78 280Z Electrical Fan (Not how to install)

[kutukutu1]

Hey all, i made the install and the fan works fine, but i have the most bizarre issue which i cant figure out.

The install kit comes with a wire so you can put a manual switch to turn on the fan on top of the thermostat switch turning on the fan.

So the fan turns on with the manual switch, but here is the strange part. If i dont manually switch it on and let the thermostat switch do its thing, reach temperature, it does not turn on the fan unless i give it a jump start with the manual switch. If the temp switch is at its working temp, i have to toggle the manual switch to get the fan going, then it stays on. 

I used a voltmeter and checked voltage going into the temp switch, i get 12V, if i jump the switch with a wire, suddenly the voltage drops to 7V. When i jump the temp switch there is nothing in the circuit but wires and the fan so i am at a loss as to why thats happening and why when i give it a jump start with the manual switch, it does work.

Any ideas?

[SteveJ]

Not without a wiring diagram.

[kutukutu1]

Sorry about that. I wired it per the diagram it came with.

https://derale.com/product-footer/product-instructions-footer?download=251:16739&start=240

 

[SteveJ]

That works. See the questions in the image.

[kutukutu1]

Just now, SteveJ said:

That works. See the questions in the image.

If i read that point to ground, i get 12V.

[SteveJ]

Please answer both questions. 

[kutukutu1]

I tapped into the relay line for the AC. I dont have an AC system and the connector had been damaged so i used that line since it was a switched 12V.

thanks

[SteveJ]

How much resistance is there in the thermostat switch? Is the AC relay completely unplugged?

[kutukutu1]

It is not the thermostat switch, to see if it was the switch, i unplugged the connection to the switch and just jumped the connection with a wire. When i do that, the same thing happens and it drops to 7V. The AC relay is not unplugged, you think that could be a possible culprit? Ill unplug it and test that out as soon as i get my injectors back on and the engine started again. Ill post back as soon as i try it. thanks

[kutukutu1]

Alright, solution!!!!

I had tapped for 12v switched at the yellow line that goes to the ac relay. This made it run thru the inductor of the relay causing the voltage to drop and making it too low to start the fan, but enough to latch the relay switch if a jump started. I switched the wires and wired the 12v switched to the blue and white line going into the relay. There is a blue and white coming out of the relay so make sure you don't use that one. Everything worked after that. 

Thanks you all for the help

[SteveJ]

This may help you with your understanding of relays: https://fiddlingwithzcars.wordpress.com/2012/12/22/relays-simplified/