W124 TE rear wiper runs all the time....

[MotardMan]

.....when you switch the front wiper on.

Would you suspect the dash mounted switch for the rear w/w, or the control stalk, or the black box hidden in the tailgate? It only wipes intermittently, as though the dash switch is set to the intermittent position. Which it is not.

Reverse gear engages the ewiper as per normal when the front wipers are on, and the wiper resumes its inter wipe mode when the dar is driven forwards.

BTW, ther front wiper was struggluing across the screen in the heavy Cornish rain last week. I fered the worst and had no access to this forum, or a set of tools to try to fix it. However, I vaguely recalled apost about this problem, and removed the plastic clip on cover from the wiper piston, put some Vaseline on the shafty (ooh-err), and it now works perfectly!

Jim

 

[andy_k]

I'd suspect the switch - it sounds as though it's not disengaging the intermittent wipe contacts.

It's a good place to start, just about the easiest to get at and cheapest component to test/replace. With it out of the car you can ensure everything is working (or not) both on the switch and the car electrics by manually bridging the connections the switch would normally make.

Andy

 

[Mike Buley]

It will be the switch Jim.
Mike.

 

[MotardMan]

Thx to both of you for your replies. I'll try removing the switch and see if this sorts it. I'll order one as well. Thanks guys, appreciated.

Best,

Jim

 

[MotardMan]

Update

I removed the switch for both the inter/constant wipe, and the wash wipe functions last night. Guess what? The darn wiper still runs in inter mode. What on earth is going on here? If the switch was faulty, and I remove it from the circuit, surely the wiper would no longer function? :?

I can here the relay in the tailgate clicking as per normal when the switch is removed, and when it is in the dash. I am at a real loss now as electrics are the one thing I absolutely hate, and do not understand.

Do any of you guys have any idea what I should be looking at now? Nick has offered me a replacement switch, which I am going to buy as a spare in any case, for now I have removed the wiper arm to stop the motor from burning out on a dry screen.

Best,

Jim

 

[andy_k]

interesting one you've got there Jim

I'm going to take a guess that it's a wiring fault - try following the wiring back from the motor unit - see if the casing of it is split anywhere and it's running direct to earth or if it's shorting out behind the switch.

My first priority would be to find out exactly where it's getting it's feed from to make it work and then isolating that. Havbing a wiper that works only when you reverse or on constant with the switch is better than no wiper at all or one that works all the time

Andy

 

[Mike Buley]

hmm, lost me on that one

 

[andy_k]

possibly not quite so confusing Mike :idea: Jim's other post details problems with the heater control for one side of the car - the finger of suspicion is pointing at the control unit in the console - I suspect something is amiss with that.

Andy

 

[Mike Buley]

If the wiring is the same, and connected by location then I reckon you are right Andy.
Fiddling with electrics scares me a bit though.

 

[andy_k]

that control unit is "non serviceable" as far as I know - it's a printed circuit board inside a pretty heavy plastic case. it looks like a case of replace rather than repair.

Electrics don't scare me - they just confuse the hell out of me - why one wire should be the same colour for the full length of the car only to be substituted with another colour by a hidden connector 6" from the object it connects to has always baffled me - it's not just Mercedes that do this but every car I've ever worked on has at least one of these silly anomolies.

Andy

 

[NormanB]

Motard Man
I think you may have an issue with the cable run as it passes through the tailgate - shorting out/picking up stray feed.

I am talking about the harness at the hinge area. There have been posts on this before.

Next time it is doing it open the tailgate and give the harness a massage!

I do not think the rear wiper is routed through the heater control panel at all - although I see you are asking for one - maybe that is for another enquiry you are working on.

 

[MotardMan]

I think you may have an issue with the cable run as it passes through the tailgate - shorting out/picking up stray feed.

I am talking about the harness at the hinge area. There have been posts on this before.

Next time it is doing it open the tailgate and give the harness a massage!

NORMAN, YOU ARE A HERO. HAVE A VIRTUAL BEER ON ME! :lol:

I had a bulb out last night, so up went the tailgate, and inspection of the bulb revealed a sloppy fit in the holder, and lots of milky white deposits. Some wire wool and 10 minutes cleaning and the bulb was fixed. Shut the tailgate, remembered your post and left the car running for 10 minutes. No wiper weirdness!

I even took the car fro drive and the wiper behaved itself this time as well. So now I know where the problem is I can sort it out on a hot summers afternoon.........

Thanks again chaps.

Jim

 

[NormanB]

Good oh

Slurp