radiator fan

[FordPrefect]

Alright guys.

So I had a mechanic look at my car, and it turned out that the battery was low. I had it charged, and it was enough to spin the engine, and the voltage measured ok, but I guess it just needed a more powerful charge than my ancient trickle charger was capable of...

Anyway, now the radiator fan doesn't turn on.

I powered it directly, and it spins up really well, but when I bypassed the switch on the radiator, I can hear clicking in one of the relays, but the fan does turn on.

I'm not 100% sure I've tested the switch properly, or how I'd test the relay exactly. Should I maybe bypass all that rigmarole and just wire a switch to the dash somewhere maybe?

I let the car idle for a while at one point to test the fan, and the temp gauge in the dash was pegged, so I shut her off for a few hours. When I went back out, I noticed the car began to die after idling for a while. Is that possibly related to overheating?

[RRoller123]

The thermal switch controlling the radiator fan is in the bottom corner of the radiator, driver's side, and all you need to do to test it is to short the terminals, (carefully, the circuit draws significant power) as it provides a path to ground when it hits temp. If the fan runs when the switch is shorted, then the wiring to ground is ok. If not, follow the grounds out od the switch and over to the ground pod on the inner fender wall, driver's side. They get really crappy over time. You can also pull the switch itself and put it into a pan on the stove with a thermometer and see if it is closing somewhere around 195 deg F. A plumber's thermometer from Home Depot or Lowes works well to check the temp. Resistance goes basically to zero when the switch closes at temp. Hope this helps.

[FordPrefect]

I cleaned that particular ground not too long ago, actually. I pulled the wires off the switch and touched them together to test them (heard a click, but no fan), that should have the same effect as shorting them together on the switch, shouldn't it?

Thanks!

[RRoller123]

How did you power it directly when you tested the fan itself? From the car battery?

[FordPrefect]

How did you power it directly when you tested the fan itself? From the car battery?

Yes.

[RRoller123]

So it could be low voltage getting to the fan, since direct power from the battery runs it fine. Th eblue wire has a couple of connections that should be checked. Here is the schematic from my 1980, probably best to trace the power supply to the fan from the fuse and make sure that it is getting to the fan with enough voltage. It is the light blue wire from fuse 10

[FordPrefect]

I traced the problem to a corroded connector between the fusebox and the relay itself, thanks for the help guys!

[RRoller123]

That's great! What year is the car? I didn't think the fans ran on a relay?

[FordPrefect]

That's great! What year is the car? I didn't think the fans ran on a relay?

It's a 76, I think.