QUESTION: I had my BCM replaced and the company told me that they had to leave my HVAC unpluged because high voltage in the return could cause the BCM to go out again and it could also damage other modules. I am now having problems with my parking lamps and taillights staying on unless I pull the relay. Could this be caused from the hvac?
ANSWER: Hi Mary, The body control module does turn on and off the park lamp relay so in theory it might be the cause of your problem. But more likely would be that the park lamp relay is stuck in the on position. Try switching that relay with the one for front blower motor which is nearby in the power box in the engine compartment to see if that then solves the problem. I haven't heard of the issue of protecting the bcm by not plugging in the HVAC. Can you tell me more about that history? Roland
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QUESTION: They said that high voltageon the ccd bus line was bleeding from the hvac control head and that shuts down bus communication between all moduules and is most likely the cause of the bcm to go out in the first place. I took my car to another place and they said they have never heard of that either so they reset the Hvac and plugged it back in. I also replaced the relay and that fixed the problem with the lights for a while but now it is back
Hi Mary, I still would try switching the relay with another one just like, as I suggested, just in case the new relay went bad. The next one forward is the starter relay so don't switch it with that but the next one is the front blower so switch it with that. If the front blower then starts blowing uncontrollably and the lights are then off that would be the answer. But if the situation remains the same, it may be that the headlamp switch is not sending the message to the body computer to turn off the parking lamps (e.g. it has failed internally) so that should be checked with an ohmmeter which I can tell you about how to do. If the switch is O.K. then either the wire from the relay's in-board pin socket is shorted to ground or the body control module is incorrctly shorting it to ground. In that case you might disconnect the HVAC's blue plug (remove the bezel surround, then remove the screws that hold the HVAC controller in place and pull it forward to get to the blue plug on the back side) and see if that solves the light problem. Let me know what you determine and we'll go from there. Roland PPS: Thanks for the rating and nomination. You can do it again as regards this answer if you choose.