Unique Rear Window Problem

[KelOfTheRockies]

Howdee,

I have read a ton of rear window threads here and don't see my problem, hence the 'unique' reference in the title.

Sometime in the night, the back window rolled itself down and won't come up. Neither the console switch, or the hatch key-switch make it move.

I took the inside panel off and found that if I turn the key toward lock, I can hear the relay inside the hatch ECU click. Same if I have an assistant push the console switch 'up'. No sound from turning either switch to 'down'.

At the motor connector, it has 12v (actually, 11.66) on continuously and the motor is noticeably warmer than the surrounding metal.

Also, when my assistant pushed the console switch 'up', the voltage at the motor goes to zero. With the console switch centered or down, the voltage at the motor is 12v

Anyone have an idea what happened?

Thanks!



- kel

 

[KelOfTheRockies]

Update,
It's getting dark here, so I decided to get out my battery charger and see if I could energize the motor at the connector and at least get the window up (it's also quite cold here now).
Anyway, the window went up just fine. I plugged the motor connector back in and the window did not go down so I thought the movement might have reset some control logic somewhere.
I closed the tailgate. The motor came on and the window went back down.

So, for now, I'm going to crank it up manually with the battery charger and leave the motor unplugged until I can figger out how to fix it. (or some kind folk here can tell me how to fix)

THX!

- k -

 

[SilverRidgeRunner1]

Update,
It's getting dark here, so I decided to get out my battery charger and see if I could energize the motor at the connector and at least get the window up (it's also quite cold here now).
Anyway, the window went up just fine. I plugged the motor connector back in and the window did not go down so I thought the movement might have reset some control logic somewhere.
I closed the tailgate. The motor came on and the window went back down.

So, for now, I'm going to crank it up manually with the battery charger and leave the motor unplugged until I can figger out how to fix it. (or some kind folk here can tell me how to fix)

THX!

- k -

Def sounds like a short to ground could u see any exposed wires connecting to ground anywhere.

 

[KelOfTheRockies]

Def sounds like a short to ground could u see any exposed wires connecting to ground anywhere.

Thanks for the idea. I didn't see anything obvious. The wiring, in general., looks pretty good.

- k -

 

[I_bRAD]

Thanks for the idea. I didn't see anything obvious. The wiring, in general., looks pretty good.

- k -

Have you tested them? I've had wires that look just fine, but were no good.

 

[IBallEngineer]

The rear window motor is supplied power and ground by the Back Door ECU, which in turn gets signals from the switch in the back door, and serial data from the body ecu, which gets a signal from the switch on the dash. The power and ground to the motor are inverted to change direction, up or down. It is highly unlikely the wires in the back door shorted to ground. Unfortunately the most probably cause is going to be the Back door ECU itself, although I guess you could have a switch that is stuck. You could test the functionality of the tailgate key switch, and even the dash mounted switch. If they both test ok, that would leave the body ecu and the back door ecu. I don't know if you can disconnect "just" the serial data wire from the two ecu's, if you disconnect the entire connector you would be taking away power from the back door ecu, so you couldn't really test it, unless you somehow supplied power to Terminals 1,2 and 3 of the back door ECU. Then you could disconnect 1E1 and 1E2 at the body ecu and see if is still going down on its own. If it does, the Rear body ECU is toast.

Of course the easy thing to do is find a known good one to swap in for a test.

 

[KelOfTheRockies]

I believe I just tracked it down to wire problem.

I was on my way to the liquor store to 'officially' quit working on this thing when something I read here popped into my head.

Before heading home, I raised the hatch and felt along in the dark for the cable up at the hinge going from the body to the hatch. As I moved that around to feel through the rubber, I could hear the relay clicking with the movement.

Also, when I was back in the driver seat (drinking being ahead of me in the plan), I pressed the console switch up and down and could hear the relay in the back click both ways - motor is still unplugged. Before, it would only click in the up direction

So, I'll tear into the wires in the light of day, barring any unforseen hangover, and see if I can make it work.

Update later.

Thanks, everybody!

- k -

 

[TheDurk]

As I was reading the thread, I was thinking "liftgate harness." Shorts and opens there are responsible for 65.2% of all liftgate electrical weirdness.

Please post your vehicle info in your sig when you are asking for help, especially year when talking electric. For instance, the bit about serial data posted by [MENTION=102597]IBallEngineer[/MENTION] only applies to 1999 and later. On an earlier model, that fail can easily be a short in the harness. What's your year?

 

[KelOfTheRockies]

As I was reading the thread, I was thinking "liftgate harness." Shorts and opens there are responsible for 65.2% of all liftgate electrical weirdness.

Please post your vehicle info in your sig when you are asking for help, especially year when talking electric. For instance, the bit about serial data posted by [MENTION=102597]IBallEngineer[/MENTION] only applies to 1999 and later. On an earlier model, that fail can easily be a short in the harness. What's your year?

Thanks for the tip. I just created my account yesterday and will get a signature configured soon.

FTR, I have a '96 SR5 Limited.

- k -