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Hi folks, I spent the day bypassing a defective Fan Control Module (FCM), so I wired the power directly to the fan motor.

The garage wanted $350 CAD to put a new fan in but couldn't justify this expense on a car with such high mileage and age (not to mention rust). The mechanic said I could drive it without a fan, unless I get stuck in traffic, it will overheat. Basically I want to keep the car going for another year. I also need my A/C, and right now it works, unless the temperature goes up as I said. So, I decided to bypass this FCM ( I cut the wires and removed it), and applied power from the fan connector (female) directly to the fan motor, and as expected it worked beautifully.

Now I am at the wiring stage and need help with threading this large gauge wire pair through the firewall to a heavy duty toggle switch to the left near the dash illumination thumbwheel control (2 spare slots there). I am going to break the circuit at the fused red (+12V in the female fan connector), and place the switch in series to turn it on and off manually (black/gnd is not switched). This protects the motor with the existing 40 A fuse. Is there a spare spot I could use to pass the wires through without too much difficulty? A Youtube video of a similar job mentions there is a 'white plastic cover' but doesn't indicate where. I don't want to drill willy-nilly and cause damage.

Also what do you good people recommend for operating the fan switch, and can I overdo it and burn out the fan motor? I am going to test drive this when I am done and operate it when stopped in traffic or not moving fast and /or when the A/C is blowing out hot air. If I had more time, and patience (sadly both diminishing at 56 !) I would build a circuit to turn it on automatically with the third "control" wire (purple) - educated guess here , unverified. Anybody know what voltage this wire should be when the pulse comes in from the PCM (to cool cool rad) ?

Btw, I found the red wire to the input of the FCM disconnected as I was removing it - I may have done this when I was fudging with it, they are coroded and brittle - wouldn't that be something if it was just a disconnected wire? (doubt it though).

Any other tips or help greatly appreciated.

Oh and I found some FCM's cheap'ish, but read these fail often.

p.s. I am using large gauge C-band motor cable and should be okay, will check switch current rating. I hope to have this done by tomorrow noon and test it, so will report back.

p.s.s. Any quick and dirty way to run it inside w/o drilling through firewall, short of running it through the window ;) ?

Cheers
 

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Discussion Starter #2
Quick update for anybody who still cares ;-)

Ran the cable temporarily through the passenger window, and took it for a drive toinight and despite a heat wave here the A/C worked fine (not great, but Mazda A/C suck anyway as we all know).Ran the fan all the time as the A/C was on constantly, which is at it should correct? I am still nervous about overtaxing the fan but i have no choice, it's flippin hot and humid here and this will have to do until I can get a new car. I lucked out with a heavy duty "stomp box" DPDT toggle switch I had in my junkbox,and although the wire gauge could have been larger, it just gets warm to the touch, not hot. (not all Direct burial cable are alike, I have another that uses larger gauge , forget the number, 10 or 12 I believe that matches the fan motor's gauge: this bugger can draw some hefty current, hence the 40 A fuse!

It's a pain to have to keep an eye on the temperature gauge and remember to flip this on and off: next, version 2 will have a pilot light to remind me. I know the fa control module uses PWM to vary the fan speed. Well, see over 100 people read this but still not reply, oh well, I know it's an old p.o.s. but still glad to keep it going a little while longer and save some green too. Tomorrow, it's poking and prodding to run this through the firewall and mounted properly. Will be glad when it's over.
 

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use a smaller switch to drive a relay, closer to fan controller
if you want to automate it use a temperature switch to turn relay on
 
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