'89 525, check engine light when heat is on

[delussional77]

Girlfriend drives an '89 525 (think it's an i ). Anyway, now that's in the dead of winter at good ol' purdue she constantly has the heater and defroster on all the time. At random points throughout turning the car on and driving the check engine light will come on and go off. When you push the sliders on the heat all the way over it will go away, like wise when the defroster is turned off the same will happen (it will go away), and sometimes when just the heat level is turned from 4 to 1 (or off) it will go off as well. I'm kinda perplexed by this problem. Thank god the M5 does not do this. Any ideas for troubleshooting or straight fixing the problem? The engine has about 120,000 miles on it (not bad for a 15 year old bimmer!!!)

[mankiks323i]

take it to an autozone if you have one in your area i think they will check your engine light for free. I am not a mechanic but i dont think the heater and defrost have anything to do with the light coming on. The check engine light is more of a emissions thing oxegen sensors etc. or even a gas cap loose sometimes will cause a fault reading used

[delussional77]

Originally posted by mankiks323i@Feb 10 2004, 12:40 PM
take it to an autozone if you have one in your area i think they will check your engine light for free. I am not a mechanic but i dont think the heater and defrost have anything to do with the light coming on. The check engine light is more of a emissions thing oxegen sensors etc. or even a gas cap loose sometimes will cause a fault reading used

i always thought the same thing, but seriously it NEVER will come on unless the heat or defroster is on....now i've never seen it during the summer, and i'm wondering if the AC does the same thing (i'm not prepared to put the AC on full blast in the dead of winter to see if it affects it). The thought had crossed my mind that it could be an electrical problem and for some reason when turning the on the heater or defroster maybe a wire is touching and setting off the check engine bulb.....i will take it to autozone. Still waiting for some more replies though.

[Torque]

as you said, maybe just something getting shorted out, which causes the light to come on...

also check the fuel cap, make sure it is not cracked or anything, and check that there is nothing disconected under the hood