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Looking for an auto temp switch for an electric fan


LonesomeSTX

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I have been planning to convert all our truck electric fans. I was hoping to build a standard wiring harness to work with all of them using common parts. I do not want to use a store bought fan controller because of their reputation for giving out. I believe I have found, what I consider, the best option for what I am trying to do. However, I cannot find a design that eliminates the probe that sticks in the radiator. I do not want to go that route. However, any switches I find either tie into the ECM or require some kind of special hardware or parts that are model specific. Any thoughts or suggestions of this?
 


LonesomeSTX

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I have looked at those. The challenge I am facing is getting them to work with the different trucks. I do not have a port to screw it into. Making one might be an option with some more thought. But before I go that route I wanted to see if there is something else out there I may have missed.
 

Bronco638

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I've been doing quite a bit of research on this (like you). In my (interwebz) travels, I thought I saw some type of controller where the temperature probe was actually slipped into the upper radiator hose, at the radiator. That sounds hokey to me.

I'm thinking of going with a Derale ("der-ray-lee") fan and probe-in-the-radiator controller. I can't seem to find anything else that's easier to install and has better feedback/ratings.
 

LonesomeSTX

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I saw that too I did not like it at all. It looked very flimsy. I have not seen any fan controllers or in radiator fan probes that are worth a shit.also, my way of thinking, if the OE did not do it that way that should be a clue.
 

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The e-fan and it's high amp relays are a separate system than the controller, and should be wired and fused that way.

Activating the high amp relay(s) is a low amp circuit and since this is a temperature sensitive system a temp sensor seems the best choice.
There are a few options available, factory has the luxury of building from scratch, which is why they don't use temp sensors inserted into rad fins, which does work.

Factory sensors tend to be in the upper or lower Rad hoses, some in the rad itself, the luxury of building from scratch :)

This how-to show various rad hose sensors/housings that are available: http://www.therangerstation.com/tech_library/volvo_electric_fan.shtml

I wouldn't use ECT sensor as that is part of the engine management system.
You could use the ECT sender(for dash board gauge) it is a simple resistance sender, gauge would still be connected and work normally.

Upper engine/rad hose temp would be 200degF normally, no fan needed, lower hose would be 15degF cooler 185degF
So you would want to trigger fan at about 210degF on upper or 195degF on lower hose
 
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LonesomeSTX

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Thanks for the link!
 

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Find a high limit off of a gas furnace you can get them that adjust to open at different temperature most of them work on 24 volts they will work on 12volts to you can get them to open on temperature rise or close
 

LonesomeSTX

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that is something I had not heard of. I will be looking into that thanks
 

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Why couldn't you get a T connector and stick a probe in where the instrument clusters sensor plugs in on the lower intake manifold?
 

LonesomeSTX

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I like the sound of that. Could you be a bit more specific though? I am not sure I quite follow.
 

Bronco638

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cp2295 probably means that the temp sensor threads into the intake with either 1/2" or 3/8" NPT (National Pipe Thread). So, remove the sensor to determine what thread size you have. Go to a good hardware or home improvement store and get a nipple and "T" fitting the same thread size as the sensor. Thread the nipple into the manifold and then screw the "T" onto the nipple. Now you have two "ports" into which temperature sensors can be threaded.

The JEGS part, that was previously linked, is 3/8" NPT.

If the hole in the intake is 3/8", I would suggest you use brass fittings, they won't corrode as quickly as steel will.
 
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RonD

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I wouldn't do that, the "T" idea, if it was a pressure sender it would be OK but the temp sender should be in an active flow of the coolant, the "T" would just have transferred heat not an active flow.
It would be very slow to respond to an overheating issue.

You could use the "T" idea on a heater hose, but it would need to be an active by-pass hose, i.e. coolant is flowing all the time.
If there is a valve to shut off flow to heater core then it wouldn't work.
If there was no valve(like my '94) or there was a By-pass valve(4 hose connections), then it would work.


You can use the existing temp sender as is but it would be a 1 speed trigger, and gauge would still be working.
Ford temp SENDER(not sensor) should have 75ohms cold and 1,000ohms hot.
Simplest method would be to use a relay and variable resistor on a wire added to sender.
Relay coil would get 12v with key on, it would be grounded via the sender, cold the relay would be closed so no power passing to 87A contact on relay.
As sender warms up resistance(ohms) gets higher, you would adjust variable resistor to a resistance that would lower power at relay's coil at high resistance and relay would open(87A is connected), triggering e-fan relays.
This is also a fail safe circuit for the most part, if circuit fails e-fan is on with the key

This would not effect temp gauge as resistance at sender is the same for its circuit.
 
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LonesomeSTX

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installing a port in the upper radiator hose it's starting to appeal to me. I did some more reading on that and it would appear, to be the best solution. But is it though?
 

RonD

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That was the most common factory location until coolant manifold or intake could be redesigned for a 3rd ECT sender.

Rotate housing so sensor is on the side of the hose, upper rad hose can get air in the top area, you want sensor in the coolant flow for true temp reading.

Lower rad hose is OK as well but.............if rad starts to clog up flow slows down so coolant cools off more, this could delay e-fan startup in an overheating event.
 

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