Fused vs. Unfused Logic

[wings&wheels]

My question; why would certain circuits be unfused? I can maybe see some logic that certain items such as running lights and hazards are critical, but if there is a fault that blows a fuse, not sure being unfused buys you anything but smoke....

I just spent a few days repairing the hazard lights harness on my '72 Rover. The rubbish Tridon flasher I bought a few years ago fell apart and the base w/ the workings fell contacts down on to a metal support. Luckily only the hazard feed took significant damage so that was replaced and some tape took care of the scored spots on adjacent wires....I was very lucky. The hazard circuit is unfused on this vehicle as are a few others; headlights, parking lights, etc. The stop lights are fused. Later Rovers added separate fuses for L & R headlights, side lights, etc.

I added an inline fuse to the hazards BTW. Oh, Lucas jokes along with your thoughts are acceptable, heck encouraged

 

[brianl703]

The only thing I can think of is that those circuits were protected by fusible links which were replaced with regular wire.

 

[wings&wheels]

The only thing I can think of is that those circuits were protected by fusible links which were replaced with regular wire.

I don't think Lucas was that sophisticated

 

[92saturnsl2]

The only thing I can think of is that those circuits were protected by fusible links which were replaced with regular wire.

That's what I am thinking. I would think it'd be very odd/unsafe for relatively high current circuits to be completely unprotected. Fusible links were very common on cars of that era.

 

[wings&wheels]

No fusible links... There are several unprotected circuits on the Rover as well as my TR6, it was a standard practice with the early British auto industries. By the mid 80's that changed.


Here is a related discussion on a UK forum. They speculate on the reasons for not fusing certain circuits, but knowing there are some engineers and experts here, I figured I'd ask.

Unfused Circuits

 

[Trav]

It is common to see old Lucas systems burned right up to the ignition switch especially when someone jumped it negative to ground or installed a aftermarket radio.

 

[wings&wheels]

It is common to see old Lucas systems burned right up to the ignition switch especially when someone jumped it negative to ground or installed a aftermarket radio.

Yes.. One of my regular exercises is also to do a chafing inspection of as much of the harnesses that I can reach, especially the brown, white and red wires on the Brits (brown is ground on the Germans which adds a bit of excitement when switching cars).

 

[jhs914]

Oh, Lucas jokes along with your thoughts are acceptable, heck encouraged

The Prince of Darkness once again proves it deserves the moniker.

 

[jhs914]

You need this:

 

[jhs914]

• Q: Why do the British drink warm beer? A: Because Lucas makes their refrigerators

 

[wings&wheels]

to add perspective:

 

[Trav]

Yes.. One of my regular exercises is also to do a chafing inspection of as much of the harnesses that I can reach, especially the brown, white and red wires on the Brits (brown is ground on the Germans which adds a bit of excitement when switching cars).

I had a Rover SD1 with the 3500 v8 dual SU carbs, the car was great except the rotten electrics. Smoke coming out of one of the rocker switches on the dash or steering column was par for the course. The 65 Lotus Cortina was worse, I didn't think it was possible but it was.
Still, there was something about those cars that I would buy them again and again.

 

[wings&wheels]

I had a Rover SD1 with the 3500 v8 dual SU carbs, the car was great except the rotten electrics. Smoke coming out of one of the rocker switches on the dash or steering column was par for the course. The 65 Lotus Cortina was worse, I didn't think it was possible but it was.
Still, there was something about those cars that I would buy them again and again.

I believe its called an addiction....

I always wanted a Rover 3500S, pretty lines and some of the best hood scoops ever. Survivors are hens teeth, but I will find one someday.

 

[Dave Sherman]

I’ve wondered that myself. My MG’s headlights were not fused originally. I díscovered this when I added relays after my dimmer switch overheated. The previous owner told me the main wiring harness had been replaced after he got into a fender bender that shorted out one of the taillights, where the wiring harness became the fuse. I’m thinking Lucas just wasn’t all that sophisticated since there were only 4 fuses for the whole car.

 

[wings&wheels]

Did I ever mention that most of my old cars have battery cutoffs and aircraft halon extinguishers? Ask me why...

 

[meep]

Did I ever mention that most of my old cars have battery cutoffs and aircraft halon extinguishers? Ask me why...

The world would be +1 1973 VW van had I discovered that tech years ago....

 

[Trav]

I believe its called an addiction....

I always wanted a Rover 3500S, pretty lines and some of the best hood scoops ever. Survivors are hens teeth, but I will find one someday.

That really is a scarce car, I haven't seen one in many years.

 

[atikovi]

That really is a scarce car, I haven't seen one in many years.

You could have mine.

 

[wings&wheels]

You could have mine.

Hi, nice car...not too many of those left here.

I was referring to the earlier 3500/S or P6, one of the best looking sedans ever;

 

[atikovi]

I had a Rover SD1 with the 3500 v8 dual SU carbs, the car was great except the rotten electrics.

I was replying to this post which my car is.