A/C Issue

[Silver Fox]

My a/c decided to stop blowing cold air. The compressor clutch is not engaging even when jumping the low pressure switch.

The system was converted to R-134 in 1999 according to the sticker on the a/c system. I bought the car in 2005 with no issues with the a/c until 2010, when the low pressure switch gave out. If I recall we added about one half pound of R-134 when I replaced the switch. It held vacuum when we added the freon.

I can find three electrical plugs on or near the compressor - they are all plugged in and tight (one on an aluminum line (going to the compressor) with three wires, one in the rear of the compressor with two wires, and one of the front bottom of the compressor near the clutch with two wires on it).

The 25 amp fuse in the car for the a/c is good (ohmed it out to be sure).

The cooling fan does not kick on when I turn the a/c on (but the car was not fully warmed up either when I tested it).

The last time I used the a/c it worked great on a 100 degree day. The only thing I have done to the car since then is changed the motor mounts and took the valve covers and plenum off to have them powdercoated. I don't see how either of these could have any bearing on the a/c though, unless I may have accidently disconnected something.

Any tips on what to try next?

I thought about attaching some jumper wires from the battery to the compressor clutch (which I take it is the plug in the front), but cannot really figure out how to connect power/attach alligator clips to the connectors due to the location of the connectors.

Or do I need to have it hooked up to some pressure gauges to see if perhaps my R-134 leaked out?

I'm hoping someone can point me in the right direction, as electrical and a/c issues are both areas I can stand to improve in.

Rob

 

[Scott Atk]

If you have a meter or test light, check the low pressure switch that you jumped. Should have 12V on one side.

 

[jopaustu]

Search "ac wiring diagram". There is a post from july 10 2012 from QUIP'6' along the lines of your post. I think charlief1 provided a schematic of the circuit,and others had some good input that may help

 

[Silver Fox]

Scott - I have 12.62 volts on one side of the low pressure switch with the a/c on, something like 0.001 to 0.02 volts with the a/c off.

Jopaustu - I have a factory service manual with the diagram. I had searched but didn't find that thread from Quip 6. That was an interesting read and sounds similar to my issue. It gives me a few more things to check.

 

[Silver Fox]

After some more troubleshooting today, I:

- reconfirmed the voltage to the low pressure switch,

- put power to the clutch and discovered it does engage when energized,

- discovered the green wire going to the compressor clutch is not energizing.

Per the wiring diagram, I am going to run a continuity check on the green wire from the compressor switch back to the relay and see if I have a break in the wire.

Is there any way to test the relay other than switching it out?

Rob

 

[Silver Fox]

Troubleshooting round 2:

Green wire has continuity from the a/c relay plug to the compressor clutch plug (using ohm meter).

The blue wire going to the a/c relay has power (tested via a test light) when the a/c is turned on, no power with a/c turned off.

As am not getting power via the green line coming from the a/c relay to the compressor clutch (although their is power going to the a/c relay), should I replace the relay?

Or could it be another problem (high pressure switch, system totally discharged, etc)?

Thanks,

Rob

 

[charlief1]

You may have a realy you can swap out for the bad one Rob, or you may be able to take the relay apart and check it internally. I've done that many times myself so I could check the contact in them.

 

[Scott Atk]

Sounds like the relay to me.

 

[Silver Fox]

Charlie and Scott,

New relay installed and no change. Still no power through the green wire going to the compressor clutch.

Any more tips, before I throw in the towel and take it to a mechanic?
- Could the high pressure switch be a possible cause?
- How would I "jump" this to see if it makes a difference?

Rob

 

[charlief1]

The high pressure switch is on the back side of the power so you should be able to just ground it to see if power goes through.

On the relay we know you're getting power to it for the clutch, but it's not getting there. Are you getting a signal to turn it on?

 

[Silver Fox]

The high pressure switch is on the back side of the power so you should be able to just ground it to see if power goes through.

On the relay we know you're getting power to it for the clutch, but it's not getting there. Are you getting a signal to turn it on?

Charlie,

I took the car to a local shop, and paid an hours worth of labor to be not much further ahead. They:

- Evacuated the system and it was about one-half pound low which they added.

- They hooked up a Snap On scan tool to see if the ECM is getting an A/C "on request" when the A/C is turned on - the scanner indicated the ECM was not getting an A/C on signal (yes/no field on the tool - showed no).

