Technical High level brake connector issue

[dank]

The 'check stop light' warning has been showing on my dashboard for a few days. The only lights that don't appear to be working are within the high level brake light.

I replaced all of them today (with 12v 2.3w bulbs), but the warning light still shows. I did, however, spot this upon removing the connector:

One of them seems to have rusted enough to have broken off? Is it likely that this is the cause of the issue, or should that still be enough for it to function?

Just wondering if it's a good idea to try and source another high level brake before conceding defeat and taking it to a garage.

 

[the green vanper]

Hello,

when you look at the top connector, you can see the part which is not rusted. The bottom connector is rusted far more, so most probably there was some water ingress in the socket. Probably the rusted part is still in the socket, as it just broke. The problem with the rust is that it never stops progressing So even if you'll manage to get it working as is, the rust will go further.

I'd clean the socket of the debris and try to source a new high level brake light (on the photo it doesn't look like dismountable, but they had to put the connectors there somehow...). Try to insulate the socket / plug to prevent water from getting in again.

 

[dank]

Thanks for the reply @the green vanper.

I bought a new light unit and cleared plug of any rust etc. But no luck. I've also checked some of the wiring in the rubber concertina pipe just in case anything has been snagged, but they all look fine to me.

At a loss now as to what else to try.

 

[the green vanper]

Looking at the electric diagram here (I'm checking the first link, which refers to cars made before October 2008):

Home Page

aftersales.fiat.com

If your car is newer, you have to check their dedicated link.

The high level brake light (F040) is connected in parallel with the 'normal' lights (F030/F031) to the body computer (M001). So the problem cannot be before the body computer (ie. brake pedal switch, fuse), but inside or behind it. The left side rear light is using the same earth poing (C030) as the high level light, so it is not the problem with the earth itself (but can be with the earth wire).

Is the light you bought brand new? Or used? If you connect it to 12V, does it work properly?

Do 12V show on the plug when you press the brake pedal?

If the light works correctly, but there's no voltage on the plug, I'd check the wiring. Starting with the earth cable, and then the positive cable up to the pin 18 on the body computer. You can check if there's proper contact on this pin. And then use a micrometer to check for continuity.