Heater Fan Coming On By Itself

[chuckluv]

Hi guys,

I have a strange problem which has occurred a few times in the last week. 3 times now I have unlocked my car, gotten in and heard a loud humming noise coming from the dash area. Then realised the heater fan is on about medium speed and air is coming out the centre dash vents. The only thing that stops this is by turning the ignition switch to the on position.

I've tried a few things to see what might be triggering it, and it doesn't seem to happen if I turn the fan off before I get out of the car (dual zone climate control). SO far that is all that stops it.

Twice now the car is slow to crank due to this problem, and once I needed a jump start. Lucky I have a deep cycle battery I guess...

Before I potentially start spending hours of time diagnosing this, has anyone experienced this or have a clue what could be triggering it to happen. It just seems weird that everything is fine when I turn off the car and then come back and with no key in the ignition the fan is on.

Thanks

[Doddo22]

Use a multimeter to check the positive cable to see if you are getting constant 12v or switched 12v when you turn the key.

That would be my first step

[Ralph Wiggum]

Are you sure its the heater fan you can hear and not the fan for the cabin temp sensor?

Both my Dual Zone ICC's do the same. Next time it happens place your thumb over the small vertical slots on the RH front face of the ICC. If the noise changes it's probably just the Cabin Temp Sensor.

[chuckluv]

Sorry for the late reply

Its happened a couple more times now and turning my heater fan off before turning the car off isn't helping anymore :(

It is definitely the heater fan coming on as there is a strong flow of air from the dash vents.

Reading up on some other forums I have seen that the HIM module can be faulty causing this problem (although most other people are saying that the fans come on all the time). Alternatively, ive also read that the thermo fan connectors at the radiator can become contaminated causing a current back feed to the HIM, once again causing the inside heater fan to come on.

Does this sound plausible?

[Doddo22]

mmm I dont know if that would be possible as its on a different circuit, and your radiator wont run with your car off anyway so that still doesnt make sense even if the plug is shorted somewhere

I would guess the relay for the heater fan is faulty which can be found in the fuse box I believe

[chuckluv]

I think I found the culprit.

in front of the airbox there are 2 large black electrical connectors. I opened them both up and found one was full of water and was full of corrosion.

I dismantled the connector, cleaned all the terminals with a wire brush and contact cleaner spray. then put it all back together and the problem hasnt re-offended.

I can only assume there was a current back feed into a ECU or relay somewhere causing my heater fan to come on.

I was goiing to upload a pic of the plug and the corrosion,but cant figure out how

Anyways, so far so good.

[Doddo22]

bottom right corner of post are there is a button : 'More reply options' use it

[vixenf6]

Poltergeist ?