Alarm On, Wipers On Constantly - ECU?
 

R75 Tourer Diesel facelift 54 plate.

I was awoken this (very wet) morning by my car alarm going off - and front and rear wipers going constantly. I managed to stop the alarm but the only way to stop the wipers was to pull the fuse (even with ignition and switch off).

Also, the electric windows don't work, the odometer stays illuminated with ignition off - and the brake lights came on while I was opening the tailgate!

The plenum is well-drained and there's no visible evidence of the ECU having been submerged. Footwells are dry and although the boot gets a bit wet, there is very little water in it.

I have tried disconnecting the battery for over an hour but no joy. The screen washers work as they should. The alarm is behaving now and there are no lock/unlock issues. The windows fuse under the glovebox is intact and each time I replace the wiper fuse, they carry on. Interestingly, they always park properly each time I pull the fuse!

Something else I noticed is that when I was pulling or replacing the wiper fuse, I thought I could hear the ventilation system flaps moving like they do when you turn on the ignition.

Following advice on other posts regarding the K-Bus, I have removed the stereo black box from behind the removable panel on the RHS of the boot. Though there is some water in the bottom of this cavity, the multipin connectors look fine with no evidence of corrosion or of having been wet.

I have trawled the forums and it seems these symptoms are not uncommon in wet weather, but I can't see where the water has got at mine this time.

Does anyone have any further suggestions or checks I could make?

Many Thanks, Steve

I can't begin to help with any of your main problems, but the wipers parking themselves is probably not unexpected.

Self parking wipers possibly go back to the late 1950's, certainly the 60's.
Their motors, in those days, had an embedded wiper contact, which maintained a 12v supply until they parked.

If of course, this is now also done with electronic wizardry,then OK, it's surprising.

Mike

30-Oct-21

Having now read recent replies, I clearly stand corrected.

Mike

I came across a ZT with similar alarm and wiper symptoms. Turned out to be the clips called snap sacks under the plenum plastic finisher, someone had dislodged them probably during removal of the cover. Once dislodged the water just dripped into the BCU (not a lot of water but enough to gather), was fine once dried out and clip reseated. The seal on the clip snap sacks could of course perish too.

https://rimmerbros.com/Item--i-EYC101450

This is a current post on the site - see the suggested solutions -

https://the75andztclub.co.uk/forum/s...d.php?t=315275

Hello Steve,

I'd begin by soaking up the standing water and removing the "stereo black box" overnight to the airing cupboard to dry out thoroughly. If you open it up, there might be corrosion to the printed circuit boards (I've heard of this before). You obviously have water ingress and that is the most likely reason for the odd behaviour you're experiencing.

Simon

does the car have a sunroof?

Thanks for all your replies.

It gets weirder!

I left the battery disconnected overnight, mainly to avoid it being drained as the digital odometer display remained on at all times (and possibly other things). As suggested I had the stereo black box above a radiator all night and although I removed the screws I could not work out how to separate the casing, so decided to leave it intact.

A friend suggested examining the contents of the engine bay fuse box, removing examining and replacing all the relays, fuses etc. No damp or corrosion.

With the battery reconnected I tried the windows; no joy. I then reconnected the stereo black box in the boot and tested the radio, which worked. BTW the radio is an after market Pioneer App radio incorporating a reversing camera, fitted by the previous owner.

I then noticed that the radio did not turn off when removing the ignition key (it always used to, though maybe a radio default setting after power-down).

Tried the windows again; still no joy.

I fiddled with the ventilation controls and realised that the re-circ button was not working!

Before making a coffee, I decided put the wipers fuse back in, just to see - NO WIPING!! Oooo-errr! Turned on ignition - wipers respond to all stalk controls! Try the windows - THEY WORK!!

...and now the re-circ button works!! Ehh!

The odometer still remains on, as does the radio, but we seem to be getting there.

Do you think it was damp in the stereo black box all along? - or will it remain a mystery for evermore?

Sorry, no it does not have a sunroof.

Hold the euphoria - just looked out and the wipers are going again :duh:

Pulled the wipers fuse. Windows have stopped working again, as has the re-circ button. However, the odometer has gone off with key removal, as has the radio.

Hi Steve,

There's very strong evidence that you have a K-bus fault most likely caused by the water ingress. If you're DIY-minded you can find the main K-bus header above the light switch module to find the guilty part (see "K bus issues", post 15 by MGMarc).

Simon