Emerson

Hey. I have '97 Grand Cherokee 4.0L I6 and am finding that here in the midst of single-digit temps the blower is running...and draining my battery.

I can open the door and hear it running (when the battery isn't completely dead) even though the outside temp is only 6F.

Is there known issue with sensor units going bad that might cause on/off logic to reverse? It worked during the summer, as designed, but never drained the battery. It's a brand new battery now.

Em

buckshot500

I'll take a shot at this.

Here's what mine does & see if it makes any sense to you.

When I have the HVAC system turned on in my 98 XJ, (even if it is set to heat only) the Air conditioner compressor cycles on and off. When it does this, the electric radiator fan also cycles on and off.

I think the reason for this is that either the AC dries the air to make for better heat, and/or it does this to circulate oil through the refrigerant system.

Either way, I think it is designed to do just that (cycle) and is not the cause of your battery troubles.

This of course is my somewhat mechanically educated guess though, not something that I am sure of.

longship

Could be the blower motor relay gone bad and stuck closed.

Rob

djb383

The a/c compressor should NOT engage in position 4 & 5 on the selector switch. It does engage in all other positions.

longship

I'm slightly puzzled, is the OP saying the fan is running all the time, even with the ignition off. If the fan is running with the engine on, the middle dial needs to be turned all the way counter-clockwise to switch the fan off.

Rob

mdcmn7

if the fan is running when the truck is off, then its the relay. Few bucks at pepboys and a 2 minute fix

Emerson

I suppose I should've been a little clearer and said "sometimes" would hear the blower. I'm kinda with the previous post and buy a new module. I found something on Edmunds that pretty much described the same deal:

http://answers.edmunds.com/question-...ted-58248.aspx

Called the dealership and their price is $160. More than a couple of bucks but cheaper than a dead ride. Will check NAPA/Pep Boys/etc.

Hopefully this solves the problem.

freegdr

we call those blower motor resistors

Emerson

The other part names seems to be more common outside the dealership. Price is about the same. <shrug>

I became a contortionist and attempted to remove the resistor but am having difficulty. I located the front screw (nearest the seat) but can't tell if there's also a rear screw (by the firewall.) Is there? Not the easiest of parts to remove, to be sure. The generic service manual doesn't cover ATC-based systems.

Also inspected the power connector (with red/white wires) and didn't see any indication of melting. The plastic casing is pretty brown but not black. Crud.