99 Grand Am GT Air conditioning problem

[evo-00]

Originally Posted by brcidd

That is NOT a switch it is a 3 wire pressure transducer- that continuously feeds pressure data to the ecm to turn on fans to turn on and off compressor if pressure is too high or too low- You cannot jumper it- no need to if you have more than 47 psi in the system....

Just trying to test the compressor to see if it works and yes you can jumper it. Also sorry my jargon wasn't specific enough. Transducer = Switch although I think everyone knew what I meant.

[MHardee]

Originally Posted by 3100

- you are right but we can't get so technical with the general public so we can call it a switch, and you know in automotive industry people call parts the way it is easier for them to memorize.
-and many techs still call it a pressure switch,
-do not jump the switch,(transducer) but disconnect the ac compressor connector and at the compressor terminals connect two jumper wires to the battery (do this with engine off and you will see clutch mowing in and out when you connect and disconnect power. if not then ac compressor is bad.
or if you want to diagnose more find the AC compressor clutch reley, start the engine put your finger on that relay while someone is commanding ac on and off and try to listen or you can even feel the click in the rely if not then you could have open before the relay, HVAC swithc, bad reley, bad bcm, open in ckt 459 from pcm to terminal 85 of the relay. If you disconnect the relay and command ac on then connect dvom leads between the connectors that go to 85 and 86 you should get battery voltage, and this will tell you that your fuse is ok, that pcm and bcm are doing their job. you should also get battery voltage between the connectors that connect to terminals 85 and 30 of the relay when reley is disconnected.

Thank you very much. At last, an intelligent answer! I took the car to a professional yesterday for diagnosis. He ascertained that either the compressor was bad or the clutch had a short. It blew the fuse again. So, I have ordered a compressor, accumulator and orifice to replace. The car has 100K on it and was nervous about just changing the clutch out. I have not had a chance to turn the compressor by hand (it's my son's car) to see if it was seized. I kinda doubt it as it engaged for a second at the shop. My hope is now that I can get 47 PSI into the unit after a vacuum without a low side switch to jumper..

I will try your checks on the relay.. Thank you..

[InfiniteVision]

Originally Posted by 3100

...If you disconnect the reley and comand ac on then connect dvom leads between the connectors that go to 85 and 86 you should get battery voltage, and this will thell you that your fuse is ok, that pcm and bcm are doing their job. you should also get battery voltage between the connectors that conect to terminals 85 and 30 of the relay when reley is disconnected. Also you can jump your compressor to positive and negative to see if it is working at all. let me know what the results of your testing are so we can take it from there.

3100-
I'm not getting power to AC compressor clutch nor does the relay click when the AC is turned on. I checked 85 & 86 and 85 & 30 relay terminals and there is no power when the car is running and the AC is on. I jumped 12 volts directly to the AC compressor and it engages. Fuses 3 & 37 are OK. Can you please tell me the next step to diagnose where the problem lies?

Thank you very much!

[xeroinfinity]

Welcome to AF InfiniteVision !!

I'd say your relay is bad.

I wouldnt just go jumping pins here and there. You are likely to burn stuff up and cause more problems.

The pro's can , or should be able to, narrow down all AC problems.
Even if someone knows it's a compressor or high pressure switch, you still need the refrigerant pulled out with a machine, and a vacum pulled when the repairs are made to refill the system. Which you have to know how much refrigerant and how much oil, exaclty or you'll just screw up more components.

And you're likely to replace things that dont need replaced, they can be pricey!!

Good Luck

[InfiniteVision]

Originally Posted by xeroinfinity

I'd say your relay is bad

Thanks for your input. I swapped it with the horn relay and still no clicking or power to the AC clutch. The horn also worked with the AC relay, so unfortunately it's not an easy fix.

[3100]

Originally Posted by InfiniteVision

Thanks for your input. I swapped it with the horn relay and still no clicking or power to the AC clutch. The horn also worked with the AC relay, so unfortunately it's not an easy fix.

you are not getting any power because pcm is not grounding the relay due to the low ac pressure. If it is below 35 psi, and if, IAT temperature is below 41 F, and if engine temperature is higher than 124 C, and if throttle plate is open more than 90 degrees thsi are some of the reasons when pcm would prevent ac clutch to engage.

