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AC Inop


Riverfurm

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Hi.... I am new to the forum. Just bought a 99 Eldorado's in good shape. The ac was inop found the system was low on a charge (low ac charge message comes up on info center). The compressor seems to be locked out so I can not recharge the system. I also have one code in the system for an air blend motor not working (forget the code number). Scan the system with a Mac scan tool and found in the data that the computer states their is no command to turn the AC compressor on. Is their some kind of lockout in the system when the AC is low or when there is a code in the system?

I have cleared codes and disconnected the battery but still can't get the ac compressor to come on. I am waiting for the shop manuals that I order, but maybe someone has some info here.

Back in 97-98 I used to work at a Cadillac dealer but I can not remember how to get the AC system to come on.

Thanks for the help!!!!!!

Riverfurm

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You need to see if there is any refrigerant left in the system. If there is, you can get a can of refrigerant hooked up to the system and then clear the code. Simultaneously press and hold the OFF and PASSENGER WARMER buttons to enter diagnostics. When you see PCM? push fan down to answer "NO". Continue until you see ACM? then push fan UP to answer yes. The ACM CODES? will be displayed. Again answer "YES" by pushing the fan up button. Then CLEAR ACM CODES? will be displayed. Answer yes and then exit diagnostics by pressint the AUTO button (round temp dial). You should then be able to start the engine and press AUTO to start the A/C. The system should pull in the can of refrigerant before the code sets.

If there is little to no refrigerant in the system, you will need to have it evacuated and recharged.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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the computer states their is no command to turn the AC compressor on. Is their some kind of lockout in the system when the AC is low or when there is a code in the system?

***************************************

The Low-Pressure switch is doing its job. I applaud your having the sense to get a FSM for your vehicle! Follow KHEs suggestion. You [really/b]should find/fix the reason the refrigerant is low.....

GM Reman 4.1 engine Dec '08

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When you have a low pressure message like that, if you delete or erase the codes the compressor will run long enough for you to charge the system, my guess is that something else is wrong.

Check the fuses for the AC COMP and put an ohm meter on the clutch windings to see what the resistance is. Check to see if the compressor is plugged in also, someone may have pulled the plug.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Needing to add refrigerant to a 10 year old car can be normal. If it were my car, after I added some refrigerant, I'd leak test the system.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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You guy are good and fast!!!! I will try the sugestions. This is somethng I should know, but when you get older somtimes you forget.

Thanks again

Riverfurm

I know what you mean, I recently said, I have forgotten so much, but I think its familiarization, once you get back into "IT", it will all fall back in place, its all logic. You are going to love the service manual

Welcome aboard, Mike (member formerly known as Scotty :-)

:welcomesmiley:

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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You guy are good and fast!!!! I will try the sugestions. This is somethng I should know, but when you get older sometimes you forget.

Thanks again

Riverfurm

Hehe, the memory is the second thing to go you know. Welcome to the club.

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You guy are good and fast!!!! I will try the sugestions. This is somethng I should know, but when you get older sometimes you forget.

Thanks again

Riverfurm

Hehe, the memory is the second thing to go you know. Welcome to the club.

But I forgot what the first one is. :D:D

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:lol:

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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if none of the above works you need to check out both thermistors one on low side one on high side directly behind engine up top one is right by the orfice tube and the other is right after on the skinny high side they can be malfunctioning and not even display a code you will have to check the resistance with a meter but be careful probing the sensor as it is real easy to bend the little pins when you check it don't back prob unhook sensor and test sensor directly with car harness unplugged from it I can't remember the resistance for the sensors based on ambient temp if you have a field service manual it will tell you or you can look up gm coolant temp sensor resistance values on google and they are very close, I had this same issue the day I purchased my 99 eldorado ETC

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Also very important if one of the sensors is indeed bad you have to evacuate the system as the sensor is in the refrigerant flow I made the mistake of unscrewing my low side one when replacing thinking it was just sensing temp through the metal what a surprise lost all of my freon so just keep in mind discharge system before removing sensor if one is bad Surprising both of mine were bad which is weird usually only one fails at a time, they don't last being exposed to raw refrigerant at extreme cold and hot temps

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AC working.... Jumped ac comp. relay, comp. came on. That means wiring good, comp. clutch good, comp. good. Evac. system, clear codes, recharge. Found #1 temp. control motor bad. Removed took it apart and found a bad pot. Will need new motor.

Thanks for all the info.

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AC working.... Jumped ac comp. relay, comp. came on. That means wiring good, comp. clutch good, comp. good. Evac. system, clear codes, recharge. Found #1 temp. control motor bad. Removed took it apart and found a bad pot. Will need new motor.

Thanks for all the info.

Good job.

Thanks for the follow up and letting us know what the problem was.

It may help someone else later that has a similar problem.

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