Ok, so the idiot who had my Z28 before me apparently wasnt interested in fixing things right. Apparently, the radiator fan switch went out, and instead of fixing it, he chopped up the wiring and ran the power wire for the fan motor (surprisingly through an in-line fuse) straight into the ignition, so the fan is on whenever the key is on.

I'm going to fix this, get a new fan switch, etc. It makes sense to me, that if I run the power wire from the fan motor to the fan switch, this will work as it should ... right? Anyone have further input on this? Am I missing something? Cant be this easy ...

 

What fan switch are you talking about? There are no fan switches on a stock car. The Computer turns on one of them at a predetermined temp. The second comes on either with the AC or from another temp sensor.

To get your fans to come on with the ignition switch doesn’t require a hack job, just cut 1 wire at the fan relay and ground it

 

Isnt there a fan switch in the pass side head that determines when the fan kicks on? And if the ECM determines when, why doesnt it kick the fan on at all?

 

There is on my lg4...

 

That's the fan switch.

 

OK, when I think of a switch I think of the kind people install the dash. If you call the temp sensor a switch then technically the Relay is also a switch.

Oh by the way, I've been running my IROC with the fans coming on with the ignition for 2 years and my car hasn't overheated since I did it. It overheated plenty before though. You can me a hack for cutting 1 wire if you want but my car is plenty happy this way.

 

No, a switch is not the same as a sensor. A sensor implies it has a range. A switch exists in only 2 positions; on and off. The fan switch is simple. When it gets hot enough, it grounds the contact on it. Simple as that.


Oh and it's also bad to run the fan all the time. There is such a thing as running too cold..

 

My car runs at 210* all the time because it has a thermostadt. What bad thing happens from running too cool? I know what bar things happen from running too hot. Maybe if I was from Minnesota I might have a problem but in So. Cal. it's all good.

Heat is the enemy.

 

The thermostat will keep it from running too cold.

 

Ok, so I still havent gotten an answer to my question. Why doesnt the fan come on when it should if it isnt run straight into the ignition? And if I do leave it running to the ignition, I noticed the wire gets quite warm .... do I just need a bigger gauge wire?

EDIT: I guess my question is, if I am going to leave it wired to the ignition, what is the proper way to do it so nothing is damaged?

 

You need to use a Relay, the secondary of the relay should heavier gauge wire while the primary could use smaller wire.
There is a factory Relay for this but if it's hacked up like you say you can get a new one at the Parts store. Anyway here's a real simple schematic that will work.

Attachment didn't work I will try in next reply

 

Try this

 

Looks simple enough, thanks Ringo.

 

except the fuse should be before the fan, not after.


Apeiron: Right. My bad.

 

Why does it matter which side the fuse is on? Current is the same on both sides of the Fan.

 

A fuse in that location isn't going to protect against a short to ground in the fan. The fuse should be as physically close to the positive power supply as possible.

The fuse in the relay circuit is probably unnecessary, since the convenient sources of switched +12v power are already fused.

 

A short to ground on the negative side of the fan won't blow the fuse even if the fuse was on the positive side. The fuse will blow if the positive side shorts to ground even if it's on the negative side.

 

A short to ground on the negative side of the fan won't blow the fuse, because it isn't a short.

Your fuse on the negative side will not blow if the positive side shorts to ground, because there will be no current flowing through the fuse.

 

I suppose but a short before the fuse on the positive still won't blow the fan fuse but it might blow a fusable link or a main fuse depending on where you pick up the 12V in the first place.

 

The idea is to avoid blowing fusable links. That's right though, a short before the fuse won't blow it, that's why the fuse is placed as close to the +12v source as possible, so there's as little unfused span of wire as possible for a short to develop in.