Fan - tastic Pontiac

Where is her professional mechanic brother (four year degree and major dealership trained)?

Seriously, he would be the one to ask.

Sticky fan relay, maybe?

Her brother obviously does not have the tools to examine that kind of quirk with him. He looked at that and said that short of dragging it into the shop for a thorough investigation, he could not answer that. Don't expect that to happen soon. My daughter has more than half her check eaten up by school payments, and the other half by rent. (yes- we're still paying a number of her bills at 1 to 2 years from retirement) So unless her brother is going to pay the bill, the car will not be going to an equipped shop in the near future. So far the battery is holding up to the extra load after charging is done.

Just wanted to see if anyone had any ideas on how this could be happening.

I feel your pain.

Maybe you can swap the heater relay with another one.

Maybe someone else has a better idea.

Could be a short in the ignition switch or ECM.....does the fan run normally with the car running? in all speeds? can you shut it off with the car running?

https://www.youtube.com/watch?v=6YiCjnjLKH8

I didn't ask that, but will.

I'm only involved in this via a telephone. She calls me at 7PM on a Thursday wanting to know what to do, and I'm 30 miles away and have never worked on a Pontiac, and the last time I touched a car to work on it was 15 years ago, when I winterized my drag car for the last time. Her brother lives 4 minutes away, and the garage where he works is about 6 minutes away, so he looked into it.

Frankly, brother needs a kick up the ass.....

Asked the question. No, it doesn't always run normal. Now she realizes there are times it won't run at all.

Definitely the relay or connector.

It sort of sounds like the action of a thermal switch. I can see an electric radiator fan behaving this way. It is the heater fan and not the radiator fan?

Definitely not for the engine - that would be "drag strip" action. EVERYONE ran their engine fans between rounds at a bracket race. Walk around the pits on a July afternoon and you heard this weird whirring of a couple dozen fans running full speed.

If it runs for 5 min after shutting it off, I would shut it off 5 min from my destination....or just pull the plug, but that's a judgement call, IE: if she is mechanical....

if she is mechanical....

She is an artist, as well as a nutritionist, but unfortunately much closer to Van Gogh than Da Vinci.

If you or your daughter has access to a 12 volt test light, it should not be too hard to test for the condition. First off, we already know there is power going to the blower motor, and that it has a good ground. The first thing I would do is test to see if there are more than just high speed when the car is turned off. So, run the car, then with the fan on high, turn off the engine and open the door. Some cars use an accessory circuit that allows the accessories to remain on while you are still sitting in the car. The heater-defroster should not be on that relay, but it is worth a check.

Next thing, would be to try changing from high speed to any of the medium speeds. If that lowers the fan, but does not turn it off, then the defroster fan circuit will need to be tested. But, if the fan turns off, I would suspect the high speed fan relay.

I am not sure how or where the relays are located, but if the fan is running, you should be able to remove them one at a time to find out which one is the fan relay. Then substitute another identical relay from another circuit. If the fan will now quit, the relay was sticking. If not, it will require a circuit drawing.

BTW, if it is a sticking relay, there is no sure way to know that it will ever unstick next time. This would kill the charge in the battery. Good luck.

Sounds like a plan to follow to avoid the shop bill.

Her mechanic brother thinks there is a battery tender in the electronics that is shutting down the fan.

That was my initial thought as well. I had a '99 Grand Prix that after several minutes would shut-down most parasitic current draw from the battery. So my thought is that explains the 5 minutes to turn off, I would say that the relay is probably welded so that it is always on and the current shut-off is what is shutting it off after 5 minutes.

Can you turn off the fan while the car is running? Is there an actual off on the HVAC controls, sometimes there isn't on newer cars.

Can you change fan speed with the car running? If so I would doubt that it's a short at the connector as then it would always run at full speed.

Good Luck!

Shawn

Now that's what I wanted to hear - makes sense - front end hit the truck - relay/connector disturbed. We got a very possible solution.

If nothing else bears fruit on this search, a toggle switch wired in series with the blower motor could be used to mask the symptoms if nothing else.

A toggle switch is not a safe solution. Engine fans can draw a lot of juice, 15 amps or more. You'd need a heavy-duty automotive quality toggle switch with a TVS diode across the contacts to protect against inductive kickback. Also, you'd need to keep the switch in the engine compartment as you definitely do not want to bring that much current into the cabin. Don't forget a fuse.

On my car I installed a heavy duty 20A engine fan which eventually blew the fan control module. After I replaced the module I installed a top-of-the-line 40A Omron Automotive Power Relay that can handle a 100A inductive spike to control my new fan off the control module.

It's a helluva setup, car sounds like an airplane with the fan on at a stoplight!

I have some 30A rated ones (mil-spec) in my surplus box. Nice sealed units. My fan circuit has a 30A fuse.

I thought the problem was with the heater/defroster fan, not the radiator cooling fan. Lower amp draw?

A crash can do this to you. Make you aware enough to notice a fan that always worked like this. S.M.

Yeah - that thought entered my mind as well, and her mechanic brother said essentially the same thing, after checking out the strange tire vibration she noticed immediately AFTER the wreck - the vibration that had just started, but was actually caused by cupped tires that had developed over several years.

I think the welded relay contacts are the problem and she just now noticed the problem that had been there for some time.

I think your last paragraph explains it all.

here is a breakdown of fuse block from Alldata for an 08

I assume from that that fuse 32 will be the one to pull. Now, we're talking about a nutritionist and part time artist here - not sure she'll want to try to do this, but we can try. Add to that that we live in a Lake Erie snow belt and soon we'll be waking up to 12" of snow on our car hoods, and 6" more by the end of the work day. I assume this block has been moved to the engine bay like most post 2000 vehicles.

@lonster, that image changes every time I refresh this page. I think AllData does that to prevent hotlinking. Either that or I've been drinking too much coffee.

Alldata does that....kinda sucks when you are trying to help someone.

Is she sure it's the heater/defroster fan, and not the radiator fan? Most cars today have an electric motor to power the radiator fan, and will run even after the engine is shut down. As a matter of fact, most electrically powered radiator fan housings have a warning that the fan may run even if the engine is off.

Another possibility is how the system was wired.

Wife had a 1990 D0dge with A/C. Blower motor would cut out instead of compressor clutch when accelerating or going up a hill.

Well......yeah. It is kind of hard to mistake air circulation in the passenger compartment for a fan running under the hood, unless her firewall is a bit shabbier than I thought it was.