Today when I was coming home my heat would not come on. The climate control turns on and seems to be functioning fine, but the fans just do not start. I tried playing around with the fan speed etc..and nothing would turn it on.

Any ideas? I need to fix this asap as I need the heat everyday

If you have the Automatic Temperature Control (ATC) then there is an electronic module in the top of the fan duct to the passenger side of the fan motor that often fails. See the blower schematic in the factory service manual (section 8A-66) and you can jumper the two hot leads between the two connectors. If the fan comes on high then you either have a bad module (most common) or a bad HVAC head.

Thanks for the help. I decided to give it another day. This morning when I left it turned on fine, and ran fine the whole time. When I came back home (6hrs later), it would not turn on again!

Does this change anything or would this still point in the same direction? Also, would it be a good idea to try the Auto Climate Control Diagnostics?

thnx a bunch

Are the fan icons on the HVAC control head coming on or not. If they come on, the next thing to do is to check for power to the fan motor (motor may be failing). If not present then check the control voltage (varies with fan speed command) to the control module and for the 12v supply to the module. If these are present but no power is going to the fan motor than it is probably the module.

The entire process is described in section 8A-66 of the factory service manual.

Comment: a bad ground can do the same thing.

The fan Icons do come on the display. This is freaky. For the past 3 or 4 days it has done the exact same thing.

Works great in the morning. (It gets hot fast, car is warm quickly)
Won't work in the afternoon. (fans won't blow)

Would it be the fact that it sat all night explain why the heat comes on?

This car pretty much only gets driven twice a day, and it'* done this exact same thing every day. I don't have a service manual (or much how-to knowledge either ) So I will ask some friends to help me out with the process, or I'll take it to my local mechanic who I know well.

It'* just that if you think about it, if it were the things you mentioned, shouldn't that mean it should not work at all, or at least not in a specific pattern?

This afternoon I tried the front window defroster, auto, ECON, all with the temp set to 31C (highest heat) and nothing started blowing. The rear windows defroster works however :o.

anyhoo, thanks a bunch.

Typical electronics, works when cold and dies when hot. My bet is on the blower module since at this age they are somewhat notorious. If you can't troubleshoot properly (suspect even a Haynes will show the blower module) then the only alternative is to throw parts at it and I'd start there.

Just be glad that you didn't have the failure that makes it impossible to turn the fan off.

Of course since I have two cars of that vintage that use that module, I grab spares whenever at the local pick-a-part. About 50% of the used ones work.

Is the module solid state? You could probably check it at the yard for functionality. Sorry for me not checking my FSM.. it'* kinda sitting in my passenger'* seat, and unfortunatly my car is covered in about 7" of snow :(.


-justin

i have exactly the same problem. just in time for the winter!
let us know when you figure out what was causing it

lol, I guess I'm not the only one with the possessed Bonneville. I'm probably going to take here to my friends Dad, who is a mechanic out of his garage at his house. He has a 4-car garage with two hydraulic lifts and other the other car-fixin goodness. I will try and get whatever part it needs from the wrecker. How much does the blower module (and I guess other possible parts) usually sell for? I don't have alot of cash right now, and it would be a shame to have to park the Bonne for winter over something so silly (or I'll have to learn to drive without breathing on the windshield ). I also just got my insurance renewal bill, so yea...

Also, about the electronics being hot...it does sit for 6 hours out in the cold when it doesn't work, but who knows there are alot of possibilties. I will keep everyone up to date.

thanks!

Hey I got the same problem and just when the cold weather comes eh
what a pain.. my fan blows so rough that it shakes the pedal and I know this cause when I change the speeds it stops, but my fan also fails .. sometimes it works sometimes it dosent, im gonna try that drilling a hole and adding a little bit of kerosne oil to lube the fan up.