Blower Plug for A/C Repeatedly "Acting Up"

[Doctor W]

On my 97 ZG Limited with the ACC/ATC type A/C system the blower for the A/C stops working on any speed apart from "Max." . When I start investigating I find that unplugging the "variable resistor module" or whatever it's called and re-connecting it gets the blower working again for a few weeks (say 3-4 weeks). I've done this about 4 times now, even cleaning the connection (no sign of corrosion) physically and with CRC aerosol electrical contact cleaner and "tightening" the springiness of the contacts and filling the join with dielectric grease.

However, no matter what "best practice" method I use to connect the plug, the blower just suddenly stops every few weeks........ it's getting really boring and frustrating.......

Any suggestions fellas????

[turbomart]

This is a common fault on wj and wg,s so might also affect zg,s as well.
Check out the thread on blower motor connectors.

[Doctor W]

Originally Posted by turbomart

This is a common fault on wj and wg,s so might also affect zg,s as well.
Check out the thread on blower motor connectors.

Thanks for the reply and link Turbo.... but the motor works fine, blows like hell on max - and noisy as hell on max too!, just doesn't work on the variable speed part of dial switch nor if function switch is put to "Full Auto" (ATC/ACC function).

I know that XJ's with a stepped speed (1,2,3,Max) fan switch are prone to melting the resistor box, but that's a different set up to the ZG LTD's A/C. I've looked at other forums and found nothing like this on any and it's really a bit of a mystery as to why apparently just disconnecting the plug and re-connecting it after going through the motions of cleaning it should make it work again....... I guess ......

It's a Jeep thing, and I DON'T understand!!!

[turbomart]

Sounds like it might be something with the actual control board that the switch and knob is part off. I believe its not supposed to be repairable but id pull it apart and take a look anyway.

[Doctor W]

Originally Posted by turbomart

Sounds like it might be something with the actual control board that the switch and knob is part off. I believe its not supposed to be repairable but id pull it apart and take a look anyway.

You've got the wrong end of the ....wiring....

The plug I'm talking about is the power feed direct to the motor, it sits (a slide-on, clip-on fit) on the motor and the plug has one heavy wire to the motor at one end and at the other side (half) of the plug are many wires (thinner) which I presume come from the fan switch which has "Auto Lo" , "Auto Hi" , and then a continous range from "Lo" to "Hi" via some sort of "black box" or device/s ...........and the blower will ONLY work on "Hi" , at the end of the switch dial.

I assume this is because it makes a DIRECT connection of FULL available power to the blower motor, by-passing any sort of variable resistor/ rheostat type arrangement or it seems from the diagrams the ATC Control Module.

When I "fiddle"/repair it, all I've ever done is disconnect this last plug connection before the motor. So while you'd think the fault could be in the variable resistor/rheostat or ATC Control Module part of the circuit, I never touch that - yet the fault is fixed for another few weeks.

I've been looking at the PDF Service Workshop Manual for ZJ 93-97, Section 8W, pp :116,118,119 - Wiring Diagrams ZJ 75,77,78 and they are not exactly what I have in my car. There is NO connector plug just before the motor, what is shown is the power feed Brown/Red wire going back into a splice with other wires before going into one of the two HVAC 16-way multi-plugs.

So no access to wiring Diagrams for a 97 ZG, however I do have the data and diagrams for the 98 ZG. This shows the single wire going back to the PDC and the several wires going back to the ATC Control Module.This is NOT the same as I have got either!!! Besides which, I never disconnected any other plugs! Looking at and trying to follow different pages on different manuals on different screen pages, going back and forth has resulted in one massive headache!!!!

Again I plea for input and assistance, having explained the problem and its parameters better...... um, I hope.

[Grahame]

I have a similar problem in my JK and it only gets progressively worse. It started out with a few weeks between failures and is now down to a few minutes. From my internet research it is generally one of two faults, the blower resistor or the blower itself. I changed my resistor ($21 from Jeep) and all was good for a day and then it started failing again. When mine fails it doesn't run on any speed but if I turn the car off and wait a few minutes it will work for a short time and then cut out again.

The JK blower motor only has a two wire input and with the testing I've done the motor receives 12 volts on all speeds, so the resistor is varying the current. I took mine for a drive a couple of days ago and let it fail and then I read the voltage at the motor lead without turning the engine off. When mine fails the voltage at the lead is zero so I'm pretty sure the motor is not the problem. When I remove the motor completely from the duct work and connect it, it will run for over 15 minutes without shutting down but when it remount it, it shuts down after a few minutes. So this has got me completely baffled. I thought it might be the vent door which actuates when the fan is turned on but I've checked that and it operates as advertised.

The fact that you have Max blower speed is an indication that your resistor is on the way out and this is not an unknown problem with both JKs and TJs and as Turbomart has said is common on other models. Apparently they die a slow death. I'd be finding out the price of a resistor for your ZG and if relatively cheap, trying that first.

As for mine, it's off to the auto elec.

[Doctor W]

Originally Posted by Grahame

I have a similar problem in my JK and it only gets progressively worse. It started out with a few weeks between failures and is now down to a few minutes. From my internet research it is generally one of two faults, the blower resistor or the blower itself. I changed my resistor ($21 from Jeep) and all was good for a day and then it started failing again. When mine fails it doesn't run on any speed but if I turn the car off and wait a few minutes it will work for a short time and then cut out again.

The JK blower motor only has a two wire input and with the testing I've done the motor receives 12 volts on all speeds, so the resistor is varying the current. I took mine for a drive a couple of days ago and let it fail and then I read the voltage at the motor lead without turning the engine off. When mine fails the voltage at the lead is zero so I'm pretty sure the motor is not the problem. When I remove the motor completely from the duct work and connect it, it will run for over 15 minutes without shutting down but when it remount it, it shuts down after a few minutes. So this has got me completely baffled. I thought it might be the vent door which actuates when the fan is turned on but I've checked that and it operates as advertised.

The fact that you have Max blower speed is an indication that your resistor is on the way out and this is not an unknown problem with both JKs and TJs and as Turbomart has said is common on other models. Apparently they die a slow death. I'd be finding out the price of a resistor for your ZG and if relatively cheap, trying that first.

As for mine, it's off to the auto elec.

On the ZG's HVAC system with ATC/ACC there ISN'T a resistor pack!

The fan operates at an infinitely variable number of speeds. The speed is set by means of the infinitely variable dial when on Manual. When in the Automatic mode it's set by the speed controller "output" of the ATC/ACC module going through either "Lo" (speed) or "Hi" (speed) on the fan speed dial.

So;

On my car at present when set to "Full Auto" on the function dial the fan doesn't blow at all.

The fan doesn't blow when set to "Lo Auto" or "Hi Auto" on the Fan Dial.

The fan will not blow when the Fan Dial is turned through any of the manual speeds except at the very end, at "Max".

If, when the fan is not blowing at any time I disconnect and then re-connect the connector plug to the blower motor I effect a repair so that the whole of the ATC/ACC HVAC Systems work exactly as everything is designed to..... this can last for a few weeks before it stops and I have to run the blower on Maual Max which results in a lot of noise and a very cold very quickly.

I don't think I'm a total idiot novice with motor car electrics but this has got me stumped at this stage.