No 6 Fuse blowing

[TheDampMan]

Hoping for a little electrical advice.
Every time I drive my car the number 6 fuse blows (radiator fan, Horn Relay, stop lamps, gauges and washer) my first thought was the rad fans so I temporary wired them from a fused feed direct from the battery but the fuse still blows when driving, running the car upto temperature sitting on the drive I cannot get the fuse to blow it only happens when driving.
My thought is a loose connection which shorts out with vibration when driving?

Any thoughts would be greatly appreciated

[Heuer]

Well given in normal driving you would not use the washers and horn, the gauges are operational when the car is idling on the drive I would suspect the stop lamps or their wiring. If you have an area to do it, or can find a quiet time, remove the stop lamps and go for a drive*. Without the lamps the fuse should not blow as there will be no circuit to earth via them.

Other than that it is a an earth short somewhere. Try unplugging the bonnet harness and see if that solves it as there are a lot of connectors in there.


* sounds dangerous but lots of E-Type's go around with no brake lights due to the hydraulic switch being prone to failure.

[cactusman]

If it is a short to earth somewhere I am afraid removing the bulbs will tell you little. If the short is after the brake light switch then the fuse will only fail when you apply the brakes....presuming the hydraulic switch works! It will fail whether or not the bulbs are there. Most likely there is an intermittent short to earth from one of the wires leading from the fuse....green ones....it might be a wire is perished or rubbing somewhere. It might be a faulty load.....bulbs almost never fail short circuit though....I would remove each green side from the fuse and measure its resistant to ground. A few ohms...fine....almost zero ohms not fine. Wiggle wires and see if it suddenly drops to hear zero....it may take some tracing....

[Heuer]

But it is only happening when the car is driven so isolating each circuit might be the way forward. Try removing and isolating each green wire on fuse 6 in turn and going for a drive. The only way you are going to find it is by gradually eliminating each part of the loom so that once found you can then trace it visually. Putting a meter on each is not really going to tell you anything. Isolate, isolate isolate!

[TheDampMan]

Thanks gents yet again great advice from this forum !!

So I isolated each circuit took it for a test drive each time and discovered it’s the indicator circuit that blows the fuse which is surprising as using the indicators when stationary did not blow the fuse?

So my task tomorrow is to find out where the short is, any thoughts on best way to trace this?

[Heuer]

Check the flasher relay - notoriously unreliable with plenty of opportunity to create a short (metal can). I had one go bad and it blew the fuse and stopped the car as I had the Megajolt ignition wired to fuse 6!.

If that is OK unplug the bonnet connector and go for a ride and that will isolate a major part of the loom. It is a bit of a rat's nest in there with several connectors. The big plug and socket also need checking.

[288gto]

Steve,

As David says above and also a long shot, when you took me for a spin a while ago, I noticed there was some movement in either the top part of the column or the stalk switch unit. Could it be shorting out in the switch? I MIGHT have a spare one. I also have a selection of flasher units. More than welcome to call round again and look at mine.

Simon

[cactusman]

It will be a short somewhere....switch, flasher unit or wiring to the lights....and if it only happens when driving it is vibration somewhere so worth jiggling things and see if there is an intermittent short?

[TheDampMan]

Disconnected multi connector to bonnet fuse still blows
Removed indicator rear bulbs fuse still blows
Removed flasher unit fuse ok
Removed the cover from the flasher unit and it appears as new (no rust or any signs of shorting) reconnected switched indicators on jiggled the wires fuse ok
When driving the fuse blows with indicators off or on.
Hi Simon (hope you are well), yes there still is some movement in top of steering column but sitting on the drive turning wheels lock to lock has no effect on fuse.
I think my next step is to check the switch.