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A/C Clutch spins only when jumped

Tiny
ARMYDOC82
  • MEMBER
  • 2002 PONTIAC BONNEVILLE
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
Okay so, I had to replace my condenser. A/C hasn't worked since the end of last summer simply because I haven't felt like fooling with it until now, to be honest. Well, I got it in today and got everything tight and right. I went to charge the system with a DIY can of A/C PRO, and the clutch absolutely would not spring to life. So, I swapped out relays to see if that may be the problem and it still didn't work. I ended up making a little jump wire and got the clutch to work, but that is the only way it will work. So, my question is, what is not commanding the clutch to come on? Is it a pressure switch? Or is it something in the ECM or BCM not commanding it on? I seriously have to get the A/C working in this car, it's my wife's car and my 4-year-old daughter has to ride in it sometimes and our heat index has been 110 the last 3 days in a row! Please help!
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Friday, June 17th, 2022 AT 6:37 PM

9 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
This could be a couple of things but let's start with how it works.

If you look at the wiring diagram, the relay is powered on pin 30 and 86. So we need to make sure you have 12 volts on both wires when you have the key in the on position.

Next when the A/C is supposed to be on, the PCM grounds the relay by applying ground to pin 85 which energizes the relay and closes the contact inside. This will then complete the circuit from pin 30 to 87 which sends power to the compressor.

So, what I would do is check the power on 30 and 86. Then check the ground on pin 85. You do this by putting your red meter lead on a 12-volt source like the battery. Then put the black lead on terminal 85 and turn the key on and AC on. Your meter should read 12 volts.

https://www.2carpros.com/articles/how-to-check-wiring

If it is not, then the PCM is not commanding the relay on.

At that point, it could be a PCM issue, but it could also be a pressure issue or a pressure sensor issue. So that means we need to check and see what the actual pressure is in the system.

https://www.2carpros.com/articles/re-charge-an-air-conditioner-system

If the pressure is not correct when you jump the relay to get the compressor to come on, then we need to set the pressure correctly and see if the compressor will come on.

If it still does not, then we have a sensor or PCM issue.

So, let's start with all this info and then if we get there, we can figure out if we have a sensor or PCM issue.
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Saturday, June 18th, 2022 AT 7:55 AM
Tiny
ARMYDOC82
  • MEMBER
  • 5 POSTS
Thank you very much! As soon as I get done with the customer car, I'm working on now I'll check all of that out and get back to you.
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Saturday, June 18th, 2022 AT 11:10 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Sounds great. Let me know if you have questions but just make sure when checking that terminal of the relay from the PCM that you are checking for ground.

It is a little confusing but if we are not checking for ground on that circuit then we will go down a rabbit hole as it gets frustrating as everything seems to check out okay.
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Saturday, June 18th, 2022 AT 1:19 PM
Tiny
ARMYDOC82
  • MEMBER
  • 5 POSTS
Hey Kenny, okay so, I'm getting perfect voltage on 30 and 86 just like I'm supposed to. Unfortunately, I'm getting absolutely nothing on 85. I was going to check the plug pins on the high-pressure sensor, but I can't find it. The only place I couldn't see was the back of the compressor itself. My car has the 3800series 2. Now, on the 3800 series 3, the sensor is right below the air intake box, but it certainly is not on the series 2. By the way, I very much appreciate all the help/tips/tricks!
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Saturday, June 18th, 2022 AT 8:25 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
Okay. Just want to make sure you checked 85 the opposite way you checked 30 and 86. Meaning you check 85 for a ground so you put your meter on 12 volts and then the black lead on 85 and turned the AC on? If you did and have nothing, then the PCM is not grounding it.

I am attaching the location and replacement for the sensor. It is located behind the compressor on an A/C line.

This is a 3-wire sensor so we are not able to jump it to see if the compressor will come on. So, we need to check the pressure and see if the pressure is correct. If it is, then the sensor would be the likely cause.
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Sunday, June 19th, 2022 AT 7:07 AM
Tiny
ARMYDOC82
  • MEMBER
  • 5 POSTS
Yes, I checked the 85 opposite the way I checked 30 and 86. I was also able to get my hands on a PCM pinout as well, just in case. Oh, and I have already checked the pressure while I had the compressor jumped and clutch running. It was perfect. I'll get the sensor replaced and let you know what happens. Again, and as always, thank you very much Kenny!
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Sunday, June 19th, 2022 AT 1:49 PM
Tiny
KASEKENNY
  • MECHANIC
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Sounds like a great plan and that is probably exactly what I would do.

Keep us posted on what you find. Thanks
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Sunday, June 19th, 2022 AT 5:57 PM
Tiny
ARMYDOC82
  • MEMBER
  • 5 POSTS
Hey Kenny! Sorry it's been so long but I had a medical issue. I was in the Army for 12 years and during my third tour in the war I started having seizures. Still have them to this day and that's the reason I'm just getting around to responding. Anyway, the old girl is blowing icy cold air now bud! I ended up having to get new (salvage yard new) A/C lines. My entire problem started life with a leak in those said lines. I got new ones from Advance zone Oreilly and didn't pay close enough attention. There was no pressure switch on them, only a relief valve. I looked everywhere for brand new ones that were correct but apparently, they don't exist. Anyway, took a stroll through my favorite salvage yard and he had plenty of them! Again, thank you so much for everything bud! Take care. Jacob
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Friday, July 1st, 2022 AT 8:29 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,895 POSTS
KENNY K is one of our best, Use 2CarPros anytime, we are here to help. Please tell a friend.
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Monday, July 4th, 2022 AT 12:01 PM

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