Electric fan wiring...

[vanzuuk1]

My electric fans dont seem to turn on consistently,sometimes not at all.


If I ground the sending unit (in the head) to the frame with they key in the off position the fans kick on, so I know the fans get power.


If I turn the key to the on pos with the sender still grounded the fans shut off...is this a wiring issue or is the sender bad???




Thanks

[MonzaRacer]

What kind of setup do you actually have? If you have simple 5 pin relay and are using the sender to ground out the relay and powering it with key on recheck every connection. Most 30 amp relays have 5 terminals 85,86, 30,87,87a. Now 85,86 are pull in terminals(one to ground one to key power), 30 should be battery power (fused) and 87 or 87a will be what you want to power.
Big tip, look at relay diagram on side/top, if it shows diode between 85,86 one way blocks voltage spikes as it opens and closes, diode sign looks like this ->I and arrows shows current blocking direction, like if the bar side is a computer.
If is has zigzag line it can be hooked either way as its resistor damped.
Honestly on most of my electric fan cars I simply tied both power wires directly to battery with a fuse. I never worried about using key to turn it on, and I never ran a battery down or had starting issues. Fans usually ran a minute or two max, then stopped.

[TnBlkC230WZ]

If you have a 5 pin relay, SPDT you may have the fan power wire connected to the 87a terminal. It needs to go to the 87 terminal.