Can I replace one fuse with a higher rated one?

[postfach]

Now, normally, I would say the answer is no, but here's my situation:

The factory fog light circuit on my car has a 20A fuse.

I've taken out the factory lights (didn't fit anymore due to intercooler piping I stole off my non-facelift Z20) and replaced them with my Hella Micro DE Xenon driving lights.

To save time and keep things tidy, I used the factory fog light wiring - basically cut the connector off the original lamps and joined this to the connectors that plug into the ballasts.

On the loom that came with the Hella set, there was a 15A fuse on each of the 12V feeds to the ballasts. They don't exist in the new circuit.

Can I replace the 20A fuse (which blew almost straight away due to the current draw of the ballasts) with a 30A one (do they even exist? I haven't seen one in any of the cars I've looked in) or do I need to start again using the wiring that came with the lights? (I'd prefer not to do this, if possible)

[Alex B]

You could, but is the wiring up to a 30A load? The simple solution would be to direct wire them to the battery with a 30A fuse, and use the original spot light wiring to flick a relay. Its a bit of a messy way I guess, but should work well and insure no fire.

[postfach]

Yeah that was one of the ideas I had while writing that post. I'd really rather leave it the way it is now, but I am concerned about the wiring catching fire, I don't know what the limitations are for current vs wire size and length. I would assume that the original wiring was designed to have some kind of safety margin but I doubt it would be an extra 50%.

I wonder if the lights would run off 25A... I suspect the current draw is high only for the first few seconds of having the lights on but without installing a larger fuse and watching the current with a multimeter, I can't really think of any way to confirm that.

[Mr.Phreak]

You could, but is the wiring up to a 30A load? The simple solution would be to direct wire them to the battery with a 30A fuse, and use the original spot light wiring to flick a relay. Its a bit of a messy way I guess, but should work well and insure no fire.

+1

[3T-Rona]

what diameter is the wiring approx? id say leave the oem wiring and fit a 30a fuse (green) the initial draw may be high but as they heat up the resistance of the filament will increase so the current draw will lessen.

[postfach]

Fitted a 30A fuse, so far no problems. Borrowed it to test out of my mates car, was in the rear demister circuit, same diameter wiring but longer distance (in his car) so should be ok IMO. I think it was just the inrush killing the 20A one.