99 Grand Am GT Air conditioning problem

evo-00 · 05-11-2009, 05:28 PM

I have a 99 Grand Am GT with a 3400. The air conditioning is charged up but compressor won't run. I checked for current at air compressor and there isn't any. Fuses are ok. Any ideas?

Rich Good

xeroinfinity · 05-11-2009, 07:44 PM

Thier are a some relays in the underhood fuse box, those could be toast.

#16 is for the compressor specificly, and I think #37 also covers the AC. #3 Mxi fuse is also something to look at, especialy if a radio was just installed, they're on the same circuit.

brcidd · 05-11-2009, 10:58 PM

It takes 47 psi to engage compressor- does your gage show that?

evo-00 · 05-12-2009, 10:53 AM

I have 56#s of pressure at the high side and 60#s on the low side. I swapped the fuel pump relay with the ac relay and still compressor won't kick on but the car starts. Also fuses #3 and #37 are ok. Now what? Need more help please? I appreciate the replies.

xeroinfinity · 05-13-2009, 03:30 PM

Sounds like you need a scan tool that can read AC DTCs to figure this out. Other wise you're just guessing and could be throwing money away.

Or have you had it scanned for trouble codes ?? and what are they ?

stoynuts · 05-20-2009, 10:44 PM

Are you getting any signal to the relay when you engage the a/c? your swith could be bad.

3100 · 06-01-2009, 03:39 PM

do you have any other electrical problems on this car,
find that AC compressor clutch relay, start the engine put your finger on that relay while someone is commanding ac on and off listen for the click in the rely if not then you could have open before the relay, HVAC swithc, bad bcm, open in ckt 459 from pcm to terminal 85 of the relay. 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.

evo-00 · 06-02-2009, 10:49 AM

Prob. fixed. Took it to a pro. It was a pressure switch that controls when the comp. kicks in. Thanks for the replies.

MHardee · 06-02-2009, 10:42 PM

>>>Prob. fixed. Took it to a pro. It was a pressure switch that controls when the comp. kicks in. Thanks for the replies.

What switch was bad? I think I am having the same issue..

MHardee · 06-02-2009, 10:47 PM

Quote:

Originally Posted by 3100

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.

Where do you jump from and to to "force engage" the compressor? I am working on my son's and thought it was low on gas. Hooked up gauges and when compressor is NOT running, I see about 110 psi on low and 95 PSI on high. Seems as if it has ample charge to engage compressor, but it does not engage..?? Where should I go from here?

Thanks..

3100 · 06-04-2009, 03:33 AM

here is the picture of the swithc

MHardee · 06-04-2009, 10:04 AM

Quote:

Originally Posted by 3100

here is the picture of the swithc

Thanks for the reply. Is this not the high side switch? I saw it and it has three wires going to it. I am familiar with switches that are usually located at the accumulator that have two wires. (As on my 97 Blazer) and have jumped them to bypass before.

Am I "barking up the right tree?".. If the system has 96 psi static, should that signify that there is gas in the system and enough to alow the clutch to engage?

Thanks for any help..

evo-00 · 06-04-2009, 01:06 PM

Pic isn't exactly right since the GTs have a 3400 but it is similar. The switch is directly below the high pressure connection point. To engage the comp. pull the relay and use a jump wire in the connection points. I forget which spots though and don't know if you could burn something out this way.

brcidd · 06-04-2009, 11:17 PM

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....

3100 · 06-05-2009, 12:05 AM

Quote:

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....

- 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.

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