Technical Seicento 1.1 has electrical buzzing?

[jm1489]

Hi, my little Sei has an electrical buzzing sound much like the game "operation", which is coming from the rear passenger wheel arch. It happens when I use the foot brake, stationary or moving but not all the time and not in reverse? I thought it was a short making the sound but it is quite loud and constant! Does anyone have any ideas before I take the car a part?

 

[rallycinq]

Does your car have ABS?

D

 

[jm1489]

Not sure if it does have ABS, will have a look tomorrow at some point. So used to these little cars not having much that I didn't think about ABS, though I don't know what would make a buzzing as there would only be a sensor?

 

[jm1489]

OK, traced the buzzing to the rear wiper motor... this now points to a grounding issue in the fuse box. I found that the third brake light wasn't plugged in, reconnected and that light stays on constantly... I assume the previous Owner knew there was a problem? There is some damage to the drivers side windscreen scuttle around the wiper arm and my theory is that moisture has got in behind the fuse box and is causing a short, had a similar problem with my Porsche 944.

 

[portland_bill]

Also check the wiring that passes from the car to the tailgate. This flexes every time the tailgate is opened and closed, and wires fray and break. Quite a problem already on 500s.

As the buzzing is at the rear, that could be where the short is. Peel back the protective gaiter and check the wires carefully. Also check the earth wire from the tailgate, in the side of the boot somewhere, a black wire from the tailgate.
The rear wiper will have a feed all the time when the ignition is on, to power the self-park. If this is shorting to the brake light, it will find an earth path the wrong way down the wire to the fuse box. Disconnecting it removes that path. When you brake, you supply power to the light, which is not earthing through its expected route, and is finding its way into the wiper motor, but with insufficient power to run the motor, hence the buzzing.

If mine, I'd start at the tailgate.

 

[jm1489]

Thanks for info, I don't think the Seicento suffers from cable movement in the hatch as the connection is made using the contacts in lower jam either side of the catch, probably the smartest thing Fiat did? I have a bit of a Christmas tree at the moment... Instrument lights flash with indicators, headlights flash when brake applied etc.. etc.. horn works OK! Still think that the fuse box and local earth is first port of call. Its a pain that there are no dedicated wiring diagrams to show common earthing points or Auto electricians in this part of Lincolnshire.

 

[portland_bill]

Ah, yes the contacts at the door. They can get dirty, but with all the other issues you have the problem is not at the rear.

A particular problem with older Fiats is the main battery cables corrode internally. Especially the earth, from battery to engine and car body. That is where I would go now, before trying all the little connections. (Lots of Panda threads on this)
By-pass the cable with a jump lead.
Check continuity along its length, and ensure that all connections are clean and secure. Possibly just needs a new one.