I have a 99 300m. The air conditioner just stopped working. The compressor is not turning and I checked the voltage to the clutch and it isn't recieving any. I also swapped the ac relay with the wiper relay but, it still does not energize. It blows air out the vents but it is not cool. I also tried to charge the system with freon but it would not accept any. I used the low valve on the compressor. Is this the correct valve or is there another one in the system. Has anyone seen this, or do you have any other ideas for me to checked? Is there any way to check the low pressure sensor? Thanks

 

humm lets do some basic stuff first see if u have a control issue,compressor issue or freeon fill issue.
Sence u asid u checked the freeon and its fill and u swapped out relays and checked for voltage at the compressor then s lets see if u have something that will not allow the compressor to come on. Do this first at the relay with a volt meter. Start the car u will have 2 12 volts power sources. One with the power to hold the clutch and one that holds the relay closed. If u have thoes then we are good there. Next get a jumper wire and with one of the 12 volts power supplys jump it to the clutch side and see if u hear the clutch cycle as u apply and take away the power. Oh yeah that will be pin D on the relay see the attached pic. Pin A and B will be your power supply and pin C will be ground from the pcm to tell the relay to close with the key on and the ac turned on. Let me know if u have all of that above then we can see whats next. I would say jump the pressure transdusor but u cant this one is a voltage return sensor and not just a pass though to ground sensor.

 

Thanks for the reply. I will try these checks this afternoon. I know I had 12v at 2 pins. I didn't see the attachment of the relay pin numbers. Thanks

 

oops

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I'm having a hard time determining pin numbers on the schematic. I think they might be in this configuration. C F A for the ac compressor. Is this correct? Thanks
D
B

 

I checked the voltages this is what I had with the car runninga/c on and the relay pulled looking down at the socket. 0v blank 13.42v
0v
0v Thanks

 

alright this is what u need then here is the wireing diagram and u are missing a 12 volt source I would say the control side. Check the 2 fuses on this diagram and see if they are good if so then u have bad connection, bad wire or broken connection. THE PDC is outside the junction block is the one inside on the driver side panel.

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Fuse 21 was good. Fuse in the pdc was marked (rad fan) 30A it was bad swapped it with another 30A and it blew again. Is there a certain amount of resistance I can measure across the clutch? I will be away for a couple days. Thanks Again

 

that 30 amp fuse is the same one for the power supply to the clutch. In that case u need to see if the rad fans are the cause of the high resistance or the compressor is the one making it pop. Unplug the compressor and start the car up turn on the ac or just let the car get to the point where the fans come on and see if it pops it then I ahve seen both where fans pop that fuse and the comperssor pops it. U cant check the restance across teh comperssor untill its turned on and running and that will blow your ohm meter what the volts. U can spin teh fan motors and see if one or both turns harder then the other.

 

OK I'm back, I disconnected the compressor p/j and it does not blow the fuse. The rad fans alsocome on after car heats up. Is that plug jack for the clutch only? What's next? Thanks