Auto Electrical Relay Question

**tips** · 25th September 2008

I need to re-wire a cooling fan that looks like it draws alot of amps. I tested it direct with an in-line fuse (glass type) and the fuse holder got mad hot after a minute or less.

So I am going to wire it with a relay.

For ease of explantion I will associate the pins of the relay with a clock. 12 top 6 bottom etc

So if I have my switched live (from ignition say) to 12, and 6 is ground. I then wire 9 to the positive on the battery with a fuse in line, and then 3 supplies the live from the relay.

If I do it this way, will I still have to up the thickness of the wire on 9 (the fused one as it got hot without the relay) or does the relay alleviate the need to do this?

CHEERS

**MIKE M** · 25th September 2008

give more details ie what car year etc etc coz what you are considering if not done correctly will cause a fire, the vehicle should already have this in place so why not repair it rather than replace

**tips** · 26th September 2008

Hi Mike,

I have just had a reply on another forum that they do run hot and that there isn't a problem with it (I thought there was).

Thanks

**Pegasus** · 27th September 2008

Originally Posted by tips

Hi Mike,

I have just had a reply on another forum that they do run hot and that there isn't a problem with it (I thought there was).

Thanks

I would ignore that if I were you.

The wires that trigger the relay can pretty much be any old crap, although I'd personally reccomend 24/0.2 cable for that (that is 24 strands, each strand having a 0.2mm thickness).

The power from the battery to the relay for the actual fan wants to be considerably thicker, I'd say at least 32/0.2. The same size also applies from the relay to the fan itself.

Ditch that crappy in line fuse holder you have as well, get something that is actually man enough for the job because you should not feel it getting hot.

**coin-op** · 27th September 2008

Originally Posted by Pegasus

Ditch that crappy in line fuse holder you have as well, get something that is actually man enough for the job because you should not feel it getting hot.

Spot on Pegasus. Quite often these shitty little fuse holders present a load and act like little heaters.