Wagon TD Miesters... - PeachParts Mercedes-Benz Forum

Mismost · #1 07-04-2006, 12:39 AM

I'm stumped on the rear wiper and washer motor. I now have 3 motors that I can jump off/hot wire and they run...but they won't run installed in the car.

1. I've removed and cleaned all the switches, tested, they work.

2. put in a different relay, the one in the wagon door, I can hear it click, it is getting juice at least...how would you test it?

3. Cleaned, relubed all the motors, all 3 run smooth and easy when hot wired

4. I can jump wire and squirt the rear washer pump..but again, not in the car

This is starting to sound like a relay....again.

Is there another relay somewhere else on the wagons? There are 2 up under the hood in the black plastic box...what do they do??

Anybody have the MB manual on testing the system?

Any ideas at all??

#2 07-04-2006, 02:27 AM

Quote:

Originally Posted by Mismost

Is there another relay somewhere else on the wagons? There are 2 up under the hood in the black plastic box...what do they do??

Rear wiper wiring diagram.
http://mb.braingears.com/123_DISK2/program/Chassis/82-780.pdf

I'm pretty sure the two relays up front are for the A/C system. (A/C clutch and fan)

Mismost · #3 07-04-2006, 09:19 AM

Thanks Forced! Too bad I read Chinese better than I read these diagrams.

Still, it LOOKS like I could jump/bypass the 5 pin wire off the interval relay and that would tell me if the switch worked and if the relay was bad...you think??

M8, M9...I check those grounds. Don't recall cleaning those on my inital sweep of the car.

#4 07-04-2006, 01:30 PM

I think #2 and #3 are labeled backwards. You might also check the connector above the back door.

Mismost · #5 07-04-2006, 07:19 PM

Good catch on 2&3 being miss labeled...even I should have seen that! Thanks.

Mismost · #6 07-05-2006, 05:21 PM

BUMP...where are you Wagonmasters? Or am I the only one in the world with a bad rear wiper? (Does that make me special??)

Jimmy? Bio300td??

87tdwagen · #7 07-05-2006, 05:52 PM

but you may want to confirm a good ground connection for the switches behind the switch cluster. Seems to be that your signal is not getting from the switches to the pump.

Another possibility could be bad contact within the switch, rare but these are old cars so a possibility. If you have a spare switch tyr that or try jumping the pump and wiper but at the switch harness. If it works at the harness your likely issue is in the switch, replace or try to open and clean contacts.

Hope you find the cause

Mismost · #8 07-06-2006, 12:49 AM

Per the diagram, I found and cleaned up the ground points M8 & M9...no help.

I pulled the relay (#1) out and jumped 3 to 6 at the relay female plug and the motor works! BUT the dash switch does not turn it on or off?? I'm confused as to what this means...bad relay or bad switch?? Looking at the diagram, I don't think it proves anything except the motor works and I knew that!

Fried my brain...too many end of month reports today. Tomorrow I'll try jumping the connection at the switch and find and clean that M2 ground behind the instrument cluster. I don't think it's the M2 ground, but that might fix the stinkin' tach.

JimmyL · #9 07-06-2006, 01:21 AM

Quote:

Originally Posted by Mismost

BUMP...where are you Wagonmasters? Or am I the only one in the world with a bad rear wiper? (Does that make me special??)

Jimmy? Bio300td??

Sorry, I haven't been in that area on either wagon. Yes, even the smoker's rear wiper worked.......

winmutt · #10 07-06-2006, 10:55 AM

I have a switch if you need one.

Mismost · #11 07-09-2006, 07:31 PM

I hate electrical stuff! Hate it! Hate it! Hate it! The car is not responding well to hate either.

Pulled the switches, opened up, cleaned contacts, tested, they work.

Had a friend check out both of my interval relays, both check exactly the same. Which according to him means they are either good or they both broken in exactly the same way...which could happen.

Found cleaned up M8, M9, and M2 ground points...one of those is behind the instrutment cluster with grounds about a dozen different things...anyway all shiney and tight now.

Changed out the motor...again.

NADA< ZIP< ZILCH>ZERO nothing changed. Hit the switch, you get a click at the relay, just like before.

The only thing I have not checked is the "8 pin connector over the rear door"...I can't even find it.

I don't even want to talk about the tach, but it is similar.

On a up note! Replacing the fuel return lines was a short, fun, and fullfilling little 15 minutes diverson from electrical hell.

MBeige · #12 07-09-2006, 11:04 PM

If you're missing a relay, check the inside of the wagon's tailgate. It may have fallen inside, as it's installed upside down.

Mismost · #13 07-09-2006, 11:49 PM

Man, I know perzactly where the stinking relay is....one is the hatch door harness, the other one was thrown into the pasture in a fit of rage (glad I got a good Lab, she brought it back).

I did some more testing based on the diagram Forced posted. Grounded the #2 pin, hot to #5 and if I'm reading it right I should have got a lighted tester on some of the other pins...got zip. In fact I could not even make it click the relay, but it will click in the harness??

I sure would like to plug these 2 relays into a working system...at least then I'd know if they are both good or both crap! Any wagons in South Texas??

JimmyL · #14 07-09-2006, 11:52 PM

Quote:

Originally Posted by Mismost

Any wagons in South Texas??

I imagine several will be fairly close on sept 29...

Palangi · #15 07-09-2006, 11:57 PM

Son, you gonna be two months late.