High Speed Fan Relay Burnt

[blkgt09]

The high speed fan relay burnt twice this week. All the information I could find online suggested adding universal relays..

So i installed the relay last night.. I also added 2 indicator lights. The blue light was terminated on the normally closed circuit so i could see when the relay was on or off ( if the relay is off the light would be on, if the relay was on the light would be off)... The green light just showed that I had power going to the fan, when the relay was on.

Well upon finishing I took the car for a ride. The fans came on and off throughout the drive.

Now, here is where im having a hard time understanding whats going on.. I was under the impression that computer sends a ground signal to the relay and that a constant 12v's is what turned on the relay..If thats true my blue light should of went off, but it never .

I checked voltage. I found that the normally closed and normally open circuit had power on them.. As if the relay was not fully seated in either direction. I checked the coil and had 12v's on both sides..

That is where im hung up, why does it seem the computer is sending 12v, what kind of signal does the computer send?

Im considering just puting a switch in it and not relying on the computer.. Should i remove the low speed relay and just run high ?

 

[83-88T-Bird Guy]

edit: (I just re-read your post....you are having trouble on the high speed side, but cutting and re-routing the hs fan wire thru an external relay still works on the same principal)


Not sure if any of this info is useful to you, but here goes.

Last week on my 2005 GT, I installed an aftermarket 30 amp relay to the low speed side of the fan.
The reason is because I had heard horror stories of burnt up factory location relays so I wanted to try and prevent it on my car by using an external relay.
Plus, I wanted total manual control over the fan for cool downs between runs.

( my high speed still functions as normal by the ECU, but I hope I never need high speed)

The high amperage wire that comes from the factory low spd. relay in the fuse block is green with a yellow stripe, and was cut and dead ended.

I then ran a fat wire from that factory (green/yellow stripe) on the fan to my new relay which in turn is hardwired into the fuse block.

With a switch on the dash for my new relay, I have total control over the low speed and the high speed side functions as normal.

With a car that has a/c or is driven on the street, there is a way to build a fail safe to kick the fan on low speed when the computer says so, while still having manual control over the low speed side.
I haven't finished the layout yet, but it involves a diode.