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Discussion Starter · #1 ·
97 ZJ 5.2 with manual temp controls

Right after Thanksgiving, I went out to start the ZJ and the battery was dead. I charged that battery and the next morning, drove the ZJ to church. When I came out, the battery was dead again. Took that battery home, charged it and put it back in. Only this time, I noticed that the blower motor was running with the ZJ off. I did a search on NACGA and found that the blower resistor can short out to ground causing the blower motor to run all the time. I put in a new blower motor resistor and all was well....for two weeks.

This morning, when I got back in the ZJ after stopping at the donut shop, I noticed that the blower motor was running on its own again. I just reached down and unplugged the blower motor resistor and it shut off. I'm hesitant to believe that the resistor has failed again. I'm leaning towards something else causing with a path to ground that is causing the issue. Has anyone had a similar problem? Any ideas on what else to check? Could the blower motor itself be the issue?
 

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Discussion Starter · #3 ·
From the FSM:

"On models with the standard manual temperature control system, the
blower motor speed is controlled by regulating the battery feed
through the blower motor switch and the blower motor resistor."

AND

"The resistor has multiple resistor wires, each of which will reduce
the current flow to the blower motor to change the blower motor speed
by changing the resistance in the blower motor ground path. The
blower motor switch directs the ground path through the correct
resistor wire to obtain the selected speed.

With the blower motor switch in the lowest speed position, the ground
path for the motor is applied through all of the resistor wires.
Each higher speed selected with the blower motor switch applies the
blower motor ground path through fewer of the resistor wires,
increasing the blower motor speed. When the blower motor switch is
in the highest speed position, the blower motor resistor is bypassed
and the blower motor receives a direct path to ground."

Based on that, I don't think the resistor is the problem. All 4
speeds work. Something has to be delivering power to the motor while
the key is off in order for the motor to be running. Even with the
AC/heat contol in the OFF position, there is still a drain on the
battery.

I have looked at the wiring diagram (for a 98, not 97) and I can't
find a relay in the system. According to the 97 owner's manual,
there is a 40A fuse in the PDC for the 'Blower Motor & High Speed
Blower Motor Relay'. I would think if that were bad that the blower
wouldn't work at all. I'm going to try swapping it with another 40A
fuse at lunch. If that doesn't do it, I'm wondering if the switch
might not be bad. I'm not looking forward to troubleshooting this
one...
 

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Discussion Starter · #4 ·
More info:

I read on http://www.wjjeeps.com/blower_motor.htm that a faulty ignition switch could be causing the blower motor to run.

6. IGNITION SWITCH: Some models use the ignition switch to engage the blower motor relay. Defective ignition switch may allow the blower motor to operate with the ignition off. Check ignition switch operation and related circuit wiring to blower motor relay.

When I went to lunch, I plugged the blower resistor back in and paid close attention to the ignition switch. I can now make the blower motor stay on with the ignition switch. When it stays on, if I turn the ignition switch from OFF just slightly towards ON, the blower motor will go off. So now I'm thinking that the ignition switch is where the issue lies. Another sign is that the airbag light is staying on at the same time.
 

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Auto Temp

More than likely the blower speed control module is bad. Located by the blower motor.
Auto air doesn't use a conventional resistor.
 

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the speed control module is $$$$ 200 from the dealer so make sure that this is what it is. i have one of these that is brand new. if you are interested.
 

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Discussion Starter · #7 ·
It has manual temp control, not auto. The resistor was replaced two weeks ago.
 

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Blower Prob

My bad, don't know where I came up with you having auto ac.
 

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97 ZJ 5.2 with manual temp controls

Right after Thanksgiving, I went out to start the ZJ and the battery was dead. I charged that battery and the next morning, drove the ZJ to church. When I came out, the battery was dead again. Took that battery home, charged it and put it back in. Only this time, I noticed that the blower motor was running with the ZJ off. I did a search on NACGA and found that the blower resistor can short out to ground causing the blower motor to run all the time. I put in a new blower motor resistor and all was well....for two weeks.

This morning, when I got back in the ZJ after stopping at the donut shop, I noticed that the blower motor was running on its own again. I just reached down and unplugged the blower motor resistor and it shut off. I'm hesitant to believe that the resistor has failed again. I'm leaning towards something else causing with a path to ground that is causing the issue. Has anyone had a similar problem? Any ideas on what else to check? Could the blower motor itself be the issue?

Hi, How are you, I see that this publication is VERY old, but today in 2021 I have encountered exactly the same problem that you raise in this forum. I have read the comments, but I see that they have not published any useful solutions. Have you finally been able to solve this problem? The solution to this would be of immense use to me!
Thanks!
 
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