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Old 05-23-2019, 09:44 AM   #1 (permalink)
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Window won't roll down.

I have a 1989 45 door Cherokee. The passenger window won't roll down. I'm totally new to doing most electrical work and VERY new to self diagnosing what a problem is, but like a trained monkey I can do some things and remember them for next time.

The window regulator has a yellow and blue wire. The switch sends 12 volts to the motor both up and down. The motor works up and down when plugged into a different door. The following are measurements I've taken while plugged into the passenger door. Blue wire controls Down and the yellow wire controls up from what I gather. Plug means the two wire plug in the door.

Blue Wire, Yellow Wire, Switch pushed UP
1.80V , 6.40v Motor
0 V, 11.79V plug

Blue Wire, Yellow Wire, Switch pushed DOWN
11.79V , 11.77V Motor
11.79V , 0V plug

When I test the plug itself and use a rivet in the door as a ground the Yellow wire sends no voltage when the switch is pushed down, only up. As I'd expect. The Blue wire does the same in the opposite direction. Zero volts switch up, 11.79 volts pushed down.

So what I see that stands out is the Yellow wire is sending voltage to the motor at the same time the blue wire is sending voltage. This probably makes it difficult for the magnets inside the motor to pick a direction to turn.

What am I missing? What should I look for? What is going on here?
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Old 05-27-2019, 10:08 AM   #2 (permalink)
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Is the motor grounded or is it reversing polarity to reverse the motor?

Check the other door and see between blue and yellow you should have 0 v not running, +12vdc in one direction and -12vdc in the opposite. If this is the case then need to review wiring schematic to see where the switching happens, likely in the switch. Can you swap switch from one side to another?
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Old 05-30-2019, 09:37 PM   #3 (permalink)
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Ok motor reverses polarity via the switch. One way one wire should be hot other should be ground. Change direction and they switch. Iíve changed dozens of switches on that vintage cherokee for an inop issue
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Last edited by Brimmstone; 05-30-2019 at 09:39 PM.
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Old 05-31-2019, 07:15 AM   #4 (permalink)
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Changing the switch doesn't make the window work.

Window Switch flipped over: window rolls up, not down.
Door Lock Switch in place of window switch: Window rolls up, not down.
Window switch in door lock: Doors lock and unlock
Door lock switch flipped over in window: Window rolls up not down.

Test switch for conductivity using a multimeter: Switch connections are correct and make connections in the proper up/down direction.

It is currently held in place by one bolt. I've used this bolt as a ground to check voltage.
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Old 06-04-2019, 02:16 PM   #5 (permalink)
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I'm not sure about that era of cherokee, but on the later ones (and my '99) the wires running from the door to the body get brittle and break. You can show full voltage even if one strand is still connected, but it won't carry enough amperage to operate the motor.

So you might want to unwrap the bundle running from the doors and look for any that looked cracked.
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Old 10-12-2019, 06:45 AM   #6 (permalink)
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I changed it the driver side switch panel and the window works now.
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