finkbuilt

fan switch in radiator plug topic again

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Get the 91* thermo switch part #61311364272

I have that setup and its flawless. Beaner7102

Really? This works for people?

I tried putting the 91deg switch in the radiator drain (E21 rad), and the fan never comes on. I let it get up right to the red before shutting it off.

I checked my wiring, and all is good there. I went according to the Zenon Diagram. I bridged the switch contacts and the fan comes comes right on. Override switch works as expected too.

So then I switched to the "special" 85deg switch that Bavarian Autosport sells specifically for mounting in the radiator (they acknowledge that the 91 does not work for this application) , and it does the same thing - fan never comes on with needle nearing red.

I'm sort of getting tired of overheating my engine to test fan switches, I've cracked too many heads in my 02 career.

I guess I'll try putting it into an E30 water neck next.

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Guest Anonymous

Carl at La Jolla Independent straightened me out on this. The drain plug location is the coldest location in your whole cooling system, which makes it not he best place for your switch.

Put the switch in the outflow fitting to the top radiator hose. That way you are using the hotest coolant which has just run through the engine to turn on the fan.

Have fun

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Yep, makes sense. Also, the switch can work poorly if one uses teflon tape, as the electrical connection and temp readings can be compromised.

While we're on the topic of coolant temps that vary based on location in the radiator, given the opportunity one should mount an electric fan as high as possible on the radiator core.

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Yep, makes sense. Also, the switch can work poorly if one uses teflon tape, as the electrical connection and temp readings can be compromised.

This is because the body of the sensor is the ground.

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Yep, makes sense. Also, the switch can work poorly if one uses teflon tape, as the electrical connection and temp readings can be compromised.

This is because the body of the sensor is the ground.

This is true in the case of temp sensors, which need to be grounded, but not temp switches, which are isolated from the switch body. Hell, the radiator tank is plastic.

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Steve, you know you can drive the fan relay from the megasquirt if you're not using the fidle (terminal 6 on the relay board) for something else. See the spare port settings on the msq I sent you. This way you can set it to come on at whatever temp you specify.

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Yep, makes sense. Also, the switch can work poorly if one uses teflon tape, as the electrical connection and temp readings can be compromised.

This is because the body of the sensor is the ground.

This is true in the case of temp sensors, which need to be grounded, but not temp switches, which are isolated from the switch body. Hell, the radiator tank is plastic.

Thanks for clarifying.

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Yeah, that switch location is for the 'OH SHIT' sensor that only

comes on IF the radiator is all hot.

t

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The switch I am using is grounded through the body of the switch, that is why I had to run a ground from the metal tube thing.

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Steve, you know you can drive the fan relay from the megasquirt if you're not using the fidle (terminal 6 on the relay board) for something else. See the spare port settings on the msq I sent you. This way you can set it to come on at whatever temp you specify.

Yeah, I'd like to do it that way, but this is actually pertaining to my 4 door, which is not 'squirted just yet. But soon!

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Is the lower hose getting Hot? perhaps your T-stat is not working properly. i have the 85c switch in the bottom of the rad and it switches fine when engine is in the 185-190 range.

It seems that if the switch was in the top hose area, the fan would come on early and OFTEN.

Your t-stat should be opening or closing first, at what ever temp it is, then when the Rad gets hot the fan should switch on. by the way what is the T-stat rated at? Have you tested that?

Have Fun

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