Relays and fuses

[RDJ]

I am hooking up relays for my headlights (one for each headlight) and a small electric fan. Neither of the relays have fuses. Two questions:

1) Do I put the fuse between the starter relay and the relay?

2) The headlight relays are rated for 30 amps, and the fan relay is rated for 16 amps (at least, that is what is printed on the relays). Is this the size fuse I use for each relay? In other words, do I use 30 A fuses for the headlights and a 16 (15 or 20?) for the fan?

 

[FISHBREATH]

RDJ, check down a few threads and you will see one on headlights. Dan has some good advice on using relays. You might want to PM him to address your thread so that we all can learn from the answer. He'll probably see your question before long, however.

 

[67Dart273]

1) Do I put the fuse between the starter relay and the relay?

YES. A fuse/ breaker always goes as close to the source as possible

The headlight relays are rated for 30 amps, do I use 30 A fuses for the headlights ?

I'd say "it depends." If you are only running no14 wire to the headlights, or if the headlights don't draw anywhere near that much (stockers) then use a smaller fuse. I'd take a meter and measure the circuit amperage with the engine running and charging (above fast idle RPM) and see what it draws. You do want a lot of "headroom", though, on fuses for headlights. The LAST thing you want is for a fuse to blow "falsely" when you're tootin' down the dark road. IN FACT I would consider using a breaker instead of a fuse, just like the factory did.

the fan relay is rated for 16 amps (15 or 20?) for the fan?

That must not be much of a fan if it only draws 16 amps. I'd investigate to be sure that the relay is actually only rated at that, and that the fan draws less than that. Once again, what size were are you using to wire this up? Once again, I'd measure the system amperage. Turn the fan on several times, and check if your meter has a "peak hold" function to freeze the surge current. Motors generally draw a lot of current on startup, so if it runs at 16, it may actually need a larger fuse to handle startup current.

Also, mount fuses and breakers AWAY from engine heat. Heat lowers the amp rating on both

 

[POS Dakota]

I am hooking up relays for my headlights (one for each headlight) and a small electric fan. Neither of the relays have fuses. Two questions:

1) Do I put the fuse between the starter relay and the relay?

2) The headlight relays are rated for 30 amps, and the fan relay is rated for 16 amps (at least, that is what is printed on the relays). Is this the size fuse I use for each relay? In other words, do I use 30 A fuses for the headlights and a 16 (15 or 20?) for the fan?

Any fuse should go as close to the source of power as possible.

 

[RDJ]

Thanks for the responses.

But, I guess I am a little slow. What I thought was a relay in the package for my fan switch kit is actually the thermostat. In the description on Summit, it says "relay included: Yes", so looking at the stuff in the bag, I thought it was the relay. Apparently it doesn't come with one? The thermostat kit is a Hayden 3653

http://www.summitracing.com/parts/HDA-3653/

What I have is a 7 blade radiator fan with a schroud, but the fan doesn't really cover the lower left quadrant of the radiator, so I thought I would mount a 10" "pusher" on the front of the radiator on the lower left quadrant. The reason: my car seems to run cool enough, but the weather has been cool. One day a lane was closed, warm day (about 72 degrees), stop and go traffic, and the car got a little hot (about 200 degrees). I have a 25X16 Aluminum 2 core radiator and a 180 degree thermostat. 408 small block, only has about 200 miles on it. Has some problems at 4500/5000 rpms, but that will have to be in another post (otherwise, runs like a champ)

Anyway, the 10" fan pulls 6.7 amps and is rated at 1250 CFM. So, do I need a relay? It doesn't show one in the directions of the thermostat/switch kit. Does the thermostat work as a relay? BTW, I was planning on hooking this up to the starter relay, but should I hook it up to the alternator instead?

 

[67Dart273]

On your mechanical fan, the shroud should cover the complete radiator core. The fan then is "directed" by the shroud, and does not have to

Like I said earlier, a 6-7A fan isn't much of a fan. It might not be worth the trouble.