Electrics gone barmy

[Smudger54]

Hi,  I have a Mk1 1998 1.9 TDi Ghia (110ps) and last week the ABS started to occasionally flash on & off. But last night the whole dash went haywire, flashing, air-bag symbol, ABS, Oil warning, the rev dial was bouncing all over the dial. On top of this the wipers stopped and no indicators would work. the car drove fine along with headlights.
So pulled over safely turned off my lights still same problems!! While wondering what to do it all stopped though what a relief before it all started again. Managed to eventually get home but this morning the car wont start with out a boost from the jump starter.
Is this a major electrical fault or possibly a relay/socket issue. I don't want to scrap the car as it's recently had a new clutch fitted last month and is a good runner for it's age.
Cheers

[johnnyroper]

Poss alternator over charging get a meter on battery and see what the output is.
Or an earth has been left loose somewhere?

[daddyfixit]

do the mk1 's have the extra fusebox mounted on top of the battery ??   if so undo the leads, clean with emery paper and try again.

[suffolkadam]

had a friend who had a mk1 Alhambra what done the exact same thing. turned out it was the earth strap under the car ( chassis to gearbox) bolt had come loose once tightened up never had the problem again.

[johnnyroper]

That would make sense having had a clutch recently.

[Smudger54]

Thanks for the replies,
Charged the battery up last night put it in all started no issues except the ABS light, drove 30 miles to work (without any radio or anything else running) and back then checked the battery voltage which had dropped to 12.6v. Put the tester on the alt that's kicking out 13+ so thats fine.
So the weekend i'll jack it up and check the earth strap connection (when I can find where it is  ) and while i'm under there i'm going to check if the ABS sensor was not replaced properly or even if there is a wire break. But would that add to a earthing problem???

[johnnyroper]

If it's charging properly then I would say earth bond problem,if fault re occurs before jacking up run a jump lead from battery earth to engine or gearbox casing see if that stops it.

[Smudger54]

Thanks everyone, went through all the earthing points i could find and loosened them off, cleaned them up applied some copper grease everything is working fine now just need to find the ABS sensor that causing it to stay lit without access to any diagnostics that should be fun 

[johnnyroper]

If you have a multi meter unplug one at a time and measure resistance should have roughly 0.9-1.1k ohms
Also check reluctor rings for signs of damage/rust.
You could even check frequency is generated from each sensor when spinning wheel,obviously frequency changes dependant on speed but if spinning by hand one would assume would turn roughly same speed so expect the reading to be approx the same at each sensor if they are good.
What makes you think it's a sensor causing abs fault?

[Smudger54]

Hi Johnny, The ABS light keeps flickering on and off (dependant on speed) so was going to start at the sensors and work my way back back through the wiring system before getting to a point of paying a garage with a diag system to trace it.

[johnnyroper]

Sounds like it could be sensor related if it's to do with speed.
Check all basics first like wiring condition,sensor gap,ring condition.
Where in south west are you?

[Smudger54]

Bristol

[johnnyroper]

I get over to Bristol a fair bit with work can plug my diagnostic scanner in for you if want?

[Smudger54]

Hi All quick update.

Following the advice from Johnny I checked each sensor spinning wheel with the multimeter attached on millivolts, I was getting readings from all 4 but 2 did seem low 0.7 & 1.1. I rang a ford mechanic who said check for rust/crud buildup around the sensor matting surface, so bit of sanding and retest and the readings gradually increased. I finally got readings of between 1.8 (180) & 2.0 (200) on each sensor. After ensuring that they are not physically going to hit the reluctor ring I then plugged them all back in, started the car and bingo  the ABS light went out after a short drive.
Thanks everyone and also to Johnnyroper for the offer to take time out personally to take a look.