Melted fuse ?

[oblertone]

I have a pair of 55w lamps slaved via a switch to my low beam; all has worked well for months until they failed en-route to Achill. I finally got around to pulling the 10A fuse to find that the Red plastic part was distorted by heat, but the fuse ribbon still intact. Replacing the fuse (with another 10A) restored the lights, but left me no wiser as to why the damn things failed in the first place

Any bright (sic) ideas ?

ps - I did notice that they got very hot after being on a longish while, but they are halogen, so i sort of expected that.

 

[Fanum]

If the wiring to and past the fuse holder is under-rated, it might get hot enough to melt the plastic rather than the fuse wire????

My bet though would be that there's a dry (dirty, not complete) connection on the fuse holder though....that could cause enough heat to melt plastic but not burst the fuse wire.

Give it an hour's run them poke your most sensitive parts down there to see if the area's hot..if the wire's rated adequately high, clean the contacts and spade connectors (or replace) and repeat.

Don't go near any large areas of bush whilst it's running hot either

 

[Greg Masters]

I have a pair of 55w lamps slaved via a switch to my low beam;

Paul

Do you mean via a relay or do you mean with a switch in line from the low beam feed?

If the latter, you'd be drawing 3 x 55w through the low beam circuit. That's almost exactly 10 amps. I'm not surprised the fuse got hot!

If you're using a relay, the main supply to the relay can come from an unfused source (like the battery terminal) using a new in-line fuse (10A). The relay-switching circuit (with a separate switch if you like) is fed from the low beam circuit and should add next to nothing to the fuse load. Bill's suggestion may then be correct.

Greg

 

[oblertone]

Relay

Sorry, poor explanation; the relay trigger is fed from the low beam circuit. From what you say I'll have to check out the rating of the fuse holders I used.