Out of ideas - Blower issue

So, a purchased a project 2000 XJ. I thought all my issues were mechanical but I found a new one recently. I’ve been troubleshooting but, right now, I’m out of ideas.

When I turn the key to the on position, the blower comes one, even when the blower is turned off at the switch. The fan speed selector does nothing but the blend settings on the switch do seem to work as expected. Here’s what I’ve done to date:

- tested the blower relay - seems to be okay
- pulled the blower HVAC controls and inspected the back - everything looks normal
- unplugged the speed control switch - looks okay but doesn’t change anything
- unplugged the blower resistor - no change
- tested continuity across all pins on the resistor (1 to 2, 2 to 3, etc) - continuity on all pins

What the heck!!! I’m out of ideas. At this point I think it has to be the resistor but it seems to be testing okay (it does look to be original).

Some other items:

I just replaced the steering column (vehicle was a theft recovery).

When I first got the vehicle, the blower worked fine but when I turned it on, the radio would go off. Then, one day, I had the radio on and all of a sudden, the radio went off and now the blower is on constantly. I’ve removed the radio to eliminate that as a contributor.

I’m really hoping one of you guys have some ideas because I’m out of them.

Thanks for the help.


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I mean.... The blower connects through the main harness to the kick panel fuse - from there I would suspect it would go to the hvac controls in the center.
I would get a new HVAC unit or start testing with test leads at that point.

Been doing some more reading. It seems that the center switch (off & blend settings) are vacuum controlled. Could I have an issue where it’s not getting the right vacuum settings to turn off? That wouldn’t explain why the fan speed switch isn’t working though and all the blend settings seem to be working.

I’ve never done anything with vacuum lines before so I’m definitely out of my element.


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If your going to keep this Jeep, I would recommend you p/u a FSM!

I have the service manual. It’s been helpful but hasn’t provided any insight into this issue.


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I already told you what to do.
This is not a vacuum issue....

Jeepburg said:

Could I have an issue where it’s not getting the right vacuum settings to turn off?

Click to expand...

The vacuum is only used to control the blend and routing doors. The fan speed switch is only electrical. You sure someone didn't get creative with the wiring instead of fixing a melted resistor pack? I'd pull the switch and test it with a meter.

@lawsoncl - Good info on the vacuum lines. I wasn’t sure exactly how the “off” setting worked on the blend switch. When I pulled the HVAC controls/radio/glovebox, everything looks unmolested. So I’m thinking that this vehicle didn’t have a lot of science experiments going on.

@blu3fan - When you mention getting a new HVAC unit, are you talking about just the controls in the dash (3 switches/dials)?


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The control unit uses electricity to control the fan. Start troubleshooting using test leads.

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Does the fan still run if you unplug the hvac control from the wiring harness?

@lawsoncl - Yes, if I unplug the fan speed switch and the heater selector (cold/hot), the blower still runs. I have not disconnected the vacuum lines from the blend switch (middle dial)


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Jeepburg said:

I have the service manual. It’s been helpful but hasn’t provided any insight into this issue.


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Click to expand...

You must not have a Chrysler FSM because everything is shown in them! Regarding your issue its in section 8,sub-section 42 and 80.

@RCP - Let me rephrase my earlier comments. I have the Chrysler FSM but I’m struggling to following to wiring schematic (definitely not my strength).

From my perspective, it seems that something has to be energizing the blower relay, even when the switch is off. As I read the schematic, I’m getting tripped up on where the switch is that’s energizing the relay. I’m also not clear on where the resistor fits into that.

Sorry, I’m learning as I go on this one





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The relay becomes hot via the junction block(key in run position) and the blower motor is controlled thru the grounding of the ac/heater control switch via the blower motor resistor.

OK, from what I read, the blower motor is not turning. Do some basic troubleshooting (not just visual inspection). Take a meter and see if there is voltage across the motor when the switch is on. If not, you have an electrical problem. If there is voltage, you have a bad motor.

If there isn't voltage, measure the voltage at the output side of the main blower circuit fuse to ground. There should be. It is very common for a blower motor to seize or short and blow the fuse.

If it is good at the fuse, go over to the speed selector and make sure there is voltage. If that is good, then go over and check voltage on the resistor, all pins.

It is a matter of starting with the last known good voltage (battery) and working your way down to the motor one part at a time.

Jeepburg said:

@lawsoncl - Yes, if I unplug the fan speed switch and the heater selector (cold/hot), the blower still runs.

Click to expand...

Jeepburg said:

When I turn the key to the on position, the blower comes one, even when the blower is turned off at the switch. The fan speed selector does nothing
off. Then, one day, I had the radio on and all of a sudden, the radio went off and now the blower is on constantly. I’ve removed the radio to eliminate that as a contributor.

Click to expand...

old_man said:

OK, from what I read, the blower motor is not turning.

Click to expand...

yes it is.

Can't be the relay or the switch. The relay is there to provide power in the key run position and the switch controls the ground side. My guess it that you have a short to ground between the blower motor and the switch. Start at the resistor pack. If it still runs I bet it's between the resistor and the motor and you've got a wire rubbed through and hitting metal.

The only time the blower motor won't run is if the selector switch is in the "off" position. If it still runs in the off position you've either got a bad switch or some mis-wiring.

A faulty fan motor, faulty resistor, or faulty relay can melt the relay socket and/or wires.