Quick question: Adjustable Thermostat Probe Location

tngbody

Greasemonkey
Sep 17, 2019
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I have a dual fan setup installed and wired up, however the instructions seem to show the probe laying on the radiator fins. I have three scenarios and I'm not sure which is best. So I need someone to tell me the best option for installing the probe. I have attached 3 pics showing each option.

Option 1: Placing probe flat against fins.
Option 2: Use the clamp that holds probe close to fins but not touching.
Option 3: Push probe through the fins perpendicular.
 

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78Delta88

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It needs to go laterally or perpendicular against the fins... I.E.: metal to metal contact.

On the scenario where you show the prob laying on top of radiator. There are actually some spring clips that fit in there and they will hold the full length of the probe snug against the top of the radiator. I am just not aware of who sells them.
 
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78Delta88

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With clamp as you show, it's being insulated by the plastic cover of the clamp plus you have too much air space. Air is a great heat insulator.

Stabbing it through the fins you can damage the fins but more importantly the thermo couple will not work properly.

I like this setup better...

Screenshot_20230805-163141.png

The switch is mounted directly into the water jacket. It mounts into intake manifold or thermostat housing and is the outlet flow from the heads. Most switches turn fans on when temp hits 185*F and shuts off fans at 165*F

Splitting hairs maybe a bit, but you want the fans to come on when there is hot coolant needing to be cooled regardless of radiator temperature. Realistically the radiator is hot, but by measuring the actual coolant temperature to turn the fans on is much more robust and less failure prone.

The above is just an example of using the temperature switch type system. Several sources make this type of system.
 
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Oct 14, 2008
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I clamped mine against the upper rad hose. It isn't very accurate according to the Davies Craig controller but at least I didn't damage fins with the probe.
 
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78Delta88

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Thanks for the input. Been a while since I used that style. It was in a 64 F100 and had brass tanks.
 
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Ugly1

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Oct 26, 2021
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It should go on the hottest end of the radiator about 1/4 way down as most fan controls are just before the thermostat. It needs to be as close to or up against the tubes as possible for the radiant heat. 78Delta88 shows the best way and have it right in the cooling system. Set it up like a Camaro’s would probably be spot on.
 
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tngbody

Greasemonkey
Sep 17, 2019
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This is what I ended up doing. Issues?

PXL_20230808_230014345.jpg
 

78Delta88

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Looks like it should work. Time will tell.
Keep check on the zip tie if/when it breaks ... The housing will come loose.
 
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Rt Jam

G-Body Guru
Mar 30, 2020
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With clamp as you show, it's being insulated by the plastic cover of the clamp plus you have too much air space. Air is a great heat insulator.

Stabbing it through the fins you can damage the fins but more importantly the thermo couple will not work properly.

I like this setup better...

View attachment 225830

The switch is mounted directly into the water jacket. It mounts into intake manifold or thermostat housing and is the outlet flow from the heads. Most switches turn fans on when temp hits 185*F and shuts off fans at 165*F

Splitting hairs maybe a bit, but you want the fans to come on when there is hot coolant needing to be cooled regardless of radiator temperature. Realistically the radiator is hot, but by measuring the actual coolant temperature to turn the fans on is much more robust and less failure prone.

The above is just an example of using the temperature switch type system. Several sources make this type of system.

It is not splitting hairs. Into the coolant is the only proper way to read coolant temperature.

A dry probe on the radiator, whether it's in the fins or on the fins on contacting the tank has a major flaw with this set up. As air flow through the grille will change the reading to lower than what the coolant may actually be at.

I do support adjustable so you can adjust it to just above your thermostat temperature. If you have a non adjustable set up at say 185. If you have a 190 thermostat. You will be in a situation where the fan turns on before the thermostat opens. Blowing air across a radiator that is not flowing is just a waste of energy.
 
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78Delta88

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One of the reasons I like the switch to be in the coolant is for the reasons you state. Yet, I try to help the OP with his question related to the equipment has. The way it is setup currently it is above the fan so other than ambient flow, the air flow is negligible for the equipment he has with his current setup.

Who knows, maybe it won't work. Maybe in a month or two he can or will change it to a different system.

Likewise, as you state and are correct, the fan might turn on with no flow. Yet, when the thermostat does open, it will be flowing and the radiator will be full of hot coolant and the fans will be on.
 
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