James wrote:
>
> I got my 77B with only one electric fan and when it failed I replaced it
> with a 12" fan from Imperial. Instead of using the sensor that Imperial
> supplied I decided to use the temp sensor that powered the fans in the car.
> After testing the wires, I found that the temp switch was positive
> (confirmed with the wiring diagram as well). I snipped the black wire from
> the switch to the OEM fan and connected this to the new fan, and then ran a
> new ground wire. This ran fine for a week but then the fan died. After a
> few minutes of poking around I found this:
>
> 6V current was running through wires, but when I connected the fan it
> dropped to 0 with no fan action.
>
> The wire coming from the temp switch was now ground???
>
> Running a line directly from the 35 amp fuse ran the fan fine, using the
> same ground wire.
>
> What happened???
James -
Just a theory, but I suspect that your temp switch has failed. It
probably has developed a high internal resistance - which is why you are
measuring 6V instead of 12V with the fan disconnected and 0V when the
fan is there. My original switch was bad when I first started the car
after a rebuild. Ordered a new switch - it lasted about 3 weeks (200
miles) and failed also. The fans were only drawing about 10 amps
total. Don't know what the switch is rated, but I opened the failed
one; the contacts are rather light duty looking. I added a 30 amp
relay, with the temp switch controlling the relay and the relay
supplying the voltage to the dual fans. So far, working well.
Wayne Kube
'79B
Plano, TX
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