Technical Tail light interference problem fix

[panda4president]

Hi All, quick post to share a problem I solved today.

Symptoms:

• Left hand side tail lights went dim when the left indicator or brake light was turned on.
• Double timing on the left indicator.
• When the wipers were on and the left indicator or brake light turned on, the rear wiper was activated :yum:.

The problem:


The problem was a corroded earth pin on the light cluster terminal, and/or a corroded and deformed earth pin on the terminal block on the car.


The first thing I noticed was that the earth pin on the lighting cluster was corroded, and had been heated. I sanded it down to remove the corrosion. Here's a picture of the pins after sanding:

If you look very closely you can see that there is some melted plastic at the base of the earth pin, which indicates that at one point it was heated (probably by the high electrical resistance due to the corrosion).


The head had caused a problem on the terminal block on the car side of the connection.

As you can see from the picture, the earth terminal is not only corroded, but the mating lobes(?) are deformed and wide open, which means they don't squeeze the pin when the connector is plugged in. Here's another picture:

I sanded them down a bit to get rid of the corrosion, and I dug underneath each lobe(?) to bend them back inwards.

I'm afraid I don't have any pictures of the terminal block after the work, but the earth terminal looked a lot more like the rest.

After plugging everything back in, things work again.

 

[panda4president]

By the way, I noticed that several of the flange bolts in the lighting unit are getting a bit rusty - does anyone know where I can get replacement panda fasteners?

 

[koalar]

Well done on you fix.


Thanks for sharing

 

[HannsG]

Yup did the same mate.

Also sprayed WD40 on the connector and it worked wonders.

 

[Wee Smurf]

Same thing done on mine, but used contact cleaner not WD40.

 

[DaveMcT]

High resistance earth contacts are a common fault. When the rear lights do strange things like dimming with the indicators its the first place to look.
Use dielectric grease on the contacts.

 

[irc]

I had to splice a new connector in for a friend's Panda as their connector had melted enough for the pin to move. No amount of tweaking and bending would get it to make a reliable connection. Wasn't able to find a new connector so recycled one from my spares car. Bizarrely the colours were different despite being same model & year.

Certainly worth cleaning up the connectors once in a while to avoid problems, and definitely at first sign of symptoms.

 

[Baby Panda]

Re: Tail lights flickering when indicating or braking

High resistance earth contacts are a common fault. When the rear lights do strange things like dimming with the indicators its the first place to look.
Use dielectric grease on the contacts.

Had a similar problem with our offside tail lights flickering when either indicating or breaking. Looked in the Haynes manual for clues, but nothing.:bang:

Checked here and found earthing fault was a common reason.

Found the culprit, the earthing screw in the boot had gone rusty. Replaced it with a new screw and all OK now.
Thanks for the information.

 

[DaveMcT]

Most fasteners are standard M6 or M8, though some will be high tensile just think what they are expected to do before using any old bolt.

Fiat will have them but check prices. Always go OEM for anything special like suspension fasteners.

There are many eBay sellers offering all manner stainless fasteners. Carbon steel plated are less common on eBay you just need to tighten down your search string.

Stainless sounds good, but is prone to shaking loose and will often cause electrolytic corrosion when used against ordinary steel (plated or bare metal) and especially so against aluminium. These problems can be managed, but good quality zinc plated fasteners are the better option.

An example https://www.ebay.co.uk/itm/10pcs-M8x25mm-8-8-Grade-Yellow-Zinc-Plated-Hex-Head-Bolt-w-Washer/361556494148?epid=1369152123&hash=item542e724744:g:RSoAAOSw8DJaOngm