1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

stock clutch fan not kicking on

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Old Apr 6, 2018 | 10:36 PM
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stock clutch fan not kicking on

hello everyone,
My SE clutch fan does't kick on no matter how hot it gets. Looking at the FSM, it appears that the sensor on the bottom of radiator (water temp) is the one that signals the fan to kick on? The top sensor is just for level, and the one in the water pump housing is for the ECU and emissions. Is there another sensor that I didn't see that my also work the clutch? If it is the sensor on the bottom of radiator, is an aftermarket one from like Rock Auto ok, or should these sensors be bought from the dealer? The fan clutch itself seems to be ok, as it free spins when warm, and has resistance when cold.

Thanks!
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Old Apr 7, 2018 | 12:51 AM
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the stock cooling fan clutch is not electrically controlled.
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Old Apr 7, 2018 | 09:17 AM
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It's filled with an oil/liquid that heats up. One way to test if it's working is to spin it by hand when cold. it spins easy, it not good.
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Old Apr 7, 2018 | 10:21 AM
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From: https://www2.mazda.com/en/100th/
i did some testing and the fan comes on at about 91c or when the gauge is about 2/3rds of the way up. since this is pretty hot, it actually won't run that much. the freewheeling fan must move enough air to keep things mostly fine

another thing to check is if the radiator is clogged, if the radiator is clogged in front of the fan, it won't get hot enough to get the fan running
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Old Apr 7, 2018 | 07:59 PM
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From: Summit Hill, PA
Originally Posted by rxtasy3
the stock cooling fan clutch is not electrically controlled.
Thanks! I was assuming that the temp sensor on the rad controlled the clutch somehow, but now that you mention it, there isn't any electrical harness going to the clutch, duh.....I feel like an idiot now......lol! I'll have to remember that my clutch fan doesn't operate like the e-fans on all my other cars, lol!
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Old Apr 7, 2018 | 08:04 PM
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From: Summit Hill, PA
Originally Posted by KansasCityREPU
It's filled with an oil/liquid that heats up. One way to test if it's working is to spin it by hand when cold. it spins easy, it not good.
Thanks KCRepu!

I think in my original post I worded it backwards for the testing of the clutch, lol! But yes, it is working properly as far as that is concerned.
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Old Apr 7, 2018 | 08:12 PM
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From: Summit Hill, PA
Originally Posted by j9fd3s
i did some testing and the fan comes on at about 91c or when the gauge is about 2/3rds of the way up. since this is pretty hot, it actually won't run that much. the freewheeling fan must move enough air to keep things mostly fine

another thing to check is if the radiator is clogged, if the radiator is clogged in front of the fan, it won't get hot enough to get the fan running
Thanks j9fd3s! I didn't realize that the gauge would rise that much for the fan to kick on. It's probably not getting hot enough then, as it is still winter weather here in pa. I guess I'll now for sure when the summer comes. I plan on servicing the A/C too, so that will also be help test the clutch.

The other question I have has to do with where the gauge needle is sitting when it reaches full operating temp while driving. Mine only moves 1/4 of the way over. I have a 180 degree thermo in it. Can anyone else confirm this? Like I said, it's about 1/4 of the way when at full temp and the car is moving. Sitting/idling after when fully warm, the gauge gradually moves over to the middle or so.
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Old Apr 7, 2018 | 10:50 PM
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From: Coastal
My stock temp gauge stays about 25%, too. But it has stayed consistent like that for years without problem. Needle goes up abit on hot days and I'd be concerned if the water temp reaches 60%. I would shut off the car at 60%. I have a black magic electric fan that kicks in before temps get that high. I have a redundant system of newer digital gauges to monitor water temp and oil temp more closely, and they are not 1:1 to the stock water temp gauge, and as long as they all read consistent without much volitility, all is good.
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Old Apr 8, 2018 | 09:39 AM
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Temp gauge at 1/4 is just right, especially for winter. Even in the heat down here it only goes to 1/3.
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Old Apr 8, 2018 | 10:10 PM
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From: Summit Hill, PA
Thanks guys!!!
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