Hi,
I have a problem, that never met.:bang:
The Fuse F31 (5A) blows up after 20m of straight driving. And that means no heater, rear light, fog light and others.
After puting new fuse all is OK. If I stand and try all that things everything is OK. But after driving it blows. With the heater turned off.
I've checked allrelays and other fuses - all are ok.

What that can be? What can my car trys to turn on after start driving?:idea:

Thanks for the answers.

PS Fiat Panda 1,2 2008, Robot, Clima.
PPS Sorry for english mistakes, for me it's foreign language.

I thought F31 was the reversing lights??

I thought so too before I met this problem. F31 supplies body computer for all that functions, including rear lights.
I've checked rer light, I also have rear parking system (from previous owner), may be that why there was 15A instead of 5A. But rear light and parking system works propperly before I start driving forward
See attachment for schema.

you need to run a diagnostic on the unit with Multiecuscan or similar - or get fiat to look at it and run the diagnostic.
F31 is a feed to the body computer for initiating a multitude of things.
Hopefully, it is a not a fault in the body computer. It is possible something loose and causing a short circuit when you drive. The body computer is very good at logging faults so may well lead you to the correct point to begin troubleshooting.

edit, sorry sir, I did not see your post - I was also looking at the wiring diagrams whilst typing. - A difficult one - I would go striaght for the diagnostic unit on this one. !

Thanks. I'll try to find someone who can do it.
I've just thought that someone already met such thing.
Hope it's not a problem for new body computer.

I dont think so, It will probably be one of the output circuits... try driving down a very boucy road and see if it blows the fuse faster - that may indicate that it is something loose causing a short circuit. ??
It is interesting though - as the fuse seems to actually protect the body computer internal switching logic.. which is not good if it is blowing as it 'may' mean a problem internally.

Probably more likely - (I just had a thought !) -------
Lean under the drivers side to where the body computer is and pull a few of the connectors (with power off !) have a good look at the connector pins in the plugs - I had an issue the other day with my side light not working and blowing fuses - and logging fatal faults on the BC.. it turned out to be two pins in the lighting connector to the BC were shorting as the plastic had melted !! - had to fit new pins and fix the plug, also replace a cable to the side light - a full run from the socket...
If you see signs of heat on one of the connectors, the pin number on the BC connector should assist in the fault trace.... I would definitely go for that first !.

factory wiring will usually last the life of the car unless its been compomised with a car shunt or it says ford on the badge
you therefore have to assume its the afterfit reversing system causing problems
disconnect at source and see what happens

That is the problem, that I don't know the system causing problem. Any ideas?
And I'm not sure, that "consistent fuse blowing" is a good method. Once it can be not a fuse...
F31 supplies reversing light and some relays. Without that fuse the car thinks that there is no ignition and doesn't switch on these systems. But I can't understand, in normal driving with fog light (blower etc). switched off what can give a short circuit? All relays are switched off. Only the reverse light don't use relay, only the switcher in the gearbox. Where is that switcher?
In the schema there is a block [trip]. What does that means?

captainslarty said:

the BC were shorting as the plastic had melted !!

Click to expand...

All connectors looks normal

Veisatar said:

That is the problem, that I don't know the system causing problem. Any ideas?
And I'm not sure, that "consistent fuse blowing" is a good method. Once it can be not a fuse...
F31 supplies reversing light and some relays. Without that fuse the car thinks that there is no ignition and doesn't switch on these systems. But I can't understand, in normal driving with fog light (blower etc). switched off what can give a short circuit? All relays are switched off. Only the reverse light don't use relay, only the switcher in the gearbox. Where is that switcher?
In the schema there is a block [trip]. What does that means?


All connectors looks normal

Click to expand...

But as we said before my friend, this fuse, on this car, provides power to the body ecu internal switchover circuits - which THEN power other circuits. The reversing light, as you say, and the illumination and control for the air con switch, the cigar lighter illumination, are the only things I can see that use it directly. The Block (trip) is, I believe a thermal fuse unit that will trip in a hard fault - ie, if you replaced a fuse with a piece of wire ..
Again, due to this not being a 'normal' fuse circuit, I would definitely look at the logs of the body ecu as asoon as possible.
You could try removing the reversing light switch, the connector from the cigar lighter (even though it is illumination only) and the main heater blower switch connector, and any associated relays, if it still blows, we may have missed an external circuit, or, it is internal or directly related to the body computer.. about the worse fuse you could have to fault find.

I presume you have completely isolated the aftermarket reverse unit as said above ? - if not do this immediately please. ! - if the owner had wired into that fuse it may well have damaged the wiring around the fuse holder as the wire is only very light. it was never designed for higher current. - have a really good look around the areas the aftermarket unit was added.

Try to look at the back of the fuse holder area if possible for F31 to check wiring there as well ....

I would like to reply for others, because I think I solved the problem.

The problem was in rear lamp. There were self made parking system. And the wires for them went through the hole for light wires. This made a gap in foam-rubber for water that caused are short-circuit in rear lighting.

I found it because later I received the same problem with stop-lighting.

Ok. Thanks all for advices. Maybe this post will help someone later.

thanks for updating,

despite FIAT's "reputation"..,
virtually all electrical issues I've come across are from poorly fitted aftermarket Accessories, :bang:


not changed a fuse OR Bulb in my standard '04 panda :worship:

Charlie