Over-heating, possible cause?

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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, Over-heating, possible cause? in Past Cadillac Vehicle Discussion; So I've been at school and haven't driven my 2000 Deville too much. A couple months ago I noticed that ...
  1. #1
    Strappingyl is offline Cadillac Owners Member
    Automobile(s): 2000 Deville
    Join Date
    Sep 2011

    Over-heating, possible cause?

    So I've been at school and haven't driven my 2000 Deville too much. A couple months ago I noticed that I could not get any heat from any of the vents in my car. I didn't see it as much of a priority because I only drove it once a week, and I go to um in Ann Arbor, so it doesn't take long to get anywhere. I just dealt with the cold because I never had time to really look into it until now.

    Then when the weather started to warm up a little outside, one day I noticed my temperature gauge was one bar above the middle-most temperature (I have a digital cluster). I thought that was odd, considering it's never happened before during the 2 years I've owned it. As the weather got warmer, it got to the point where I got the "Engine Hot AC Off" message.

    Now I can't drive it in weather that is above about 70 degrees unless I really baby the engine. Even on the freeway at midnight when it was 40 degrees, the temp gauge was pretty much always one bar above the regular temp (sometimes going to regular, only lasting a min or two before jumping back up to one or even two bars).

    Could the two issues between my car not putting out heat in the cabin and the engine over-heating be connected? I didn't drive it enough (and it was winter) to notice if the engine was just staying cool because it was so cold outside (meaning that the issue that is preventing heat from the cabin is most likely causing the engine to overheat, too), or if the engine is overheating because of some other issue unrelated to the heat not going through the vents.

    What I do know is I have no leaks and the coolant level is fine. I'm about to go outside and pull some codes, I'll post those (and their defs, don't worry) in a few.

    Thank you,



    DIM P1536 HISTORY - A/C System - ECT Overtemperature
    IPC U1000 HISTORY - Class 2 Communication Malfunction
    IPM BO249 HISTORY - Heater/Defrost/AC Door Range Error
    IPM B0419 CURRENT - Air Mix Door #2 Range Error
    IPM B0423 CURRENT - Air Mix Door #2 Inoperative Error
    IPM B0429 CURRENT - Temperature Control #3 Rear Circuit Range/Performance
    IRC U1064 HISTORY - Loss of Communications with DIM

    I didn't clear the codes before I did this. Should I?

    Thank you,

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  3. #2
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
    Automobile(s): White Diamond '03 DHS (with DTS floor shift)
    Join Date
    Jun 2004
    Woodstock Ill.

    Re: Over-heating, possible cause?

    Those B codes could well be your cabin heat problem.

    Engine temp might be a clogged purge line.

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