Fuse for relay upgrade

[alan911]

Just did the headlight relay install. Went to the Battery + 12 for power. I'd like to put an in-line fuse on that wire. What amp. should I use ? Will a 25 glass amp fuse work ?

[Tim Walsh]

ALL of my electrics are rated for 30 amps so I put in a 20 amp fuse and that's just fine.

[RoninLB]

a "rule of thumb" that I use is that the circut load should be 70% of the fuse................Ron

[Tim Walsh]

that sounds about right as the lights use up to 16 amps tops. A little high but it's either that or upgrade to 40 amp electronics and I didn't see any of those at radio shack

[RoninLB]

Hey Tim.. I use the 75amp Bosch relay.. it has the screw attachments for the wires and nice big inner contacts.. Bosch # 0-332-002-150...................Ron

[Tim Walsh]

Thanks Ronin. I haven't done my high beams yet but I'll definitly have to use those. Where did you get them?

[RoninLB]

Originally posted by l33t9eek
[BRonin.
Where did you get them? [/B]

Tim... I'm not the greatest financial manager.. so I see them in an FD/PD supply catalog.. Galls Inc., 1-800-477-7766, item# SE057.. they cost me $19.99 each.. somebody who knows what they're doing should be able to get them much cheaper.. it's like a real weather proof relay for under hood FD/PD christmass lights, etc.

[Tim Walsh]

I'll look around for them. Are they DPST relays or SPST relays?

[RoninLB]

single pole.. I use 2 for the lights.. and I will be using one for that hot starter problem.. just to have it hooked up as a back up..beats crawling under the car, when I hit the desert, to screwdriver jump the starter sol.

oh yeah, they measure 1 3/4 X 1 1/2 X 1 1/4in.. I mount them for the lights foreward of the battery on the bulkhead.. just under the lip.. it's a clean install.............Ron

[Randy Webb]

If you have relays in the circuit, then why do you need fuses?

[RoninLB]

Originally posted by Randy Webb
If you have relays in the circuit, then why do you need fuses?

Battery to fuse to relay to lights = 1 circut

[jmohn]

Originally posted by Randy Webb
If you have relays in the circuit, then why do you need fuses?

Because relays do not provide overload protection, they're essentially a switch.

Jerry M
'78 SC

[KTL]

I'd recommend a circuit breaker instead of a fuse.

When you blow a fuse, you need to replace it. When the circuit breaker pops, you reset it.

I used manual reset 25A breakers for my 100W/90W install (12 ga. used for lights & grounds to handle increased load). Like these:

http://order.waytekwire.com/IMAGES/catalog/215_56

And I also got some of the colored boots to protect the poles from accidental contact with something.

Should I have used 30A breakers? 25A will just trip quicker in the event of a problem, no?