Rev counter drops to zero and clock display goes off when I switch on my headlights.....

As soon as I switch on the lights the rev counter drops to zero and the needle does not move even when I press the accelerator. The clock display also just disappears. As soon as I switch off the lights again, the rev counter goes back up to to normal idling speed and the clock dispplay comes back on but has reset itself to midnight (0:00).

Anyone have any ideas where I should start looking?cf_emoticons__BangHead:regards

KP

look on your engine, gear box side, on thr rocker cover there should be a little wire on the rear corner of the engine, its a little eart cable, if thats broken off then the dash lights rev counter etc dont work when lights are on, mate had same problem,

hope helps

aircooled1968 said

look on your engine, gear box side, on thr rocker cover there should be a little wire on the rear corner of the engine, its a little eart cable, if thats broken off then the dash lights rev counter etc dont work when lights are on, mate had same problem,

hope helps

Thats a great help. I've had a look and there is a loose cable down in there - could this be the earth cable?
Got some pics below:


Here the rear of the rocker cover and there is already a black Earth cable going to the ignition coil:




Here is the loose cable:



And here is how it is sitting in the engine. You can see the earth to the coil and the loose cable below to the left :



Where do you think that loose cable should be attached to?

regards

KP

thats the one, look for the nuts holding the side coolant flange on. one of them should be a stud and double nut type thing it goes under the outer nut. or anywhere on the head really will do

Thanks Guys.

I tested the voltage on the cable before securing it and it was reading 3.3 v - will that be right?  I then rested the cable on top off the rocker cover with the engine running and there was no spark so figured it was safe to then bolt it down properly. Cable wasn't long enough to stretch to coolant flange so bolted onto rocker cover along with other earth that goes to ignition coil - Instrument dash all now working a treat.

Bizarre about the 3.3 volts though

coolio, yeah i would have expected 12v from clock but oh well!

My wire goes to the rocker cover and has been like that since new , on a Mk2 golf I had the wire was attached to the coolant flange so guess it's works there as well.

Hi guys,
The rev counter and clock issue has been resolved. however, noticed some really odd stuff going on with dash and lights.

1 - Dash lights are really dim. And only really illuminating above rev counter.
2 - n/s and o/s indicators work as normal. - actually they maybe flash a bit too fast. But when put hazards on, only the o/s flashes.
3 - fuel gauge doesn't seem to be registering any fuel but I know there is fuel in it.
4 - also noticed a spade connector (2 connectors on it) on the gear box with nothing connected to it and on further investigation there are 2 loose cables with spade connectors lying under the coolant reservoir. Should these cables be connected to the gear box?

Regards

ah ok, the flange thing must be a mk2 only thign then.

1. dimmer wheel set to full ya? if so bulbs may just be old/blown and dim

2. hazard switch i would say if they work normally

3. unplug level sender and bridge pins with wire, if gauge goes to full wioring is ok sender needs lookign at. if not check the wiring, the earth for the sender goes to the claw above the fusebox so look for any loose brown wires coming out of the rear wiring loom

4. black and blue/black? if so those are reverse switch wires, they run to a connector on the lighting loom with same colour wires

you will have another 2 pin plug spare with yellow/white and brown thats front fogs, plus if its a later one there will be another with yellow and yellow/black thats dimdip resistor

glad its sorted for you  

rubjonny said

ah ok, the flange thing must be a mk2 only thign then.

1. dimmer wheel set to full ya? if so bulbs may just be old/blown and dim

2. hazard switch i would say if they work normally

3. unplug level sender and bridge pins with wire, if gauge goes to full wioring is ok sender needs lookign at. if not check the wiring, the earth for the sender goes to the claw above the fusebox so look for any loose brown wires coming out of the rear wiring loom

4. black and blue/black? if so those are reverse switch wires, they run to a connector on the lighting loom with same colour wires

you will have another 2 pin plug spare with yellow/white and brown thats front fogs, plus if its a later one there will be another with yellow and yellow/black thats dimdip resistor

1 - yeah dimmer makes very little difference - so guess bulbs have gone? How many are there? and what rating should I buy?

