Austin Allegro VDP Keeps Blowing Fuse!!!!

[peasie]

Hi everyone was wondering if anyone can help
I have a 1981 Vanden plas in great condition but the 35amp fuse keeps blowing once inserted,it supplies the horn,interior light,cigarette lighter (if fitted),split brake test switch and warning light (if fitted) and cooling fan motor and relay there are 4 wires either side of this fuse connection on the back of the fuse box.
I was thinking that one of the live wires must be earthing out somewhere causing the fuse to blow am i correct?
Now i know this may be a bit extreme but i was going to cut all 4 lives and reconnect 1 at a time to trace which one is shorting out and what it supplies,then once found i could replace with a fresh length of wire.
Or is there a easier way to trace it?
Any ideas?
Cheers Steve

[Grease Monkey]

Steve, don't cut the wires!, the simplest way is to disconnect everything that that fuse feeds then reconnect one a time and see which blows the fuse. Or if the fuse still blows with everything disconnected you may have a wire that is going to ground, a more difficult fault to trace. Do you have a multimeter? if you have, set to measure resistance and connect the red lead to the accessory side of the fuse box and the black to ground, this will save you using the fuses, the meter will show no resistance if there is a fault, again disconnect each accessory and see when the meter reads infinity, that circuit or accessory is at fault.
Is that clear? not easy to put into words, Neil Campbell covered using a multimeter a couple of issues ago.

John Simpson

[mr rusty]

Don't get to carried away with the wire cutters yet! It's a messy way of doing it as you'll have to rejoin them all again.

Start by disconnecting the things on the circuits, i.e. unplug the hooter, take the bulb out of the courtesy lamp, unplug the fan relay, the fag lighter, etc, and then put the fuse back in: hopefully it won't blow because there won't be any live circuits.

You should then at least be able to narrow the faulty circuit down a bit by replacing one item at a time and seeing if the fuse blows or not.

[TerryG]

My money would be on the horn as they are live with a switched earth so i'd unplug that first.

[JPB]

My money would be on the horn as they are live with a switched earth so i'd unplug that first.

In cases where the horn push is in the wheel, possibly, but the VdP is basically an Allegro and, as such, has a stalk switch that is switched conventionally. Source, Autodata - 1971-1981. This doesn't mean that the horn isn't the problem of course, but just clarifying the wiring...

[TerryG]

My money would be on the horn as they are live with a switched earth so i'd unplug that first.

In cases where the horn push is in the wheel, possibly, but the VdP is basically an Allegro and, as such, has a stalk switch that is switched conventionally. Source, Autodata - 1971-1981. This doesn't mean that the horn isn't the problem of course, but just clarifying the wiring...

ahh, OK. Shows how much I know about allegros

[peasie]

Wow brilliant replies everyone thanks

Going to unplug everything first as you all suggested and take it from there,will keep you all posted
Cheers Steve