where is the fan relay, help on fan circuit

[Ophitoxaemia]

it is wired manually- flip the switch and fan goes on, even if no keys in ignition. then you can turn it on or off when you are driving.

it stopped working suddenly.

there is no power from either side of the switch to ground. the positive wire disappears into the harness and i cant see where it goes.

how is the fan wired? does that positive side go to a relay? what is wired to the relay? what does the relay look like? the negative side appears to go directly to ground. (checked by doing resistance test)

thanks guys, it would take me 10x as long on my own...

james

[Perri]

Looks like yours is wired straight to the switch. Mine is that way now, temporarily. I think I got a relay with the kit, can someone post a pic of it? I don't really see why it is needed.

[2FAST4U]

If you are using the Painless or some other aftermarket wiring harness, the fan relay does not come with the kit. You have to purchase that separately. If you are getting nothing now, the switch maybe be burnt out. The fan draws a lot of current, and the switch really isn't designed to carry that load.

2FAST

[Ophitoxaemia]

ok, that simplies things- and i looked at the build manual which confirms it.

the switch is working- the switch itself it getting no power, so the wire must have been knocked off somewhere.

james

[weendoggy]

You shouldn't run the fan with just the switch handling all the current flow. You should have the switch activate a relay and let the fan run from the relay.

The relay is usually a small box about 1" square. It'll have 4 or 5 terminals on it. One goes straight to battery power. One goes to the fan. One goes to ground. One goes to 12v. switch power.

Depending on how you wire it, you can have the fan activate with the key on or off. You also need to know how the relay works.

The relay will have power in and out, controlled by a small circuit within to activate the switch to close the power circuit. Those will be a ground wire and battery powered one, either straight from the battery or ignition source, but controlled with your toggle switch.

Confused?

If you need a diagram and part numbers to connect a Hella relay, email me.

[Horizon200]

Originally posted by weendoggy:
You shouldn't run the fan with just the switch handling all the current flow. You should have the switch activate a relay and let the fan run from the relay.

For the electrically challenged...why? If I want mine to run continuosly when the key is on, can I not run a ground and then a power lead to a keyed hot wire?

[weendoggy]

Mike,

The main reason is current/amperage draw. Some fans are rated at 15 to 20 amps. That's a lot for a simple toggle switch to handle. Even an ignition switch handling that much current won't survive long. A relay will take the main load of the fan and they are rated at 20amps or better depending on how/what you wire it to, and the wire size you use.

The lead from the ignition to the relay can be small (16ga) because it doesn't carry the load. The relay will have a 10ga. wire for power in and out which will carry the load to the fan (or other electrical item). The electric fuel pump circuit is a good example of what/how it works. It doesn't use ignition current to run the pump, just to activate the relay.

You can wire your fan to work off your ignition switch when you turn on the power, just run it to a relay so it will "activate" and you're set to go.

In other words, the relay acts like a block and tackle system. If you try to accomplish the same load without a block and tackle, it's hard. With it, it's much easier and safer.

[Dior55]

Originally posted by Mike Holt:
</font><blockquote>quote:</font><hr />Originally posted by weendoggy:
You shouldn't run the fan with just the switch handling all the current flow. You should have the switch activate a relay and let the fan run from the relay.

For the electrically challenged...why? If I want mine to run continuosly when the key is on, can I not run a ground and then a power lead to a keyed hot wire? </font>[/QUOTE]Read this thread: http://www.ffcars.com/ubb/ultimatebb...c;f=1;t=023674 It might help you sort it out.

[Roger]

James,

I recall your car being built by a good friend.

Go to the fuse box and locate a blown fuse. Install a 20 amp fuse and you should be good to go.

Roger

[Horizon200]

Got it! Thanks guys!

[Ophitoxaemia]

roger,

you were right on! i am constantly benefiting from ariel's great job building my car!

james