Keep Blowing My Hazard Fuse !

[Guest imdtom]

Hi there gents, I'm new to kit cars and also this forum.

i have just bought a robin hood super 7. running a 2.8 v6 granada engine all runs smooth. but i keep blowing fuses on when i turn on hazard lights. indicators work fine just hazards !!!

 

any ideas people ????

[philshelton]

post your location some one may be near and can spare a hour or so to help you also why not join the club and get a list of those near you and what goes on in your area

[Guest carl leonard]

Sounds like bad earth somewhere? Is the hazard switch the Sierra type mounted on top of the steering wheel housing?

 

carl.

[Guest imdtom]

hi carl, the hazard switch is sierra type on top of steering wheel housing.

 

and also lights slash about 3 times then blow... i did have indicator problem but it was 2 doggy connections and a new fuse.

 

so just hazard issue.

[sj-bradley]

What size fuse is blowing? My quick calculation is 4 x 21 watt is 84 watt which would take 7 amps so you'd need a 10 amp fuse.

If it's the same fuse for the indicators and you're using a 5 amp fuse, the indicators would work fine (I.e 3.5 Amps), but the fuse would blow when you use the hazards - hence the 3 flashes and pop

 

Simon.

[Guest robinj66]

Also we need some piccies of your car

[Guest imdtom]

hi all, good news, after reading your posts, i went and had a look and noticed upgraded indicator lights at the front. motor bike i think. which meant 10 amp was no good. done a few calculations and a 20 has solved it. another one of the list......

[sj-bradley]

With regard to upgrading the fuse - Is the cable capable of taking this current? You don't want that to overheat, melt and short circuit as you could be introducing a fire risk. The fuse rating should be less than the cable capacity. I.e 27 amp cable for 20 amp fuse and not the other way around.

 

Out of interest, what size (Wattage) are those front indicators? Sounds like WW2 searchlights

 

Mind you, those indicators only work half the time so the cable could probably take the current for short periods.

 

Do they seem to flash quicker or slower than expected?

 

Simon.

[Guest imdtom]

simon they seem to be fine, plus its hazards so I'm happy with that. only for mot really. indicators and 10 amp fuse works fine. just when all 6 lights flash it pops the 10 amp.

[fry61]

6 x 21watt = 126watt divide by 12volts = 10.5 amp so yes you're just over the limit assuming lamps are truely 21watt & not a little more;then don't forget to add the side repeater load.

[Guest mower man]

So fit a 15 a fuse simples innit mower man

[sj-bradley]

D'Oh - I forgot the repeaters on the edge !

 

Mind, they shouldn't be 21 Watt anyway - I thought they would be ok with 5 Watt and then you'd get 4 x 21W + 10W = 94 W which is just under 8 Amps. I know my repeaters are LEDs so a 10 Amp would be sufficient.

 

You really DO have to check the size of the cable which supplies them though to make sure that its capacity is greater than the fuse rating. After all, you want the fuse to burn out first and NOT the wiring.

 

Also, a 10 Amp rated fuse could probably take up to 15 Amps for a number of seconds before it burns out. Hence the reason that your hazards work briefly and then blow the fuse. You have to look up the time / current characteristics for this.

 

 

For example a BS88 10 Amp fuse can take 12 Amps indefinitely (At least 4 hours) and blows in 1 second at a rated 40 (FORTY) amps.

 

That's why most homes and industry now use circuit breakers and RCDs with trip times of 30 milliseconds.

 

Simon.

[fry61]

Oooppss-- my calc. allowed for a trailer which we sometimes pull.

[Longboarder]

The hazards are repeatedly blowing 10amp fuses yet the three evolutions of sierra switches managed OK on a 10amp fuse. Hazard and indicator supply are separate. I note the indicators did blow a fuse but that has been 'sorted'. What was that 'dodgy connection' about, and was it before/in/after the column switch? Was it linked to the current fault?

I don't think the cause of the blowing fuses has been sufficiently investigated. Does anyone think they know why the fuses are blowing?

Fitting a 20 amp fuse seems like giving a cough lozenge to someone with pneumonia. IMO.

 

Nigel

[sj-bradley]

The only thing left is that there is an insulation fault somewhere.

 

I would try removing ALL the indicator bulbs and fuse and checking the resistance from the bulb side of the fusebox to the chassis.

Swap the leads over and check again (In case of a diode behaviour). It should be very high resistance.

 

I would then pick one bulb, measure it off the car - should be 10 ohms or thereabout and try it in each socket in turn.

 

Don't forget to have the switches on / off to be able to test these at the same time.

 

If you have one socket where the readings are lower than the rest - check that part of the circuit first - all corners where the cable goes etc.

 

Make notes as you go.

 

It could also be a faulty relay.

 

As has already been said - a 10 Amp should be sufficient so you must investigate more closely to find out why the fuses are blowing.

 

Hope that helps,

Simon.