- Three people at the shop looked at the relay, and think the plug going into the relay "might" be bad, and want to rule that out. The pigtail is "gunked" up with a tar like substance and looks pretty old/used. The boss man's theory is that although I am getting 12 volts from the ECM (into the plug) it might not be returning the signal back to the ECM (per the wiring diagram) because of a bad plug. They said they could get me a replacement relay pigtail for $80.00; I told the I would get one from Caspers for $8.95. They want to rule this out as the problem before trouble shooting any further.

I think I will get the pigtail and splice it in myself to see if it makes a difference.

After some additional troubleshooting by myself, I have discovered:

- The radiator cooling fan does NOT come on when I turn the A/C on.

- If I disconnect the A/C pressure line switch with three prongs (on the A/C line, driver's side, behind the alternator) and ground two of the three wires the radiator fan comes on (one prong turns the fan on low speed, where the other prong turns the fan on high speed, and the third prong appears to be a ground).

Based on the new information and the thoughts of the mechanics, what are you thinking?

This is frustrating. At least I know the system is not discharged now.

Rob

 

[Silver Fox]

It's fixed, and I wouldn't have figured it out if I hadn't gone to the shop earlier today. The boss man there thought the relay plug was bad and sensed the pink/black wire was not communicating with the ECM. He was right.

I went to Vortex Buicks and pulled up ECM wiring diagram (www.vortexbuicks-etc.com/ecmwiring.htm) and at the very bottom of the page it shows the pink /black wire going to the ECM/ERLS fuse (10A). I went to the car, and pulled the a/c fuse again as well as the ECM/IGN (10 amp) fuse. Both looked good and ohmed out good.

Further frustrated, I came back to the computer and did some more searching and ended back on Vortex Buicks and found a fuse panel diagram with explanations (http://www.vortexbuicks-etc.com/fuse_block.htm) and noticed this wording:

"ECM/SOL - Brake switch, wastegate solenoid, canister purge solenoid, coolant fan delay relay, Electronic vacuum regulator valve, A/C cutout relay. Powered by pink/black wires."

When I saw the "A/C Cutout Relay" and "Powered by pink/black wires" I became hopeful.

I went out and pulled the ECM/SOL fuse and sure enough, it was blown. I plugged a new one in, fired the car up, turned on the A/C, to be greeted by nice cold air blowing from the vents.

Morale of this story: If your A/C stops working and you cannot for the life of you figure out why it isn't working when everything appears to be okay, check the A/C fuse (25 amp) and the ECM/SOL fuse (10 amp).

Now I just have to wonder why the fuse blew.

Thanks for everyone's help, and I hope this solution will help somebody out in the future.

 

[charlief1]

Glad you got it done Rob. If you need anymore help either PM or call me.

 

[Pronto]

Good catch. I hate electrical issues.

 

[VIN7]

Look at the compressor plug near the clutch/pulley. There is a stiff, bare wire that looks like a resistor. If that wire grounds out it will blow that fuse. I wrap that with electrical tape.

 

[Silver Fox]

Look at the compressor plug near the clutch/pulley. There is a stiff, bare wire that looks like a resistor. If that wire grounds out it will blow that fuse. I wrap that with electrical tape.

Thanks Mike. I electrical taped it after reading your post.

Rob

 

[Joeld]

This is a great thread, my car is showing code 31, I thought is was the wastegate solenoid, I read this post and pulled the ecm sol and it is blown. I'll replace and then see if it is the TCC, will stink to pull the tranny pan off after I just replaced the fluid and filter two weeks ago with zero miles. Should add to the spring cleaning for those of us newbies with original cars. This is also why I bet I can't jump my compressor low side switch to run compressor, the compressor will not come on. Thanks again for the detailed post, I have printed and added to my GN binder.
Joel

 

[Joeld]

vin7 - Is it the power plug to the clutch that needs attention and tape as a potential short culpret?

 

[VIN7]

Its the plug directly behind the ac clutch pulley, has green and black wires. You should see what appears to be a resistor in the plug. The legs are bare on the resistor and if they touch anything it will pop the fuse. Wrap tape around it real good and it should be good to go.

 

[Joeld]

Understood will tape it up tomorrow night after work before I replace the ecm sol fuse, if it still pops then I'll check the TCC solenoid, thank you Mike