Fan Resistance

[kroberts]

I have a generic question about DC motor resistance. I'm trying to troubleshoot a problem and need some help. My fan quit working. None of the pertinent parts are BMW. I have an old-ish Flex-a-lite fan, controlled by an external relay, in a S52 swapped E30.

I have 'triple-checked" my wiring, all is correct. I know my ground is good. I put an ohm meter across the leads to the fan, I'm getting 0.8 ohms. That seems a little low to me. Would that cause a relay to fail to operate? I suck at electrical troubleshooting and theory.

Any input from the Literati would be appreciated.

kr

[Jean]

Sounds about right, 0.8 ohms at 12 volts is about 15 amps of draw. Did you disconnect the fan wires from the resistor when you measured ?

[AndrewBird]

Simple test. Hook the fan up directly to power and see if it comes on. If it does, it's more then likely the relay. If it doesn't, it's the fan.

[kroberts]

I cant figure out why the hell this thing quit working. It works if I hard wire it to a battery. How much voltage does it take to operate a standard automotive relay? I haven't driven the car in about 6 weeks and the battery is down a little. I'm going to charge it up.

[jlevie]

The usual automotive relay will pull in at a system voltage lower than that required to start the car. If the relay won't close when you jumper power to the coil, you've got at a bad relay or bad ground.

Is there a thermoswitch in the relay circuit? That would be another point of possible failure.

[kroberts]

Well it must have been a bad connection. I removed everything and re-terminated all my connections. I installed the parts and now it's fine.

Annoying.

Thanks for the replies,

kr