Fuse blowing - fuel gauge, temp gauge, indicators (not hazards) full beam (not flashing)

Cornishdefender · Dec 4, 2024

Afternoon
'96 300 TDI Defender 90
Noticed the fuel gauge and temp gauges not working this morning - along with the indicators and full beam. However flashing full beam works and hazards work.
Traced it to the 15amp fuse in the fuse box. Changed the fuse all good and dandy.
Then driving into town, after 3 miles the gauges stopped working again. And on checking, ditto indicators etc.
The fault did not correspond with turning on the sidelights or anything else, was just driving along and the gauges stopped.
Obviously not much point just changing the fuse again - any pointers how to trace what is causing the overload?
Many thanks

miktdish · Dec 4, 2024

Well done for your initial fault finding and identifying the fuse and the circuits.
You deffo have a short somewhere, could be a corroded connection adrift or even a cable rubbing against something else and causing the short.

Logic kinda points me towards looking behind the binnacle first and then at the connections under the drivers seat on top of the tank.

Here's a link to a wiring diagram that i've found useful in the past, hope it helps.

https://duud.ee/LR-manualid/300Tdi_Wiring_Diagrams.pdf

SteveMarquis · Dec 4, 2024

That's brilliant, just the job for my '94 300TDi 90 thanks.

bluedog333 · Dec 4, 2024

Does the fuse blow when you use the indicator?

Cornishdefender · Thursday at 09:05

Thanks for the diagram

Operation Detection is today’s task.
Interestingly the hazards had been working, I used them on the way back once, then went to switch them on again but they stopped working as well
Wondering if the longer screws I used a couple of days ago to refit the angle piece holding the footwell foam up in place might be the culprit….

Cornishdefender · Thursday at 10:21

Correction - screws went in to the ventilator cap below steering wheel…
Am investigating it now - it appears the hazard wiring is the culprit

Cornishdefender · Thursday at 11:17

Usingg a probe to apply 12v to the circuit restores function of gauges, indicators, rear windscreen wiper and washer.
However, if I have an indicator on, then switch on the hazards the indicator stops flashing and hazards don’t work. Switch off the switch and indicator works ok.
It can’t be the screws as have determined there are no wiring looms down there.

Cornishdefender · Thursday at 15:16

With some more investigation this morning my original description of the issue was not quite right. The headlights have always been working so that was erroneus.
So originally the indicators, fuel and temp gauges weren't working - didn't test rear washer/wiper at that time so don't know. At this point the hazards WERE working.
Replaced the 15amp fuse, all good for a couple of miles, then same issue re-occurred for no apparent reason (NAR). Hazards still working though, until they stopped.....
This morning used the probe as per above post - everything that should worked when by-passing the fuse EXCEPT the hazards.
Replaced fuse again, went for test drive, tested all functions except hazards, everything ok for 12 miles (with a stop for a walk in the middle) then original issue happened again (not in conjunction with any activation of switches) and on testing rear wiper/washer that also did not work.
Screenshot is from the wiring diagram kindly posted by miktdish - presumably there is something amiss amongst this lot...
Slightly puzzled as to how the hazards were ever working when the indicators weren't....
OH is an electrician but he admits he hasn't a clue, apart from the absolute basics, about auto-electrics....

Brain for has set in so next attempt to decipher some more will be tomorrow

Cornishdefender · Saturday at 10:27

bluedog333 said:
Does the fuse blow when you use the indicator?

No - that's one of the main problems. There is no immediate reaction to activating any of the switches. The problem just happens after a while of driving.

Dippypud · Saturday at 11:27

Cornishdefender said:
No - that's one of the main problems. There is no immediate reaction to activating any of the switches. The problem just happens after a while of driving.

Check yer earths, back feeding from something maybe be enough to overload the fuse ...

bluedog333 · Saturday at 17:02

Cornishdefender said:
No - that's one of the main problems. There is no immediate reaction to activating any of the switches. The problem just happens after a while of driving.

Ok, as @miktdish suggested earlier it sounds like you have a live short to earth, maybe a chafed wire behind the dash somewhere. The indicator wire (especially NS inner wing) are especially prone to this, but this wire is only live when the indicator switch is on, so you’ll need to be looking at a wire that is always live (with ignition on). So this would suggest one of the gauges as a good starting point!

Cornishdefender · Sunday at 15:25

Good Afternoon - thanks again for the replies and suggestions. After a few hours of tracing wires etc we've managed to cut down the problem area - everything from the connection block on the front bulkhead going to the rear of the vehicle is ok.
The fuse now immediately blows when the indicator is switched to LEFT turn. Fuse is fine when indicator is switched to RIGHT.
We are going to investigate behind the dash tomorrow.
Slightly distracted at the mo given our top barn lost 2/3rds of its roof during Storm Darragh yesterday - 1/3rd went flying into the next door field about 50m....... Our hay is now exposed and we need to try and get it under cover of some sort!

tottot · Sunday at 16:08

Power supply to my place, err not for a while I think.

bluedog333 · Sunday at 18:46

Cornishdefender said:
Good Afternoon - thanks again for the replies and suggestions. After a few hours of tracing wires etc we've managed to cut down the problem area - everything from the connection block on the front bulkhead going to the rear of the vehicle is ok.
The fuse now immediately blows when the indicator is switched to LEFT turn. Fuse is fine when indicator is switched to RIGHT.
We are going to investigate behind the dash tomorrow.
Slightly distracted at the mo given our top barn lost 2/3rds of its roof during Storm Darragh yesterday - 1/3rd went flying into the next door field about 50m....... Our hay is now exposed and we need to try and get it under cover of some sort!

NS wing indicator wire - told ya! Will blow when left turn is activated, it can also blow when wet. I can’t remember off the top of my head, but I think it’s a green wire you’re looking for (check the wiring diagram). It’ll be chafed along the length somewhere (probably about halfway between bulkhead and front indicator).

Fuse blowing - fuel gauge, temp gauge, indicators (not hazards) full beam (not flashing)

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