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1996 300tdi dashboard fuse blowing


disco tony
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As title really. My new disco keeps popping the dashboard fuse. I have replace it 3 times and it keeps blowing. It stops speedometer, rev counter and lamps showing and puts the check engine light on. Replace the fuse and all is well again. Where to start? is it worth the bother or should I just go up to a 15 amp?

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As you are aware, it's blown for a reason whatever it is, so imho it would be best to find out for sure, but I wouldn't increase the fuse size.

Could have simply been a faulty fuse, or bad connections at the rear of the alternator or many other things.

Might pay to see if it happens again, before getting too serious.

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No idea about the problem, but as said - dont just put a bigger fuse in. Its blowing for a reason and if you increase the fuse size and the fault is still there then something else has to go - usually wiring.

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No idea about the problem, but as said - dont just put a bigger fuse in. Its blowing for a reason and if you increase the fuse size and the fault is still there then something else has to go - usually wiring.

If we are referring to the 10A fuse 14 which protects the instruments you should also be aware that this fuse also protects the reversing lights.

At a guess I would say there is nothing wrong with the instruments and that your problem lies with the reversing lights circuit ie wiring, reversing switch or the lights themselves.

Have a look at the reversing light bulbs, it's not unknown for a bulb to blow and cause an earth fault . initially just change the bulbs.

The other common fault is the wiring to the reversing light switch, it can rub on the prop shaft and wear the insulation and earth itself on the shaft.

Could even be a faulty reverse switch.

Hope this helps a bit, just don't change the fuse to a bigger rating - good way to set the car on fire.

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Just to re-iterate, never never never replace a fuse with a bigger one if it blows - all you will do is make a bigger mess and ultimately a bigger fire. Find the fault, fix it.

Just remembered the live wire serving the reversing light switch also loops into the speed transducer for the speedo before going on to the reverse lights, i think it is white with green banding.

I have come across this wire being trapped and damaged as it comes out of engine compartment to run under car. In this situation it is easier to disconnect wire in engine compartment and rewire back in new cable.

Hope this helps.

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I have checked the reversing lamps, both ok. Fault is definitely when reverse is engaged, fuse pops straight away. As my disco is auto, I have to pass through R to get to D :wacko: so its going to keep popping. I have had a quick look but cant see reverse switch under car and I dont have any idea where the speed transducer is? Is it most likely the switch anyway?

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I have checked the reversing lamps, both ok. Fault is definitely when reverse is engaged, fuse pops straight away. As my disco is auto, I have to pass through R to get to D :wacko: so its going to keep popping. I have had a quick look but cant see reverse switch under car and I dont have any idea where the speed transducer is? Is it most likely the switch anyway?

Didn't know it was an automatic.

The reverse light switch on an automatic is an integral part of the start inhibiter switch located on left hand side of gear box and is accessible from underneath.

I'm guessing from your description that either the switch is faulty, although you can start the engine, which may suggest it isn't, or there is an earth fault on the reverse light/ speed transducer circuit.

Unfortunately you can't simply disconnect the switch as you wont be able to start the engine.

I think there is only two things you can do, change the switch which may not be faulty or get a test meter out and trace the earth fault.

Hope this is of some use.

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Right then, 5 hours later and a stay in the doghouse for the forseeable, I have found/fixed the problem!!

When I fitted the cb, it went in the overhead console, above the sun visors. When I had that lot dropped, i found a spare connector block. When I belled it out, I found a switched live and what I thouht was earth!! Turned out it was live when in reverse as it was the inhibitor for the optional auto dipping rear view mirror!!!! Half of the headlining down, rear alpine covers out, rear trim panels, rear light clusters.... but eventually traced the bugger back!!

A note for people fitting cb's in the future, the little green wire goes live on reverse!!

Thanks for all your help chaps, now sorted!!

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