Fuse Blowing when Headlight Flasher used

[davgr01]

Hi

1965 3.4 S-Type Auto

Fuse Number 7 operates the Interior Lights, Cigar Lighter and the Headlight Flasher operated from the indicator stalk.

I've had the entire wiring loom replaced by David Marks Garages recently and the flasher worked fine until now.

When I pull the lever to operate the flasher it blows the 35amp fuse.

Could it possibly be the relay?
Where is it located in the engine bay?
Many Thanks
Graeme

[piman]

Hello davgr01,

It's difficult to say as I am not familiar with the S type wiring. However it's unlikely to be the relay particularly as it is likely that is the same relay for the full beam. I think I would first look at the switch to see where the wires run, as the likely problem is a wire touching earth somewhere, (damaged insuation due to abrasion?).
Is it a column or foot dip switch on your car?

Alec

[B87UL]

Graeme

There is no relay in the lighting circuit on a mid 60’s S Type, the only relays are for the Horn and Heated Rear Window.

If memory serves me correctly, operation of the flasher can pull the flasher switch fly lead/ connection at the top of the column, if the harness is a little tight it will result in an earthed contact. I suggest you look at the underside of the switch whilst moving the lever to the flash position.

Did you uprate the headlamps? Is it now possible the fuse is on its limit?

The complete fused wiring system on these cars is rather on its max and some innocent connecting of auxiliary equipment can put the fusing over the edge.

I also think No7 fuse is also a master fuse in series with No1, which feeds main beam. If No1 is intact I would suggest your problem is upstream around the flasher switch, as Alec suggested.

Norman

[davgr01]

Thanks Guys

The operation of the Main Beam is floor mounted and this works fine.

Cheers
Graeme

[piman]

Hello Graeme,

if there is no relay, then it is similar to the Mk 2 and that circuit has the flasher cable connected to the dip switch high beam terminal, if your car does not blow the fuse when on high beam (Your flasher will be live from that high beam up to the switch in that situation), it must be movement of the switch causing an earth fault.
It is unlikely that the fuse is overloaded if the high beam is OK, as that is the same load (Unless you flash while on low beam)

Alec

[470HW]

I had this exact same problem on my MK II. It turned out to be the indicator/headlight flasher. If you look very closely at the internal mechanism you may see that when you operate the flasher it grounds on the housing. This shouldn't happen. When I carefully dismantled mine and inspected it under a magnifying glass I found that a piece of bakerlite insulating material had broken off. I repaired it by bonding some a very small slither of bakerlite onto the protruding alloy. Luckily I took a photo (attached) however, its a photo of my first attempt where I used plastic instead of the second attempt where I used bakelite and did a much neater job. Its worth noting I also had a problem with the bonding until I used a super hard setting epoxy resin. Saved myself a few quid there, its a very expensive part.