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Chrysler Repair/'99 mini-van:ATC heater front blower motor

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I have a 99 Chrysler van that had sat for about three weeks (don't know that that matters) until I took it in for repairs. The needed repairs required a week and a half of sitting.
When completed, and back on the road, the heater blower motor will not shut off. It has high speed and one speed below that, but when turned to the off position it continues to run. Pulling the blower motor relay and or the fuse in the fuse panel has no affect on it. The only way to turn it off is to get behind the glove box and disconnect it from the harness.
I removed the entire cluster for the heat/air switches and adjustments, and took the switch apart, but nothing in the switch to indicate a problem, and plenty of dielectric grease inside. All the rest of that cluster is electronics, so nothing mechanical there to check out as in the switch itself.
Do you have a clue where or what the problem might be? Maybe in that electronic circuit board?

Answer
Hi Don,
Is this a conventional (4-speed blower) or an automatic temp control unit(many speed blower)? Those have different circuits.
But I wonder that pulling the fuse and even the blower relay doesn't stop it because those are the source of power for the blower motor, and it would be hard to imagine an alternate pathway for current to reach that motor. The speed control of the blower is dependent upon there being a fuse and relay both functional.
Depending upon which type of control unit there is either a blower motor resistor 'block' or a blower motor power module that vary the blower speed, but either way when the speed control is lost or malfunctioning one or the other will be defective. The current from the fuse and relay arrive on a dark blue wire on pin 4 of both those possible devices. But with the fuse and/or relay removed that dark blue wire would be 'cold'.  So check out that wire for whether it shows voltage with the fuse or relay pulled.
The balance of the blower motor circuit simply varies the resistance to ground after the current passes through the motor. But with no power on the dark blue wire the motor should not be able to run. With the automatic temp control unit is it conceivable that an internal short might provide power to the blower motor in which case replacing the power module would solve the problem. It is located where the blower motor wires connect to it behind the glove box.
Also, let me know which type of control you have.
Please see the PS below and respond to it.
Thanks,
Roland

Addendum,
I cannot find the power module, for the blower, on/in my van, that you refereed to in your explanation to me. Where is it located in/on my van?

Hi Don,
It appears from your photos that the blower motor is routed toward the firewall. I don't have the '99 manual, only the '98 and '02. It appears that the ATC was first offered in '99.
My suspicion would be that it is located where the resistor block for the Manual Temp Control unit is located, e.g. behind the engine compartment but along the air intake pathway for the HVAC.
If you lift the hood you will notice that pathway hidden under where the grille at the rear edge of the hood was sitting. To the right of van center there is a rectangular opening and to the right of that is a similar opening but with the outer edge slanted inward. Under that latter opening is where the resistor block is located in a small rectangular opening. The plug for the module is probably attached from the engine compartment side, so you remove the plug. Then the power module probably has 2 screws that hold it in place or if not it may have a spring tang on the narrow side of it that you push in via a screwdriver tip to allow it to pull out forward (at least that is how the resistor block is removed).
This is all surmise on my part, but if indeed the harness for the blower motor appear to go forward and through the firewall that is where I would believe you will find the power module.
The purpose for that location (or the location where it is shown to be in '02 manual) is to keep it cool as it dissipates heat and the electronics could otherwise fail. Somewhere between '99 and '02 both the resistor block and power module were moved to be in the cabin inside the HVAC air flow duct work.
Please take a look and let me know if this is correct.
Roland

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Roland Finston

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Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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