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'99 Deville-Need heater help


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Ok All, my '99 Deville isnt blowing heat on drivers side, pass side is like the desert. First off, only code is IPC U1255 Class 2 Comms Fail (which was there when I had heat). I have replaced the drivers actuator 3 times, replaced the A/C Module and flushed the hell out of the heater core ( Frontwards, Backwards, with chems, without, with shop air and without...) Pass side blows HOT and drivers side cool. This is same for A/C on AND off. What else could it be, the temp sensor in the duct??? To let actuator and module relearn, I disconnected the batt for 30 mins, then onced hooked up, let ignition left on for 3 mins, also, turned up, then down all of the way a bunch of times. HELP!!!

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The first thing you should do when diagnosing most problems is run the OBD codes, which you can do from the front seat in your Cadillac using the A/C buttons and the DIC; see the link in my signature block below. Please run the codes and post them here.

But it does sound like a vacuum line is off, or that there is a stuck temperature servo. The OBD codes will tell the tale.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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