is it ok to put a standard 5 prong relay on a ground wire instead of the power wire? it would just make my wiring alot cleaner.

getting pissed at my e-fan running for 10-15 mins after car shuts down. gona put an ign relay on to work with the temp switch so it dies with the car.

so I wana put it on the fan ground wire instead of the power.

ok?

 

People do it for their antennas. I dont see why you cant for your fan.

 

I'm thinking it should work..

cause when 86 gets it's ign source, it gets grounded to 85.

and that just compleats the circit between 30 and 87 right? shoudln't matter which way it flows through there.

I think I got those numbers right

 

Scott, an extra relay isn't required. If you wire it as per my wiring diagram in this thread, it'll only run when the ignition's on.

 

you're not understanding my question
your pic




what I want to know is. instead of cutting the power wire to the fan and putting the relay in. I wana put it on the fan ground wire.

so 87 would ground. and 30 would go to the ground on the fan.

it would just make the wiring alot cleaner. as the relay and wiring would be hidden if I put it on the ground. where as the power wire is in open veiw going from the power source to fan.

 

the question doesn't need to have anything to do with fans... it's just a question if standard 12v relays can go on ground wires instead of power wires

I think it's the same thing.

 

what happens if the diode fails

 

yes, it doesnt matter where it is in the circuit... the electrons actualy flow from neg to pos... but thats another story all together...

just put it wherever you want in the circuit, it will be fine

 

Ha ha, you're right, I misunderstood.

It makes no difference if you switch the ground wire instead of the power wire. The reason I've always wired mine up like that is that you can usually use the mounting bolt of the device you're switching (fan, lights, etc) as a ground point, to keep wires short.

The same goes for the control side of the relay. You could put the temp switch on the other side of the coil (pin 86) and it would work the same, but I usually just run a short length of wire from that pin, put a ring terminal on the end and put it under the relay's mounting screw. Easy.

But the fact the you fan runs after shutdown means the coil (86 & 87) is still receiving battery power. It should come off an ignition source if you want the fan to shut off with the engine.

 

Yup, just swap the + and negs on the relay and make a ground switched relay. It works with careful attention to what you are doing. You can use a 4prong relay too-- its a little bitless confusing. Also, there are a couple circuits on our cars that use a ground relay anyway. I believe the fog lights are one.

 

Warning!
You may have other problems.
Unless you have a variable T-stat set unusually low, the fan should not take more than 30 seconds to cool enough to shut off by itself.
I have the low end of E-fans (from a Tarus) and a fixed stat.
The most it runs is about 20 seconds after the ignition is off.