Wiper Connundrum

[Robert T]

Got a bit of an odd electrical problem with my zed. My wipers periodically go a bit mental. Wipers work as they should on continuous speed I and II and on intermittent. Pull up at a set of traffic lights with the wipers on continuous and they should drop to intermittent, which mine do most of the time. However, they have now started to wipe repeatedly whilst the car is stopped, but not continuously, more like they stop, then something immediately triggers them to wipe again. They might do this three or four times, then wait for the proper intermittent delay, then do it again two or three times, then wait and so on.

Not long before I noticed this happening, I noticed that the stereo would randomly increase in volume, with no change in speed of the car. On the headunit I have, the speed signal wire (GAL) is connected and I had it set to increase the volume as the car goes faster (essentially as the road noise increases). I have actually turned this feature off now, as it was driving me nuts.

Now it may be a coincidence, but it does seem odd that two things that relate to the vehicle's speed are malfunctioning at the same time. It seems like it is possibly registering false pulses which makes the car 1) appear like is moving when it stopped (the wipers problem) and 2) going faster than it is (the stereo problem).

The speed signal used for these is clearly not the one used to drive the speedo, as the speedo is stable. It may be that it is separate output from the ECU and it may be that is had a bad connection that generates extra pulses when it momentarily breaks connection. The problem is I don't know where it is fed from or where that connection might be.

Has anyone had a similar problem? And did you manage to solve it?

Cheers R.

[pingu]

http://www.porterbility.co.uk/Files/PDF/e36z3_97.pdf

Page 178

Connection 2B

[Southernboy]

Have you checked the fuse and wiper relay functions. Possibly the fuse may have a poor connection, or the wiper relay may be on it's way out..??

[Robert T]

Thanks pingu, from that it is clear that there is one common speed signal and it comes from the instrument cluster. I don't have cruise or an OBC, so I can't check those. The next problem is where the fault lies - I do know I have an intermittent problem with the instrument cluster whereby all the gauges stop working, but as this only happens once in a blue moon, I have been unable to trace the problem as it happens so infrequently, but it does lead me to thinking that it might be a chafed wire leading to the instrument cluster. Having said that, the fault could also be caused by either the wiper module or the stereo themselves or the wiring harness leading to them, causing one to pick up the symptom from the other, so I guess I could try disconnecting them one at a time and see if the fault clears for the other.

On page 175 of the same version of the ETM, I can also see that it is pin 5 of the wiper module that gets the speed signal, so it might be worth my looking more closely at that, as I might be able to disconnect just that and leave the wiper module in place. I will then have working wipers, even if they don't switch to intermittent when I stop. I can then mess about with the stereo.

Barry, I can't see any fuses on the diagram that relate to just the speed signal part. The power to the wipers is fine and not being interrupted, as the wipers operate exactly as they should in intermittent, normal and fast modes. The problem only occurs when the car is stopped and the wipers are on normal, which is when they are supposed to automatically switch to intermittent. If they are on fast or intermittent, they operate correctly, even when the car is stopped.

Cheers R.