1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48 in Past Cadillac Vehicle Discussion; I retrofitted my 93 Deville and it worked for a while but now my compressor wont come on. F11- High ...
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    Jonathan11 is offline Cadillac Owners Member
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    1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    I retrofitted my 93 Deville and it worked for a while but now my compressor wont come on. F11- High side temperature circuit problem, F12- Low side temperature circuit problem, F30 CCP to BCM data problem (I think this code only came on from the temperature sensor problem) F48- Low refrigerant. I tried resetting the codes and jumping the low side switch to add refrigerant and dye to find the leak and it wont work. I checked the temperature sensor readings on the on board diagnostics and they both read the same, as they should since the system isn't on. The high side goes up just a little bit and the low side slowly follows. My other readings were a little weird, in car temp reading 49, outside temp reading 39, I'm in Houston and it's 103 degrees right now and it was it on the dash. Please help me with a solution, I have to get this fixed and get this car sold. Do I need to replace the temp sensors? Or is there anything else I need to do? Thanks and sorry for the long post.

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    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    If the car thinks it's 39 degrees outside, any cabin temp you request is going to go into heat mode. Might need a new ambient temperature sensor.

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    Jonathan11 is offline Cadillac Owners Member
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    Thanks for responding. But what about the codes for the refrigerant temp sensors? They seem to be working, and they're readings are the same, as the should be since the system isn't running.

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    onecool is offline Cadillac Owners Fanatic
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    Did you check the passenger side fuse? does the air conditioning clutch engage?

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    Jonathan11 is offline Cadillac Owners Member
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    The fuses are fine. The clutch is not engaging, I'm not getting voltage to the compressor. I checked the pressure switches and the codes are for the temp sensors but I have a reading on both so I don't know if that's the issue. I'm also hearing a static noise coming from behind my glove box where the BCM is and the heater core. I had to replace the leaking heater core a while back and I know it's electrical because it continues to do it when the engine stops running and goes away as soon as I kill the power on the inside of the car. I'm really stuck here.

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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    If you still have a low refrigerant code that is disabling the compressor.

    I'm also hearing a static noise coming from behind my glove box where the BCM is
    Do you mean an electrical arcing sound?

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    Jonathan11 is offline Cadillac Owners Member
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    Yeah it was just my speaker. I had the volume all the way down so I thought it was something else but when I turned my radio completely off, it went away. I cleared all the codes and jumped the low side pressure switch. I've read that when you retrofit, the r134a will give the temperature sensors a false reading because it's a different temperature than r12. I've read that it gives a higher temp reading than it should give so I installed resistors and it did bring the reading down but the compressor still isn't kicking on. Now I have no codes, the low side switch jumped so I can add freon, I have voltage and ground at the low side switch terminals, fuses are fine, temp sensors are working and giving a reading. Still no compressor.

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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    Maybe a bad clutch coil?

  10. #9
    aeronca36606 is offline Cadillac Owners Enthusiast
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    If you have a Factory Service Manual it will tell you how to go into the Diagnostics to see the AC Compresser command mode. On my 1985 you monitor the Outside Temp indicator. If the idicator is on then the computer is calling for the AC compressor to operate. If it dosen't run then you either have a wiring problem, Bad Clutch, or bad Blower Module. (I believe the 93 still uses the blower module to control the compressor) There are good troubleshooting flow diagrams in the FSM to solve just this problem. I just do not have your year.

  11. #10
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    I might be able to help, this is the correct year.

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    Jonathan11 is offline Cadillac Owners Member
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    Hey thanks for the help guys! I tried to turn on the compressor in the diagnostic mode and it wouldn't. And I'm not getting voltage at all to the compressor terminal. I think it maybe my control panel because I'm getting an input voltage but not an output to the bcm. That's what I thought it was to began with but my friend that use to work for Cadillac as a tech told me it couldn't be the problem. He said when those go out you see nothing on the screen and mine glows and works fine but it's weird I'm not getting an output voltage. I'm so stuck.

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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    Have you checked the relay Dennis posted?

  14. #13
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    That terminal on the BCM will be a ground in order to energize the relay. Notice terminals 2 & 5 are for the coil of the relay which will require a positive and a ground in order for the coil to be energized. Once the coil is energized the switch that is normally open will close and complete the circuit which will in turn energize the compressor clutch. It's a pretty simple circuit, just need to make sure the components are good. Without going back up through the posts, that fuse is on the passenger side behind the hush panel under the dash. If that fuse is blown you can also have irregular transmission operation.

  15. #14
    Jonathan11 is offline Cadillac Owners Member
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    Thanks for your help guys, it's fixed. I checked the relay and it had to be the fuse and I thought it only had the two a/c fuses. It was the fuse behind the glove box. Now with the resistors I put in the temperature sensor terminals I'm not getting the codes, a/c is blowing cold, shot some dye and found the leak, gonna fix all that tomorrow after I get a vacuum pump. Thanks again but one more thing, you mentioned that if the fuse is blown I could also have irregular transmission operations. Can you explain that to me?

  16. #15
    Wfossil1 is offline Cadillac Owners Member
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    Re: 1993 Coupe Deville A/C compressor wont come on. Codes F11, F12, F30, F48

    What size resistors did you use for the sensor terminals?

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