Electrical gremlins - bad earth? UCH functions and foglight affected.

[xena]

I've had an intermittent problem with my UCH for about a year, but it's so intermittent that I'm loathe to spend ~£400 on it in case it is a symptom, not a cause.

It's playing up a lot at the mo (a relay starts chattering, which knocks out the lights, windows, wipers and indicators), but it seems to have co-incided with my car smoking a bit more and the fog light (on the dash) coming on whilst indicating or braking. I'm therefore wondering if it's a bad earth that is causing this.

Although the fog light on the dash is showing up when indicating, it does not actually come on when you're looking at the back of the car. However, if you have the lights on, you can see them dimming to alternate with the indicators flashing.

I looked at a couple of youtube vids on tracking down earth faults, and it said to measure across the battery, then check the earthing points are at the same voltage. They are with the car off, but when the car is running, it's 12.8v across the battery, and 14v from the battery live to the alternator or the engine block.

I'm a bit confused about what to look at next, so would very much appreciate any help. Many thanks x

 

[Harbinger]

Clean the earth lead for the rear lights and check again, it's the left most wire in the block connector, clean it and make the connections tighter, clean the block and try again.

 

[subtle modder]

I have this exact problem, im pretty certain its a burnt out UCH having suffered similar on my new alfa with a burnt out body computer BUT at the same time, having had the UCH out and apart tonight it all seems clean and fine, ive found one track about 5mm long which maybe looks burnt but not bubbled etc

cleaned and tensioned rear light connectors
cleaned rear loom connector by bonnet release handle
cleaned and checked all uch bourd connections
repalced all relays for spare set, same with fuses
cleaned both rear light earths, both front slam panel earths and the gearbox earth strap just to rule that stuff out

anyone else sorted in any other way? gona try one of my spare UCH's in morning which although wont allow me to start car due to coding being different, SHOULD allow me to check if its the UCH and therefore check eveeyrthing else works but im still of the belief im missing something else

Wayne

 

[xena]

I had all the earths checked by an independent Renault specialist, and he confirmed it is the UCH I can just about get away with it at the mo by flexing the board in a certain way but that's a poor fix! I've got another UCH that I'm planning to do exactly the same as you - check if that UCH works ok with just the ignition on. Then there's a bloke local to me who'll swap the immobiliser chip from the bad UCH onto the good UCH for £50, so hopefully that'll sort it...

Really annoying problem tho!!

 

[Zeitgeist0190]

Definitely sounds like the drivers side rear light earth with the fog dash light coming on with the indicators. It was getting bad on mine to the point the mileage would flash etc, literally 2mins to fix, just scraped off some rust on the prong and voila!
If you open the boot, unscrew the drivers side lights, lift away from the car and unclip the connector, looking into the light cluster, the right hand prong is the culprit, use some thin pliara and give it bit of a bend and scrape any corrosion off.
It's possible it's been overlooked, and could save you some money potentially.
As for your chattrry relay - they are up in the passenger footwell, it's easy to knock them out, worth just making sure they're secure!

 

[subtle modder]

Unfortunately or fortunately depending on how you look at it, an hour ago i tried my spare UCH, exact same problems so its clearly NOT the uch, was removed from a good faultless car

Im now thinking interior loom oddness for the night lastnight is the sidelights not using a relay on the UCH?

Will go have another look at the drivers rear light, got to say it looked clean and had good multimeter readings the other day though..

Thanks for all help

Wayne

 

[subtle modder]

The other odd part, a year ago when the car was last on the road, the central and remote locking worked, now neither does, the chip in the key has died so its got a pep in it to bypass the key but cental locking from key still doesnt, relay set from a good 182 used so again dont think its a relay fuse problem but of little interest at moment :-/

 

[subtle modder]

Just found out the alternator is seemingly dud, 12.43v standstill, running drops to 11.92v rather than the expected 13.5-14v... god knows how that's died from just sitting there but hey.

 

[xena]

My alternator was playing up last year too - I replaced it and it solved the UCH clicking for over 6 months!!! Or it may have been coincidence...

I just tried the spare UCH in mine, and I couldn't get it to do the clicking, so I really do think it is the UCH on mine. Flexing the board slightly stops the clicking, as does pushing the big black square connector away from you slightly, so I think I'm going to try some fancy cable-tie work next.

I'm no-longer sure if the immobiliser chip swap from one board onto the other will work, as despite having the same reference number, the boards are different:

 

[Zeitgeist0190]

Could try goibg over the board with a magnifying glass, see if you can spot any broken paths

 

[xena]

Could try goibg over the board with a magnifying glass, see if you can spot any broken paths

Mmm, no harm in doing that... I think it's a multi-layer PCB tho, so I'd be lucky to find anything, but I'll ask the botanist in work if he has a magnifying glass I can borrow. Thanks!

 

[subtle modder]

Funny you should say that Xena, because while searching alternator problem threads on here last night, a thread came up (which i cant find again) where he replaced his alternator and it solved problems which he thought was a dud UCH, it also amazed me in a couple of threads how common the alts are to go.. odd, ive got a nearly new 182 alt that im gonna put on it, just got to pull it off the scenic first which im loathe to do at the mo.

 

[Timmsy]

May sound stupid but have you checked all the bulbs?

I had almost the same problem... Fog light dash light would come up when braking and then the same with the indicator.. Turned out to be a dud filament in the brake/rear light.

New ones in and all sorted

 

[subtle modder]

New bulbs in all as i keep them in stock for when doing customers yearly services and checkovers, its a real oddity, alt is dead as fook, god knows how its died through lack of use, hoping my new one off scenic hasnt mirracurously died aswell..