Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Blower Motor Running Without Key In Ignition!

I have a 2002 Mitsubishi Lancer OZ and the problem currently associated with it is that blower motor is running no matter if the key is in the ignition or not. Anyone have any ideas?

There may be a relay that, when the blower contol is set to high, directs current directly from the battery to the blower motor. That was the way my 1978 Oldsmobile Cutlass was wired. If this is the case, you need a new high speed blower relay.

Do you mean cooling fan for the engine?

Many vehicles allow the fan to continue to cool after the vehicle is off. I assume it turns off after a bit, and you may be able to find if this is normal by checking in the manual.

I assumed it was the heater/AC blower. If it is the radiator cooling fan, Barkydog may be right.

How about the radio? Will it play with the key removed too? Is so, the ignition switch is shot. If not, there is a short in the blower hot lead, allowing it to stay hot all the time…

In GM cars there is a blower control module locaed under the dash that controls the blower. When it goes, the blower will run continuously unless you pull the fuse. You’ll need to check the schematic for your car to see what is in that circuit, but the module or relay would be the best guess. In the meantime, pull the fuse.

It is the heater/AC blower. It continues to run with the key out of the ignition.

And I checked the radio as well, that does not appear to work with the key out. This just began happening a couple days ago.

The blower might be controlled by a relay…If it fails, the blower motor could be energized all the time, regardless of key position…

Can you determine at what speed the blower motor is running at?

Because looking at the wiring diagram this could only happen if both the relay and the blower speed switch failed at the same time.


“. . .if both the relay and the blower speed switch failed at the same time”.
I don’t have the wiring diagram, but if the switch energizes the coil in the relay and the relay stuck in the closed position, would it matter if the relay coil was energized? The switch wouldn’t make any difference. I am comparing this to a horn relay. The horn switch can be fine, but the horn will blast away if the horn relah sticks.

Here’s how the circuit works.

30 amp fuse hot all the time first to the contacts of the relay. Fan speed switch has off, which cuts power from the contacts from the fan relay to the resistor module. When the fan switch moves to any speed it energizes the coil in the relay which closes the contacts in the relay.

So the power has to run from the fuse, thru contacts in the relay, thru the speed switch, to the resistor module. So if the contacts in the relay were stuck, turning the fan speed switch to off should cut power to the resistor module.


1 Like

Many Mitsubishis (can’t say with 100% certainty on this model though) use a compressor control module and if that module was acting up it’s possible for the fan to motor on.
Those modules are usually located in the center console area but a wiring schematic would need to be perused before saying that it’s this, that, or the other.

I note that ALLDATA shows a campaign being issued for a cooling fan module replacement but whether that would have an affect on the cabin blower I do not know.
(A campaign is a Recall which has mileage and time limits. Maybe a call to the Mitsubishi dealer could get you a freebie on that issue; dependent on the limits spelled out in the campaign letter.)

1 Like

I agree with Triedaq

I’d guess a stuck relay. I agree with the other, I’d start there. Any qualified auto-electric shop could fix this I expect. You just need someone with a schematic to trace out the blower circuit to see where it is failing.

1 Like

A number of vehicles that have variable speed control for the blower use a sold state speed control module to control the blower speed. The module has continuous power tied to it. When the module fails it can go either open or shorted. In the shorted mode power ties to the blower motor and makes it run regardless of the ignition switch position. You can locate the module by following the wires back from the motor. The module will be mounted to the air ducting for cooling.

I have 2003 lancer , blower is working without key also

So I’m assuming it will b ok as long as I turn switch off right?

If the switch turns the blower off you should be okay but when this type of trouble happens with models using a solid state module to control the blower speed usually you have no control of the blower when the module fails. The blower will either be on all the time or you have no blower at all, depending the failure of the speed control module.

Stop by the dealer’s parts window. Request nicely of the parts guy a copy of the wiring diagram for the heater fan circuit AND the schematic for the same. They’re two different things. If you get them, post them here and it’ll help us to help you. Note that it is not required of the parts guy that he print these for you, so be nice. I’ve had good success with asking for drawings from parts guys.

If anyone here has access to Alldata or Mitchell’s and can (and is willing to) post the schematic, I’m sure it will be greatly appreciated. But I understand if you cannot.