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Secondary fan running AGAIN!

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Old 07-23-2015, 07:46 AM
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Car: 92 Formula WS6, T-top
Engine: 5.7L T.P.I.
Transmission: 700r4
Axle/Gears: Limited slip, 3.23 10 bolt
Secondary fan running AGAIN!

I had this issue when I first bought this car, and fixed it last summer. Back then the secondary fan ran constantly, even at cold startup. The pigtail connector was shorted out, so I replaced that, and it stopped running all the time. But here over the past couple weeks I noticed that it's running again, but only when the motor warms up. If you go out when it's cold the fan does not run. So if it's heat related, it's electrical. I'm thinking bad fan switch, but what do you think? I mean, there's the wire, the relay, and the switch--that's about all there is on the secondary fan because it's not ECM controlled. Has to be one of them doesn't it?
Old 07-23-2015, 09:32 AM
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Car: 1989-92 FORMULA350 305 92 Hawkclone
Engine: 4++,350 & 305 CIs
Transmission: 700R4 4800 vig 18th700R4 t56 ZF6 T5
Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Secondary fan running AGAIN!

Its not supposed to run unless the engine is 239 degs or the A/C is on.
Old 07-23-2015, 09:57 AM
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Car: 92 Formula WS6, T-top
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Transmission: 700r4
Axle/Gears: Limited slip, 3.23 10 bolt
Re: Secondary fan running AGAIN!

Originally Posted by TTOP350
Its not supposed to run unless the engine is 239 degs or the A/C is on.
LOL....yeah, I know that, but my question is WHY is it running when the temp is only 160-200ish? I never use the AC in this car, it doesn't even work. The secondary fan does not run when the car has been sitting for hours and you turn the key on or start it, but WILL run if you turn the key to the "on" position before the engine has totally cooled down. Dont even have to start the motor, so it's temperature related--which probably means electrical issue. Like if you just got home and forgot to roll the windows up, and turn the key on to do it? The fan can be heard. But this morning I checked on it, and it did not come on after sitting all night. So, is there something besides the relay, wire or switch? And could a worn out switch cause it to come on too soon and stay on longer? This is different than what I had last summer when it ran constantly in all conditions.

Last edited by TheExaminer; 07-23-2015 at 10:01 AM.
Old 07-23-2015, 10:02 AM
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Car: 1989-92 FORMULA350 305 92 Hawkclone
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Axle/Gears: 3.70 9"ford alum chunk,dana44,9bolt
Re: Secondary fan running AGAIN!

COuld be a stuck/sticking switch or relay. These cars are old now lol
Old 07-23-2015, 10:23 AM
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Re: Secondary fan running AGAIN!

I know you probably heard this, but did you check out the resistance of the switch? It might be bad as mentioned by TTop
Old 07-23-2015, 10:26 AM
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Re: Secondary fan running AGAIN!

Yeah, switch was my first suspect, but I didnt have that resistance chart. That'll be helpful, thx guys!
Old 07-24-2015, 05:42 PM
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Re: Secondary fan running AGAIN!

The fan switch is only on or off. It will only be open or closed to ground if you meter it. Temp sender and sensor will vary ohm, though.

Testing it in heated water on a cooktop with a thermometer is how you can verify what temp the switch closes at or, just replace it. They are fairly cheap.
Old 07-24-2015, 08:25 PM
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Car: 92 Formula WS6, T-top
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Transmission: 700r4
Axle/Gears: Limited slip, 3.23 10 bolt
Re: Secondary fan running AGAIN!

Originally Posted by deadbird
The fan switch is only on or off. It will only be open or closed to ground if you meter it. Temp sender and sensor will vary ohm, though.

Testing it in heated water on a cooktop with a thermometer is how you can verify what temp the switch closes at or, just replace it. They are fairly cheap.
I may replace it, but if it's on or off, what do you think is causing the fan to kick on earlier than it should? I guess what I'm asking is, could an old or worn out switch be closing sooner than it should be? Since this is the secondary fan, the cts doesn't come into play does it? My temp gauge runs in the 160-190 or so range, never higher. Hopefully that is fairly accurate.
Old 07-24-2015, 08:59 PM
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Re: Secondary fan running AGAIN!

I can't speak of how the switch closes (as I don't know) but, I can only assume, like a thermostat, eventually over the years and cycling of temps, it's bound lose its tolerance and eventually to fail (or operate outside of its parameters). Similar to the ohm rating of a sender/sensor failing and providing a false reading.
Old 07-24-2015, 09:43 PM
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Car: 92 Formula WS6, T-top
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Transmission: 700r4
Axle/Gears: Limited slip, 3.23 10 bolt
Re: Secondary fan running AGAIN!

I hope that's it. Switches are cheap and easy to replace, but I HATE chasing down wiring and electrical issues. Last year when it was running all the time, the connector literally crumbled in my hand when I pulled it off, and had bare wiring on it. After I replaced that, it quit running all the time.
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