A/C Compressor No Power

On our '97 Park Ave I have no power at the connector to the compressor. We bought the car in March here in Omaha and it was cold and like a true novice I forgot to look at the compressor to make sure the clutch was engaged. Now, after doing an engine swap the last thing I have to fix is getting the a/c to work. The blower works fine, the hearter works we just didn't have any cold air blowing so I was going to re-charge the freon when I noticed the clutch wasn't engaged. In troubleshooting, I never get voltage at the wires. I verified the micro-relay works and has voltage as well as the fuses. I am not sure if the compressor gets it's voltage signal from the a/c-hearter control panel or what exactly.
Any ideas please let me know...
Thanks, myers_8

Your post has been moved to the Buick PA Forum.

The PCM module will not energize the A/C clutch relay and therefore the compressor doesn't kick in until the refrigerant pressure/charge is acceptable. There is a lo/hi pressure sensor.

So recharge with the right amount of R134a and see what happens. You should pull a vacuum of the system first.

Well don't feel bad, you couldn't check the compressor anyway as it only works above 50 degrees...

No, this is a 3800 series II in a 97 Park Ave. Everything works meaning the blower fan, heater etc. The clutch never engages on the compressor and I thought it had to fire before you can charge the system? Like I posted earlier, I have voltage everywhere logically where it is suppose to be except at the connector behind the compressor, there is no voltage there. The guy that did the other answer to this talks about making sure it has a charge first but I thought the compressor had to be engaged before you can re-charge the freon? Is that true?
Thanks, myers_8

No, this is a 3800 series II in a 97 Park Ave. Everything works meaning the blower fan, heater etc. The clutch never engages on the compressor and I thought it had to fire before you can charge the system? Like I posted earlier, I have voltage everywhere logically where it is suppose to be except at the connector behind the compressor, there is no voltage there. The guy that did the other answer to this talks about making sure it has a charge first but I thought the compressor had to be engaged before you can re-charge the freon? Is that true?
Thanks, myers_8

Myers_8,

Your original post was moved to the Buick Park Avenue forum so check there for any replies. Your current post will be moved there too. Please keep make and model at the right forum.

The lo/hi is in the line directly behind the compresor on one of the hard lines isn't it? I guess things have changed a bit in the past few years, it used to be you couldn't charge the system unless the clutch was engaged and the system running before it took any freon? I just have a canister and line connector to charge a large can into the system, you said I need to pull a vacum, are you talking about pulling a vacum out of the hard line a/c system?
Thanks for you help,,
myers_8

I will check the diagram for it now, be on line if you have time...3100

Ok. PCM receives signal from pressure sensor, if pressure is too low or too high pcm (computer) will not ground terminla 86 of your ac clutch relay. What you can do to try to charge it with some freon is connect the 134a can to your low side connection, remove ac clutch relay and see where the terminal 87 and 30 of the relay diagram go to. Jump those two wires with piece of wire while engine is running and see if clutch engages if not and if 10A ac clu fuse is OK you will know that you have open somewhere or the clutch is not working. To eliminate open you can wire ac clutch straight to battery 12 volts if clutch engages you have open somewhere if not it is a bad clutch.

The lo/hi is in the line directly behind the compresor on one of the hard lines isn't it? I guess things have changed a bit in the past few years, it used to be you couldn't charge the system unless the clutch was engaged and the system running before it took any freon? I just have a canister and line connector to charge a large can into the system, you said I need to pull a vacum, are you talking about pulling a vacum out of the hard line a/c system?
Thanks for you help,,
myers_8

The one the PCM module uses is over by the accumulator.

You use a vacuum pump to evacuate the system. Get the reading to around 28 in-hg after about 30 minutes to one hour and then recharge. But first check the low side port and see what the current charge is or if it is low.

Kewl man, thanks I can follow that easy enough. I knew there was a way to hot wire the clutch to see if it would fire or not. I will go out there and do that this morning. Thanks again for your input. I am a system's engineer by trade but sometimes I get a little stumped. The systems have changed a bit over the years, because many years ago when I was working in a shop the clutch had to be engaged and running before the a/c system would take freon, and by jumping those connections at the relay I will be able to make that happen.
Have a great day.
myers_8

hey 3100, thisis actually someone else's post and it got connected to mine the other day somehow. I don't own a Grand Prix, I am the guy with the 97' Park Ave. When I made a post the other day, it connected this post in line with mine and then mine was moved to the Buick Park Ave section, really weird.
Sorry for the confusion, but thanks for the help with my Park Ave, I did get the compressor to fire as soon as I gave it a little freon. the lo/hi sensor wasn't allowing the relay to fire until it had enough freon in the system.

hey 3100, thisis actually someone else's post and it got connected to mine the other day somehow. I don't own a Grand Prix, I am the guy with the 97' Park Ave. When I made a post the other day, it connected this post in line with mine and then mine was moved to the Buick Park Ave section, really weird.
Sorry for the confusion, but thanks for the help with my Park Ave, I did get the compressor to fire as soon as I gave it a little freon. the lo/hi sensor wasn't allowing the relay to fire until it had enough freon in the system.


good, so it was low on 134a, I hope that my posts were of some help to you.

No yo did great man, I appreciate it. I sent you a larger email explaining some of the issues, maybe you didn't get that one. After re-charging the freon, I watched it all leak out and make a mess blowing all around my motor. It seems the front seal or a seal is out in the compressor so I had to go find a new comressor today. Did good got one out of a 00' LeSabre with the same Ident# numbers for 80.00. Now I just have to R & R that project. Thanks again, I think this forum is outstanding.