2 - possible, i can check that when i replace the bulbs

3 - still to do.

4 yes black and blue/black - both with blue rubber spade covers - should these plug into that loose connector on the gear box? and are they the reverse lights?

I've also noticed other stuff on the electrics not working - electric windows barely move down and they won't move back up. brake light on dash and seat belt warning light on dash don't work. I'll add some photos of the fuse box below there are hanging loose wires and it doesn't seem to be located in the bracket properly.

Does not fit in bracket:









Red cable lying loose inside centre console:


also loose




More loose:


thanks

KP

with dash lights may be a symptom along with all the other things, poor earthing perhaps.

reverse switch wires yes, they should pop onto the switch and you should be sorted. if the lights come on then switch stuck closed and this is why they were disconnected. if they dont fit the switch the box has been changed at some point you just need to change the switch for the right one

with the fusebox drop it down and jiggle it around till it hooks back in properly, if its been fiddled with before you may need to move the wiring about behind if its too tight

have to trace that red wire could be a few things or not even factory. radio or ciggy lighter perhaps

grey/white wire usually related to rear fog lights, again trace it

red crimp need to expose the wire colour to see if it can be identified

looks liek maybe had an alarm install or something along those lines. check all the brown wires around fusebox area make sure non are hanging loose. you should have a chunky brown coming in with lighting loom, there should be a wire from here to one of the claws above the fusebox plus a wire from the engine loom to here as well. make sure all the earth claws are earthed to each other and the wire from the lighting loom otherwise all the dahs earths will be bad.  you might find 2 of the claws are looped to each other with a brown thats fine, so long as at least one of them is earthed to the lighting loom earth

Hello,

sorry to bring back an old thread but I seem to have the same issue as the OP - when I turn the light on my MFA goes bland and the rev counter drops to zero with the engine running. Turn lights off and the rev counter will work + MFA will have reset to 00:00.

I had a look for the earth on the NS corner of the rocker plate and found one attached (see centre of image).
Would this be the correct earth to check with this issue? It seems firmly attached but it's a bit gunky. Not sure, however, if gunk would prevent it from functioning as an earth?

Or if it's not that one, would it be attached elsewhere?

Not sure what my next steps should be really. Do I remove the earth, tidy it up and refit? Can I check the voltage on it to figure if it's attached to anything or come loose the other end?

I looked in the footwell of the DS briefly but frankly had no idea what I was looking it. The only thing that looked slight off was there was a very thin black wire dangling down loosely, which seemed to come roughly from the direction of the light switch, however, I couldn't even quite tell if it was a wire or just a sleeve.

New to this, so thanks for helping

Yes that’s the right wire, when mine broke it was towards where it joined the loom so maybe follow the wire and check for any breaks.


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No visible damage from what I can see. No idea how to trace it inside the car. Is there any way to test if the wire is working / connected to the switch?
Thanks

Bit confused about this plate on the rocker cover. Literally the only thing that’s attached to it (but I’d removed it in this photo) is that thin earth wire that then joins the loom running inside the car. Should there be something else attached to this plate? Otherwise why bother with the plate and not just mount that thin earth directly to one of the rocked cover bolts?

I can’t see any other loose wires anywhere in the engine bay really. Unfortunately I don’t have a Haynes manual yet so I’m not sure what I’m looking at in the engine bay half the time!

Thanks

There should be a thicker earth lead from the bracket to the bracket of the coil.

If I can get tapatalk to work I'll post a picture….

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Ah thank you!
Def haven’t got that at the moment - could that be the reason for the rev counter issues with lights on then?

Have a read through this, it may help…

View topic: MFA Operating Guide and Econo Gauge - The Mk1 Golf Owners Club