Intermittant wiper control kaput

[jmackro]

A month or so back I wrote a post about a problem with the windshield wipers on my 1970 2800 CS coupe. The wipers would come on at random, run for 4 strokes, and either quit for awhile, or just keep running. The push-pull switch on the column is relatively new and seems to be functioning properly.

The folks on this list informed me that the brown wire from the WW switch is grounded when you pull the stalk back - this energizes the timer that allows the WW motor to run for 4 strokes, as well as the little motor in the cleaner pump. If that brown wire is shorting, to ground it would produce the symptoms I was getting. Made sense.

However, for the life of me, I couldn't find a short. In fact, I rigged up a temporary test bulb to see if the brown wire to the washer pump was intermittantly grounding when the wipers decided to come on. It was not.

In the end I just unplugged the 3 terminal cylindrical relay that I could feel energizing when the stalk was pulled back, and that seems to have solved the problem. Of course it also disables the washer function, but I'd prefer to give that up if it stops my wipers from coming on randomly. The WW still work fine with the "push-pull" knob on the stalk.

The relay I pulled is a Hella 91/56-1-12V "Verzogerungsrelais" (mit un umlat over the "o"). OK, so here's my question: Has anyone ever had one of those go bad before? Can they trigger the wipers by themselves, without the brown wire shorting to ground? Are new ones available?

 

[Honolulu]

Jay...

all these Bosch relays can be disassembled by un-crimping the base. Go to it - you have little to lose. Clean the contacts while you're in there. Then plug it in and fiddle with the wiring harness to activate the wipers.

I don't think the relay is at fault, so it isn't likely you'll see anything improper, but maybe it will prove that the relay is okay and the fault lies elsewhere. I wonder about the wiper switch and whether the terminals on it are not being shorted intermittently by rubbing against something, or a minor bit of conductive crud having sneaked in there.

 

[Bill Riblett]

Take the wiper motor out and take the cover off the "gearbox". Clean out all the 30 year old grease. Check the contacts - if they are corroded, this may be the source of your problems. I've not been able to repair them and have had to replace the whole motor assembly.

 

[Arde]

In the diagrams on this site there is a single changeover relay, and
removing that relay would also disable the wipers. In your case it seems
like there are two relays, and your wipers still work, right?

The fault could be in the relay you removed indeed, or some brief grounding
that triggers it. I tried to use a small bulb to find a short that was blowing
the wiper fuse around 80 mph only, but things happened too fast
to notice on the lamp.

From your description so far the wiper motor and the pump motor are
exonerated.

 

[jmackro]

Arde had written: "it seems like there are two relays, and your wipers still work, right?"

Yes, that's correct. Mine is an EARLY coupe. I bought one of those laminated wiring diagrams that the guy on ebay sells, but the wiper circuit on my car is quite different. The 3 terminal relay that I removed only seems to handle the wipe/wash function - not the general wiper.

Honalulu: The switch on the column was the first thing I suspected. I got a relatively new one from an ebay seller, installed it, and the car behaved EXACTLY the same way. Well, at least the new switch LOOKS nicer! I do like the idea of disassembling my old relay, and determining if there is anything obvious wrong.

Another troubleshooting idea I had: use short lengths of wire with male & female spade lugs crimped onto them to connect the old relay back to its socket; except: I won't connect the brown wire that signals it to kick in. Then if the wipers still come on spontaneously, I know it's something inside the relay, and not a short in the wiring.

Thanks for the ideas.

 

[Arde]

Yep, that debug will tell you what is going on. I may be in the area on Monday in case you need help in prying the relay open...

 

[jmackro]

Well, I tried my debugging idea today, and was able to narrow down the cause to the relay. I connected 2 of the relay's 3 terminals to the socket using lengths of wire with a male spade terminal on one end (that plugged into the socket), and a female at the other (that plugged onto the relay). I left the relay's third terminal - the one that gets grounded when you pull back on the stalk - unconnected.

The random wiper actuation only happens while I am driving, and it takes about 2 minutes after I have started off. Darned if it didn't happen with the relay wired in this diagnostic mode. So, my wiring is not shorting to ground - that #&+^=(* relay has a mind of its own!

I need to take the case off the thing and see how it works. It seems amazing to me that it could actuate with no connection to ground. The two wires connected must be a source of +12 and an output to the load (the ww motor). Another odd thing is that mechanically rapping the relay doesn't trigger it.

Assuming I can't fix my old one, anyone know of a (reasonably priced) source for obscure Hella relays?

 

[jhjacobs]

Jay, I'm having the same trouble. My wipers come on completely at random and initially they wouldn't come on with the stalk switch. It turns out the stalk function didn't work because one of the short black wires was broken. I repaired this and I still get a few random strokes now and then (sometimes a minutes worth but it only seems to happen on odd Thursdays).

I haven't yet been able to capture this gremlin. It does seem like the washer function which activates the wipers; however, if this was the case then the washer pump should also be active and it isn't. I have 3 of the control relays (2 7 pin and 1 6 pin). I swapped it out and the problem didn't really change - now it's more like even Wednesdays.

I don't subscribe much to the corroded contact theory. Generally this will prevent operation rather than causing unwanted operation. However, if there is enough build up of conducting gunk I suppose you could get enough current to trip a relay.

At one point my wipers came on and they stayed on until I pulled over and turn off the ignition. This happened after I had turned them on and then tried turning them off. I was able to repeat this several times before it clear up.

If I figure it out I'll post something about it. Otherwise I'll just enjoy watching the wipers run when they choose to.

 

[BluE9]

All the same symptoms as described in the rest of the thread so:

I replaced the switch and pulled the relay "Hella 91/56-1-12v" with a stamp on top that says "F9".

So now wipers work fine but separately from the washer fluid pump. So when I pull the stalk back I get washer fluid on the windshield then I have to push in the wiper control to clean.

For me, this is not a big deal and I prefer it to the "Crazy Wiper Mode", where they have a mind of there own.

I think it is the relay that is gone haywire.

 

[pmansson]

Replacing the switch

I did this on one car a few years back. Got everything to work the way it´s supposed to.
What I would like to do is transfer the end "handle" part to the new stalk. Why? Because the old one was nice and shiny whereas the new one is a bit rough in the finishing and with a matte surface.
I suppose that they are glued on but haven´t seriously tried to exchange them.
Has anyone done this?

 

[BluE9]

I did this on one car a few years back. Got everything to work the way it´s supposed to.
What I would like to do is transfer the end "handle" part to the new stalk. Why? Because the old one was nice and shiny whereas the new one is a bit rough in the finishing and with a matte surface.
I suppose that they are glued on but haven´t seriously tried to exchange them.
Has anyone done this?

I agree but am happy to leave well enough alone at this point. I saved the nice stalk for the same reason.