Here I bet you it will work when you do this: disconnect ac reley completely turn it upside down and see where the terminal 87 and 30 go to, then just bridge those two connectors with a short piece of wire while engine is running and ac is commanded do this only for 2-3 sec to verify that everything else works and that there is no opens, it is definitely because your pressure is below 35 psi.... again just bridge the wires for 87 and 30 with reley disconnected ac turned on engine running you should see it engage. then come here to tell me what happened. Autozone sells 134-a cans

[xeroinfinity]

Ok 3100 what makes you say its under 35 psi ??
He's not mentioned any readings for his AC.

I'd just check for power at the compressor connector and fuse box pins. And check for conitnuity for the black(grnd) wire at the compressor connector. So if you have power/grnd down there then it's likely the compressor clutch is defective.

If the all other circuits and relay is good, and your system is fully charged with refrigerant, and your compressor still isnt working, then you'll need to have the PCM tested and its related circuits.

[InfiniteVision]

3100:
Bridging the wires for 87 and 30 have no effect.


xeroinfinity:
There is no power at the compressor connector. Directly jumping it activates the clutch.

There is ground continuity at the connector.

[3100]

gentlemen go here: http://i28.photobucket.com/albums/c2...wiringdiag.jpg


study this diagram and if bridging 87 and 30 did not work, it is possible that fuse is blown, or there is open after the fuse or in the ground (grey wire that connects to ac compressor)
1. this would be my final test: disconnect reley, ignition key to ON position, connect DVOM or test light one side to battery negative and the other to the wire that connects to terminal 87 of the reley. (if you test light goes on, or you get battery voltage - fuse is good and that side of wiring is good), next disconnect the connector at the ac compressor the grey wire is ground to ac compressor connect the test light or dvom between battery positive and the grey wire when ac compressor connector is disconnected (you should see test light come on or see battery voltage with dvom, if not then there is problem with ground side) reley terminals are not shown on this diagram but 87 and 30 are on the right side of the reley (top and botom on the right side).


XI - pcm controls the ground for the reley, and if all the parameters that I mentioned in my previous message are in specs pcm will ground the reley. The reason I say it is pressure because it is most likely the reason the car is 10 years old and will most likely loose some freon. To diagnose this better it would be good idea if Infinite vision tells us how did his AC behave in the past. Was it blowing cold air less and less from year to year or it suddenly died.?

[xeroinfinity]

Yeah, something else I think that plays into this is the cooling fans on the radiator. If either of those relays or fuses are bad, the ac doesnt work.

Good Luck

[InfiniteVision]

Originally Posted by 3100

gentlemen go here: http://i28.photobucket.com/albums/c2...wiringdiag.jpg


study this diagram ...

Thank you very much 3100. I hope to check out what you mentioned sometime today. Possibly this evening when it gets a little cooler.

This is my wife's car and due to illness it hasn't been driven since last summer. At that time the AC worked fine and was strong. My first thoughts were that mice might have chewed some wires, since it's been parked outside and not used for so long.

[3100]

sure any time, just remember key to on position because fuse is only powered when in on or run position.

What we did by bridging the 87 and 30 is bypassing the relay and psi swithc. So Pcm did not have any control but you did not see clutch engaging. Again just in case you will not see anything rotating it will be just slight in and out movement of the clutch.

thanks for the fast reply,

[InfiniteVision]

Too hot yesterday, too wet today... maybe I'll get to it tomorrow!

[jmacado]

Try one more thing. I have a '99 Grand Am and the A/C just quit working. Just blowing hot air. Noticed that the clutch was not spinning either and checked all the diodes and relays which were all ok. Figured the clutch had gone out. Just about to replace the compressor when I found that the wiring plug that goes into the clutch on the front of the compressor was cracked. When I wiggled it, the clutch ingauged. Stupid. A stupid piece of cheap plastic was causing the whole A/C not to work. Check that connection before you spend a lot more time just to see if this might be your problem too.

[InfiniteVision]

Originally Posted by jmacado

...Check that connection before you spend a lot more time just to see if this might be your problem too.

Thanks for the info but since there is no power at the connector something else is wrong.

3100:
I hope to check it out again today. Last week turned into a mess when my laptop decided to spontaneously combust (actually it just melted from the inside out) and my refrigerator pooped out. :-O