sends power to my AC Clutch connector. When I start it, it blows my AC Compressor fuse. I have only done it once but didn't think that it would be a problem, or could it? If I have the relay in place and press it with my finger compressor runs no fuses blow. Can the internal design of the relay be a problem, my original is different from the aftermarket relay (Not really sure)?

Any ideas Eric
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Tuesday, April 15th, 2014 AT 4:33 PM
Tiny
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That just doesn't add up at all. Jumping those 2 pins does the exact same thing as the relay does when it energizes. The same fuse powers the same circuit. Are you sure you have the right pins. Not much of what you are saying is adding up.
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Tuesday, April 15th, 2014 AT 4:38 PM
Tiny
BEALE120
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It really doesn't make sense. And the relay is not put in the wrong direction either. When I bypass the relay with wire at pin 30 and 87 it burns a fuse? Then I put the relay in and hold it, it sends power to connector and compressor but doesn't burn any fuses. Yes it is the same thing. I'll continue to make sure that I'm testing the right pins and I'll get back with you on the turnout.

Do you have the ECM pinout diagram and ECM wiring diagram for a 93 Ford 3.8 V6 Supercharged? The Autozone diagrams don't add up.
I really appreciate your time and help!
Thanks
Eric
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Tuesday, April 15th, 2014 AT 6:10 PM
Tiny
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It doesn't matter which way the relay is plugged in. 30 and 87 are at diagonal corners so it works either way but if you are jumping the trigger power instead of the supply power, you will blow a fuse and if you are jumping that to the computer trigger, you will burn out the quad drivers in the computer. You have to be doing something wrong.

As far as the other car, that has nothing to do with this question so you need to post that in a new question.
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Tuesday, April 15th, 2014 AT 6:18 PM
Tiny
BEALE120
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I have never bypassed anything other than pins 30 and 87. Never bypassed anything else. I never power jumped anything either (too dangerous everything is sensitive). Everything else was just testing for power and ground. I'll let you know when I figure it out. I'll also make a new post for my Thunderbird.

Thanks bud

Eric
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Tuesday, April 15th, 2014 AT 6:57 PM
Tiny
BEALE120
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Hey Bud,

I though I would get back with you on the AC problem I'm having. I got around today to do more testing and found that the PCM wasn't grounding the coil side of the AC clutch relay. I did the test with the relay in place. I wrapped a piece of stranded wire around each pin of the relay and found that the PCM wasn't grounding the relay. So I must be something on the pressure side like you said. I was fooled by the computer! LOL!

Eric
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Wednesday, April 16th, 2014 AT 5:54 PM
Tiny
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Yep, this is where you need a scan tool with data capability. This system uses a single, 3 wire pressure sensor that send the specific pressure to the PCM and the PCM act accordingly with the compressor clutch and fans. You need to see what pressure the computer is seeing.
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Wednesday, April 16th, 2014 AT 6:00 PM
Tiny
BEALE120
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I really want to thank you for all of your expertise. I feel like a fool about the grounding problem. I should start listening to my elders (I'm 23 years old). LOL Thanks for your time and effort on this, I can take it from here. Thanks bud!

Eric
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Wednesday, April 16th, 2014 AT 6:24 PM
Tiny
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You're welcome
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Wednesday, April 16th, 2014 AT 6:29 PM

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