Help me diagnose rear wiper motor issues

[eljay]

I think it's best to ask in a separate thread...

Took apart my Avant's hatch trim (a LOT of cursing involved!) to diagnose a rear wiper that is not working. Everything looks very clean under the trim and around the motor, so it doesn't seem like a nasty leak/corrosion issue, although the motor can still be damaged inside, correct?
I checked the wiring and I'm getting 11.7V at the rear connector (on the two outside wires of the four in the plug) when the stalk is on for the rear wiper. Also, when pushing for a spray, I can hear the washer pump under the hood from front driver's side, but I get no spray in the rear. I have even disconnected the hose at the rear wiper motor, but nothing comes out when the pump is going. I don't see any wet spots along headliner to suggest a broken tube. Can anyone point me in the right direction to investigate?

Should I buy a replacement motor since it's not working? What about the sprayer not pulling any fluid to the rear?

Thanks!

p.s. I will be replacing the non-functioning 3rd brake light while I have the hatch apart.

[diagnosticator]

The wiper motor may be burned out, in that case no electric current can flow through the motor armature or field coils, and the motor can't run since there won't be an electromagnetic field in the motor windings if the winding coils are open circuit or shorted to the motor frame. The motor can be tested with an Ohm meter to check for the correct resistance of the field and armature windings, and for short circuits to the motor frame.

The power supply circuit could have excess resistance due to a bad connection somewhere, with a lot of voltage drop to the motor when the motor is pulling a lot of current.

The ground circuit connecting the negative polarity of the power supply from the motor and or hatch lid to the chassis body could be high resistance aka open circuit, no continuity with a bad connection in the brown ground wire circuit, typically at the points of connection to the body sheet metal.

[MacFady]

Took apart my Avant's hatch trim (a LOT of cursing involved!) ...

Not sure if you saw this (scroll halfway down) but it helped me in the past to get the trim off and know where the attachment clips were located. I'm guessing you didn't have the VAG tool 3370 at your disposal, but fashioning one yourself I found very helpfull to release the top clips. Any type of low profile hook you can make out of metal will help. I recommend starting at the top when putting it back together as well.

[eljay]

Not sure if you saw this (scroll halfway down) but it helped me in the past to get the trim off and know where the attachment clips were located. I'm guessing you didn't have the VAG tool 3370 at your disposal, but fashioning one yourself I found very helpfull to release the top clips. Any type of low profile hook you can make out of metal will help. I recommend starting at the top when putting it back together as well.

Thank you. I have actually used this DIY instead, although I saw the one you linked to as well. Even with clear instructions, it was a PITA job to unsnap those spring clips.

[eljay]

The wiper motor may be burned out, in that case no electric current can flow through the motor armature or field coils, and the motor can't run since there won't be an electromagnetic field in the motor windings if the winding coils are open circuit or shorted to the motor frame. The motor can be tested with an Ohm meter to check for the correct resistance of the field and armature windings, and for short circuits to the motor frame.

The power supply circuit could have excess resistance due to a bad connection somewhere, with a lot of voltage drop to the motor when the motor is pulling a lot of current.

The ground circuit connecting the negative polarity of the power supply from the motor and or hatch lid to the chassis body could be high resistance aka open circuit, no continuity with a bad connection in the brown ground wire circuit, typically at the points of connection to the body sheet metal.

Thanks for the info!
I measured the resistance between the connections on the plug on the motor itself:
Brown (ground) to black/yellow - 1.23 ohms
Brown to black/purple - 3.84 ohms
Brown to blue - 2.67 ohms

Are those readings too low?

Also, how does the sprayer work? Shouldn't I be getting fluid shooting from the tube even if the motor is not turning the wiper? Or does the motor play a role in pulling the fluid as well?

Cheers.

[Charles.waite]

There is a pump on the washer reservoir that feeds the rear sprayer so it should work independently of the motor.

[eljay]

There is a pump on the washer reservoir that feeds the rear sprayer so it should work independently of the motor.

That's what I thought. I can hear it running, but no fluid comes out the rear. Will I have to pull the front bumper to see if all tubes are in place and the fluid is being pushed to the rear?