Blowing Fuses

[atwood]

Hi all ....Just spent a couple of hours looking for an electrical problem - no joy.
The 7.5Amp fuse on the tail light/number plate light circuit in my Perentie blows after about 10 minutes. As an auto electrician I make a great bricklayer, but it seems logical to me that the problem must be downstream of the fuse... ie between the fuse and the lights.
Lights and contacts are in good condition, removed plates behind the rear light assemblies, cleaned out a couple of kilos of mud and spread the spaghetti for a good look. Inspected the wiring diagram/s and identified the right wires, all looks OK to me. Difficult to trace from the fuse box, but everything looks OK.
Anyone got any bright ideas?

[Chris078]

There are a couple of places to look. first question - which car ?
GS, FFR????
which fuse box is installed?
glass fuses or blade?

the most likely culprits are
1) remove the airbox and behind it there is a panel that "protects the wiring where it comes through the firewall.
Remove that panel (2 screws) and check the wiring there. what often happens is that the wiring gets jammed between the firewall and the panel and the insulation gets rubbed off.

The other 2 spots are where the harness goes into the chassis at the front and comes out of the chassis at the rear - insutlation gets rubbed off there too.

the other one is where the wiring runs through the rear cross member. it can rub on the bolts holding the pintle in.

[atwood]

Thanks Chris,
GS with blade fuses, wiring in good nick generally, have looked at the rear crossmember and the chassis rail for wiring loom wear - can't find anything.... I will take your suggestion and get in behind the airbox.

[spie]

When mine started doing the same thing it traced back to a short on the number plate light [that only happened when the bulb was in] - Replaced it a couple of weeks ago with an LED one and no issues since

[muddy]

looks like a rust/mud high resistance earth connection

does it have any dull lights?

what is the voltage to earth around suspect circuits?

[bee utey]

Wire a 100W bulb across the fuse holder, this will light up when you find the short. Saves multiple fuses blowing.

[Chris078]

Thanks Chris,
GS with blade fuses, wiring in good nick generally, have looked at the rear crossmember and the chassis rail for wiring loom wear - can't find anything.... I will take your suggestion and get in behind the airbox.

Glad you've got the upgraded blade fuse box.
pull the light off and have a look at it first. might be something loose in there. since getting the airbox off can be a bit of a pest.

[Blknight.aus]

grab a spare headlight bulb adapt it onto a pair of fly leads soldered to an old blown fuse or a pair of male spade connectors.

plug that in in place of the blown fuse and when you find the fault or isolate it out of the circuit the light will go out.

[atwood]

Thanks all...
I have taken tail light assemblies out and have had a thorough look, tracing back wires and harness and looking for shorts. I will remove the number plate light tomorrow and do the same, dunno why I didn't do that yesterday really.
Love the headlamp bulb method, will knock up a couple of spade connectors and I'm sure I have an old sealed beam lying about somewhere.

Don't think there are any dull lights (headlights- but that seems normal... and I will do something about that eventually!), but I did clean out an awful lot of wet mud in my efforts to follow the wires.... after cleaning and inspecting closely, 10 minutes after installing a new fuse and turning side lights on, it made a nice ping noise as it blew. I will also measure the voltage to earth on the offending circuit... Then it's the firewall... will post results when I get a chance.

[camel58]

Don't forget to look in trailer plug wiring .

[BadCo.]

Those rear tail lights are crap and the lamp holders like to loosen themselves and short on the other terminals.