Heater fan posessed?

[KillerBob]

Hello everyone, love the site. I'm hoping someone can help me out with this issue. I only had one fan speed (high) so I went out and bought a resistor..just before putting it in my fan started growling, so I figured it's shot and thats what killed my resistor...fair enough. Changed them both (super fun) and they work fine. Drive to a buddy's, shut my truck off and fan stays on for a sec then shuts off...weird. Come out later, fan is blowing with no keys in, batteries are dead, -30...no start with boost, got it towed...fun. Anyways, since then my fan will work when turned on, but will sometimes turn on with the keys out or in the off position. All the wiring seemed fine. I thought maybe a resistor coil was touching another coil cause they were close when I put it in, and sure enough it seemed like they might...I seperated them and put it back in..same thing. I've been pulling the black wire off my fan every time I leave the truck for awhile and it's not the coolest thing, and I'm sure to forget it again. Any ideas?
Oh yeah, I also only have high beams, so I checked out the back of the multi function switch and there were some bare wires touching...can't get at it to fix it though...how do you get the top steering column plastic piece off? The key hole seems to be too small unless you can take it out?
Thank you everyone.
Richard:confused:

[DmaxMaverick]

Yep. Call a priest. She needs the Linda Blair treatment.

Sounds like wiring gremlins. Typically grounds. I'd also suspect the ignition switch (fan stays on). Does the fan turn off when you move the selector to off with key out (or with an electronic HVAC, 92-94, just off, before key off)? You didn't specify the truck year. You may also have to remove the steering wheel to get that trim cover off without destroying it. Sounds like you may have a ground problem in the dash, in any case. Also, depending on year, the high beam circuit may be energized by a completion to ground, in the multifunction switch. Or.... Yep. Get a priest.

[KillerBob]

It's a '96 GMC 1500. It seems to do it regardless of the key posistion or if the key is in it or not. The high beam only works when its turned on, when clicked to low beam it just has the sig lights on...back lights work fine.

[DmaxMaverick]

Difficult to say. Verify you have a good ground to the dash and column. If it's good, I'd suspect a problem with the ign switch (not too uncommon). Not sure how the high beams fit in, but it may have something to do with the DRL's, if you have that (not sure about '96). Either way, poor grounds are very common, and usually the root of most electrical issues on these trucks.

[KillerBob]

Thanks..do you know where the ground is located for the Dash? It's a Canadian truck so it has Daytime running lights but they haven't worked since I got it...but the lows worked fine...I'm guessing that has something to do with the bad wires on the multifunction switch...I can figure that out but the fan sucks lol.
Richard

[97-6.5TD-F]

First I would remove the hvac control module (the three dials for heater control) and check the connector right behind the fan switch. They are notorious for melting and causing all kinds of fan problems. As for the headlights if there is bare wires making contact off the m/f switch that is more than likely the cause of that problem. To get the ignition cylinder out is a bit of a pain, first rmove the lower cover, then you have to pull up on the top cover and find the hole in the ignition cylinder housing. Then youhave to turn the key to the start position,(i put the shifter in r or d so the engine isnt cranking when youj do this), then push the pin in the hole with a small pick or likewise. Then the cylinder will simply pull out.

[Robyn]

These sort of electrical gremlins can be nasty.
I am in agreement that you need to look to see if the plug has melted.
If not then I am suspect of the high blower relay being shot and allowing current to flow when it should not.
What can happen is the blower relay will get a buildup on the contacts over time and then when the power is turned off the contacts can't open enough to disconnect the circuit. This can also be an intermitent that due to hot and cold will make ther contacts make and break.

My Western Star had this happen on the AC clutch relay and it would not shut off. Its a very similar little black cube with a number of prongs.

Try giving the relay a looking over. Actually I would locate the relay and then get the fan to stay on and try removing the relay. If this stops the fan then I would say you have found the culprit.

This relay if stuck can and will run the fan regardless of the key position.

Good luck and let us know.

Robyn

[Patrick m.]

I agree with Robyn here, high blower has batt power all the time. If it sticks...fan runs regardless of key position.
When the key is on, and high blower is requested, the relay is turned on. The relay just supplies power to the blower for full speed so the switch doesnt have to. The relay could physically stick so it wont need to be turned on to supply power.

Of course if the blower is running at a speed other than high, the must be another explaination. (consider blower speed will be less in high position with out the engine running as supply voltage will be less).

[Robyn]

Depending on how good of a contact the relay is or is not making the fan could be receiving power through a really bad arced up contact and not run very fast.

Some systems run everything through the relay including the high speed. The lower speeds are directed through the resistor set after the relay.

Check the relay take two asperin and call us in the morning. :D

Robyn

[KillerBob]

I checked the hvac...it seems okay. The relay seems like a prime culprit...it seems to go into high fan speed when it does it's mystery turn on. Is this the black plug thing that is close to the resistor? I really appreciate the help from everyone. I'll try to check it out tomorrow if I can find it. I'll keep you all updated.
Richard.

[KillerBob]

Or is it with other relays in the engine fuse box? I'm sure if I look around enough I should be able to find it...it's dark and cold so I'll save it for tomorrow though.

[bsevans]

I went through three climate control panels. The dealership admitted that the units that came with the '95/'96 model year eventually always have the fan on at a very low speed. You can buy the control moduals that connect at the back. I replaced the entire panel twice under warrenty and once out of pocket. The last one installed has a different feel to the controls. GM clearly changed the design. It has functioned without problem for at least 5 years (too lazy to pull the paper work).

[allformike]

to add to the headlights, i would do a simple check and see if the low bulbs are blown, if your lucky it could be as simple as some new bulbs.

[KillerBob]

Well, I finally got around to changing the relay...not hard as you can just do it through the glovie. Seems to have fixed it (fingers crossed) no crazy fan as of yet. Thanks for the help everyone, and I'll let ya know how the low beams go when I get to it.

[KillerBob]

Well, it worked for a few days then boom...possessed again. When its running it will come on in the off position and it seems to turn on and off the the revving of the engine...sounds crazy but thats what it does...how could the revving of the engine make the fan kick in and out. It's not always the case, but if I tap the pedal repeatedly the fan will do the same, although it still come on at other times once and awhile, like when the key is out! Any ideas anyone?

[Turbo Al]

It is dark out and I am afraid of the dark, First thing tomorrow I will go out and take a look at mine (1993) and see if there is a control module on the firewall. Believe it or not I just went through this whole proccess just as you decribed but on my 1993 Caddy. The temp cure was pulling the A/C fuse untill I got the part.
Al

[Turbo Al]

Ok near as I Can tell there are two relays one for high fan and one for low. Unfortunately it looks like they are under the dash somewhere -- I wish I could tell you where but I can't crawl around under the dash (I have a broken leg) right now. I would think the reving of the motor (vibation) may be kicking the relay in and out.
Al