I am a cheapskate and rather than something fancier (more expensive fan controller) had previously been using the temp sensor to directly drive the fan relays directly. It does work to keep the truck cool but is imperfect by my estimation.

The problem I was having is excessive fan cycling as the system cools after shutting the engine down. The engine is staying cool just fine. I didn't really notice the excessive fan cycling happening when I'm driving around but they were doing it when I shut off the engine. It is annoying and prematurely wears out electromechanical relays.

Maybe someone else here finds this cool and useful as I did.


I bought a couple of these things to try one as a fan controller and it's pretty cool.

I'm using it in it's "triggered, off delay" mode with about a 5 minute delay.

All this thing is doing is turning on the relays for fans when it sees the signal from the temp sensor but it keeps them running for about 5 minutes longer after the temps sensor signal goes away. I had to play with the timing a little to find a "delay" long enough to stop the fan cycling after engine shutdown but this little device can accommodate quite an impressive range of delays.

With the timer, the fans just keep running for around five minutes after the engine is shut off, before they shut down, but there is no longer any repeated fan cycling occurring.

Now the fan control works as well as any efan equipped car I've ever owned and the cost was very low compared to some control schemes I looked at. I have the 10 ish dollar temperature sensor and this 16 dollar timer now controlling a couple 10 dollar relays. About the only other thing I may do at some point is convert to some solid state relays to try and reduce the likelihood of relay failure.

Oh yeah another thing about this little timer. I emailed the company about it. It is all solid state, ie no electromechanical relays in it to wear out. They said it is rated for operation between -40-100C and would be perfectly happy under the hood of my truck. In my case it's mounted inside a accessory fuse/relay box so is fairly well protected, The timers I received look a little different than in the amazon photo in that they are completely over molded in some kind of plastic, ie no way for moisture to get in. I have confidence this littley guy should be able to live a long life and they seemed to indicate it would be fine in this application.

 

Interesting and seemingly effective way to solve your problem! Myself, i run a temp sensor based triple relay controller that, unfortunately, is no longer available. Pretty good setup though. My fan is a 2-speed and the low speed comes on at 180, high at 195.

 

Hmm. Variable speed sounds kind of cool. Maybe I'll think about trying integrating that into my control scheme after I've made the conversion to solid state relays.

There are some very low cost 12V temp controlled pwm modules available online one could possibly integrate into a control scheme like mine. Here is an example that might work but which would need some kind of an enclosure.
A PWM controller like that would definitely require me to do the conversion to solid state relays. Ensuring proper protection of a solid state relay in a inductive load application would be critical for the SSR survival.

I'd also need a second temp sensor which would work with that type of control.
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