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Old 09-20-2020, 08:34 PM   #1
OUbesto
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what degree thermostat do I need

I just installed twin electric fans and installed the relay kit they supplied along with a "185 on/165 off" Thermal Switch....so what temperature thermostat should I use for my radiator? I read on the forum that the thermal switch "off point (165) should be above the t-stat. If true, that means I would have to install something in the 160 degree, right? That seems way too low????? Any thoughts???
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Old 09-20-2020, 09:00 PM   #2
truckster
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Re: what degree thermostat do I need

A 160 degree thermostat would not be ideal for efficiency. I would say a minimum of 180. You might need to change your sending unit if the fans run constantly.
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Old 09-21-2020, 01:07 PM   #3
tdangle
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Re: what degree thermostat do I need

I also would recommend at 180. The thermostat temp sets the minimum operating temperature of the engine, once open the engine will run at whatever temp is normal for that engine and outside weather temp.
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Old 03-29-2021, 05:06 PM   #4
68 P.O.S.
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Re: what degree thermostat do I need

The thermostat and thermal switch should match. 180 or 185 would probably be ideal.
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Old 03-29-2021, 09:10 PM   #5
RustyPile
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Re: what degree thermostat do I need

I have this controller on my fans.. It's adjustable..

https://www.summitracing.com/parts/der-16759
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Old 03-29-2021, 09:30 PM   #6
72c20customcamper
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Re: what degree thermostat do I need

185 on and 165 off in my opinion is way to low . I have 195on and 180 off on my 496 Chevelle fans run a short time to get it down ,the thermostat I used is a 160 with two small bypass holes I drilled into it . 165 is to cool for the motor to run efficiently and I think your fans will run alot. Did you also change out the alternator ? I put a high amp on it with a heavy gauge wire from the alternator to the battery .

If you run a 180 thermostat it will start to close when the water temp gets below 180 that's its job to keep the motor at temp . So the fans will be fighting the thermostat
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Old 03-29-2021, 09:47 PM   #7
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Re: what degree thermostat do I need

I'm assuming you still have a carbureted 402 in your truck. For that I would use a 180 thermostat. The thermostat should match what your engine needs, regardless of what your thermal switch is doing.

The fan will just be running some when the thermostat is closed. So, it won't hurt anything other than being noisy.
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Old 03-29-2021, 10:44 PM   #8
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Re: what degree thermostat do I need

On my LS project swaps I use a 180 degree thermostat. Fan control is set at 215 on and 195 off. Gives me some room over the 180 degree thermostat.
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