Need some help wiring up a relay to some fogs Options

[Jameel]

Finally getting the front end of my '71 looking finished. I mounted up these Cibie and Hella lights and got them wired up today. All went well during testing, but on a drive I blew a fuse, then outright melted another one. Came home to rethink.

I have wired up the J West H4 relays on several 911's, but I have not done it on a 914. I had assumed when wiring this that the round relay in the fuse panel under the dash would be sufficient. It's not apparently!! So, couple questions.

1. I'm running four 55W halogen bulbs, and that works out to 4.58 amps per bulbs, so less than 20 amps total. The Hella bulbs came with a 30 amp relay. Is that relay beefy enough to handle the four 55W bulbs at 20A?

2. If I do wire up this relay, where do I put it? How do I handle the round relay in the fuse panel under the dash?

3. If I switch out all the bulbs for LED's, will the round fuse be all I need?

[Jameel]

I was looking closer at the fuse and whadya know, the metal is intact. What causes the ends to get roasted like this without the wire breaking?

[Spoke]

I was looking closer at the fuse and whadya know, the metal is intact. What causes the ends to get roasted like this without the wire breaking?

You're showing an 8 amp fuse but said earlier you expect the current to be 20A. Did you try a 20A fuse?

Notice the fuse plastic melted on the ends. This means there is quite a bit of resistance between the fuse ends and the metal tabs of the fuse panel. Have you cleaned the fuse ends and panel metal tabs? I recently did this on my 914 using a dremel and wire wheel. Had to be careful not to bend any tabs or break any fuses.


When I say quite a bit of resistance I mean like 0.1 ohm.

Power = I * I * R. Say you have 8amps and 0.1 ohm, that comes out to 8 x 8 x 0.1 = 6.4W! That amount of power dissipation will definitely melt the plastic without blowing the fuse.

If you can't figure out the existing fuse arrangement, Mark's suggestion is a good solution.