Vent turning on after car shut off

[chevygirl628]

Hey everyone,

So I went out to my Lumina last night to grab something out of it and hear a noise. So I get in and I'm listening and it was my floor vents blowing air at me. I was like wtf So I go for a short drive come back, turn my car off, and it still did it.....but I jiggled the hot/cold air selector and I hear it cut off and that was that. Then today I drove it again and turn my car off and I hear it start going again. I jiggled the hot/cold selector again and then pushed the vent button and then the off button and it stopped again. I've driven it a few times since and nothing.....is the blower motor going bad or is my car just messing with me right now?? She is a 92 3.1 Euro w/90,000 miles on it....hasnt been running weird at all or have any problems. Any ideas or suggestions would be greatly appreciated

[jeffcoslacker]

That a new one on me. I've seen just about every other electrical component on cars malfunction and draw power with the key off, rear defrosters, voltage regulators, cooling fans, fuel injection (that one was cool...it would fill the cylinders and crankcase with fuel), etc, but not a blower motor.

I wonder where it's getting power feed from? It should be isolated from ignition feed with the key off. Is it getting feedback from another circuit?

Do you hear a relay click when it turns off? Maybe there's one that's sticking and holding the power to the blower on after the key is shut off.

In fact, that seems most likely to me. I'm gonna go with that. I suppose the relay control side could be ignition switched, but the actual feed side might be unswitched, and so if the relay doesn't switch when the key is turned off, the blower just keeps getting power.

That's my story, and I'm stickin' to it. (till I think of something better)

[richtazz]

I agree with Jeff, it's either a blower control relay or the blower resistor.

[comptech_69]

Check yor relays. I just replaced a relay in my car becuase I would shut off my car and the battery would be dead a few hours later. It turned out that my fuel pump relay wasn't disengaging fully, so it was leaking power to the pump. The easiest way to find an electrical short is to disconnect the negative terminal of yor battery, and hook up a multimeter to measure the amperage. Put the negative terminal of the multimeter on the negative termal of the battery, and the positive terminal on the multimeter grounded out to the body. Let the voltage stabelize, and than stert pulling fuses/relays. Wehn the amperage drops down a significant bit, you have found your problem. You would probably find it easier to have another person watch the multimeter since as far as I know all the relays for the HVAC system are underneath the dash on the pasenger's side.

[chevygirl628]

Thank you so much for the advice guys.....and since I've posted this my car hasn't done it since. It had me somewhat stumped because I hardly ever turn my vent on. In fact the last time it was turned on was over the weekend when I let my roomie and her fiance drive my car...so maybe my car's mad at me for letting me do that...I dunno. But thank you again

[comptech_69]

If it's an intermittent problem, it definately sounds like a relay.