electrics

[pinky]

 

playing with the electrics I noticed that the white wire from the fuse box goes straight to the distributor then on to the coil

 

could some one explain the reason why this is not fused

is it because the electrics are so variable and would constantly blow the fuse

 

pink

[peejay4A]

I think the theory is that if a fuse in that line was to fail, not because of a fault as such (and they do), the engine would shut down without warning. That could be nasty on a motorway.

[barkerwilliams]

It's the same reason headlights are not fused in TR's. Theory was that a burnt wire is better than all lights out at speed in the inky blackness. (or they just could have fitted a number of separate fuses for main / dip on each side)

 

 

Alan

[Chris1966]

The low tension wire to my coil broke at the joint with the spade connecter last year. I was lucky as I had been on the motorway 10 minutes before, just gone over a bit of a bump in the road and then dead engine followed by smoke as the wire earthed itself before I could turn ignition off. After a bit of pushing I got the car off a busy A road onto a garage forecourt to have a look.

 

I had got a length of wire I was using as a supply to 12v socket and some spade connecters and tools so I made a direct feed to battery to get me the 5 miles home, it had only take out the one wire.

 

It was quite a bit of a scare at the time, but lucky that it happened where it did. So an occasional look at the security of electrical connections is a good idea!

[ianc]

To avoid the problem of all lights out at speed, the Works' Rally TR4s have individual fuses for the 4 filaments in the two headlamps, and separate fusing for the spotlamps. If a car were to hit something rather unforgiving and thereby short-circuit some of the wiring to the headlamps, there was every chance that some of the lamp circuitry would remain operational.

In fact, there are 4 fuseboxes, each holding 4 fuses, and the wiring was implemented by a technician from Lucas who came to the Competitions Department to provide looks custom-made to suit the teams.

Ian Cornish

[Waldi]

I recently ordered a new wiring harness.

For the head lights was I was recommended 2 relais with 2+2 fuses (instead of 4 relais, each with 1 fuse as, I requested). This made perfect sense to me. It will relieve the light switch and main/beam switch, which otherwise have a high probability of failure.

Waldi

[tthomson]

Hi Pinky,

 

The purpose for putting a fuse into a car is to provide a safe point of failure should a device attached to the loom fail, but not for a situation where the loom shorts to the chassis or bodywork. Triumph Standard followed the best advice of the day to only put fuses for auxiliary items. The main circuits are unfused to ensure that there is a connection to the ignition system, the lights and other key parts of the car at all times so that the car does not cut out, or run without lights, from a fuse failure at an inappropriate time.

As mentioned earlier in this thread, You don't really want to be left high and dry for the want of a blown fuse. The downside is that there is always the possibility of a wire burning out. The only way to protect for that is to use circuit breakers, but these were not readily available 50 years ago, and TRs were built to cost.

As Ian C mentioned, for cars that are rallied, because there is an increased risk of wiring shorts from collision damage the loom incorporated a lot more fuses.

 

TT

[Lebro]

A white wire would not normally go to the distributer at all, unless you have electronic ignition, it would normaly go to the coil only.

 

Bob.

[pinky]

 

Thank you for your thoughts on wiring,

I thought as much, however burning out a cable I believe is worse than a fuse going

I have been moving the fuses to spade, as the glass tubes are a problem,break easy,look as if they are ok but are not

I might put an in line fuse in the ignition system but make it a hight rating, this will give it some protection

 

your right of course bob, I will get something right one day

 

thanks pink

[ianc]

In addition to the separate fusing of headlamp filaments (see #5, above), there is a fuse in the feed to the coil from the ignition switch on the Works' TR4s. Probably assumed that an experienced driver would be able to deal with a fuse failure, but the more likely situation in a rally would be a prang causing a short-circuit.

Ian Cornish

[ChrisR-4A]

The low tension wire to my coil broke at the joint with the spade connecter last year. I was lucky as I had been on the motorway 10 minutes before, just gone over a bit of a bump in the road and then dead engine followed by smoke as the wire earthed itself before I could turn ignition off. After a bit of pushing I got the car off a busy A road onto a garage forecourt to have a look.

 

I had got a length of wire I was using as a supply to 12v socket and some spade connecters and tools so I made a direct feed to battery to get me the 5 miles home, it had only take out the one wire.

 

It was quite a bit of a scare at the time, but lucky that it happened where it did. So an occasional look at the security of electrical connections is a good idea!

Was the coil mounted in the original position on the block, if so the wire is flexing all the time the engine is rocking and will eventually break.

Much better to mount the coil on the wing where the wire feed is then fixed and also the coil will run cooler.

Chris