Radiator Temperature Sensor

fastd · #1 (**permalink**) 06-06-2021, 04:56 PM

Anyone have suggestions for a temp sensing fan switch turn off, i.e. a switch to keep the fans running after the ignition switch is turned off until the radiator fluid cools down?

I looked around and was surprised I didn't find an easy answer...?

patrickt · #2 (**permalink**) 06-06-2021, 05:44 PM

Every ERA I've ever seen had a thermostatic switch in a tube that linked to hoses at the bottom of the radiator. The switch sends a ground to the fan relay on the firewall. The manual says the switch is from 1980-1984 VW Rabbit or Jetta #823 959 481/75.

TexasSnake · #3 (**permalink**) 06-06-2021, 08:02 PM

Speedway, Jeg’s, Summit all sell a adjustable temp fan relay switch for about 30 bucks. They are easy to install and work great.

strictlypersonl · #4 (**permalink**) 06-07-2021, 06:41 AM

As Pat said, every ERA since 1988 had a thermo-switch in the lower hose connector that did exactly that. If it's not working, check the fuse and the fan relay.

kitcarbp · #5 (**permalink**) 06-07-2021, 07:50 AM

If you are looking for a modern cooling fan controller that can control 1 or two fans and fully programable after engine off with user defined fan turn off times, this new version from dakota digital even has bluetooth connectivity to make programming even easier. Im about to pull the trigger on this to lower my under hood heat soak temps after key off. But I have no idea on its reliability, its aftermarket.

Check it out
https://www.dakotadigital.com/index....od/prd1207.htm

fastd · #6 (**permalink**) 06-07-2021, 11:58 AM

These are all great options; thank you.

FYI, this is for another car, not my ERA (that sensor/set up works perfectly!)

era626 · #7 (**permalink**) 06-07-2021, 12:37 PM

please explain this... am I missing something? running a fan after the car is shut off is only cooling the coolant in the radiator, what's the point? my fans shut off when i turn off the ignition with no issues.

Austin_Snake · #8 (**permalink**) 06-07-2021, 01:19 PM

So I installed a fan wiring kit from Painless Performance and came with a switch that operated at a set temperature range. They offer different ranges so you can get your fans to run at the correct temps. Sensor just screwed in where the existing temp sensor went.
Though I am not sure why you want it to run after the engine turns off. Where I live it gets pretty hot so when I'd get home the fan would run way too long and eventually drain the battery. The water is not flowing and the block is just soaked in heat. I rewired it to my Ignition so it goes off with the key.
Good luck,
Richard

fastd · #9 (**permalink**) 06-07-2021, 02:28 PM

Quote:

Originally Posted by era626

please explain this... am I missing something? running a fan after the car is shut off is only cooling the coolant in the radiator, what's the point? my fans shut off when i turn off the ignition with no issues.

If I'm at the track or as I am testing the car, I'd like to have the fan run after the ignition is turned off some times. Right now I have a switch to power it but I'd like to have some type of timer on there in case I forget to turn it off manually.

cycleguy55 · #10 (**permalink**) 06-07-2021, 02:50 PM

Quote:

Originally Posted by fastd

If I'm at the track or as I am testing the car, I'd like to have the fan run after the ignition is turned off some times. Right now I have a switch to power it but I'd like to have some type of timer on there in case I forget to turn it off manually.

It seems you have a couple of options, without getting into semi-exotic, programmable controllers, either:

something similar to the ERA setup, with a temperature sensor in the lower radiator hose; or
a simple timer relay that will run the fan(s) for a fixed interval.

The former is well-proven and will run only until the sensor determines the set temperature has been reached. The latter will run for that fixed interval, even when not necessary (e.g. a cool day).

I'd lean toward setup #1.

Regardless - here are couple of timer setups:
Hella 996152131 - Hella Adjustable Time Delay Relay (adjust time with DIP switches on top of relay): https://www.summitracing.com/parts/hla-996152131
Timer Relay, DROK 0.1s to 999min: https://www.amazon.com/DROK-Automoti...ct_top?ie=UTF8

era626 · #11 (**permalink**) 06-07-2021, 02:55 PM

I have my ECU (mega squirt) control my puller fan and a switch on my dash to control the pusher fans. This seems to work well. Again I do not understand why the fan needs to run after the motor is turned off. All it is doing at that point is cooling the radiator...
The other day here in NOR CAL it got 100 degrees and my car never got above 80c i guess I have been blessed by the FE gods...

Randy Rosenberg · #12 (**permalink**) 06-07-2021, 03:26 PM

After a long, hot, run, I'll turn my fans on after turning off the ignition. The heat from the block is absorbed into my carb and sometimes caused the fuel to boil. By circulating air under the hood (pushing air thru the compartment) it helps to prevent this problem. This is also happens if/when I stop for gas during a long, hot run. I only run the fan for maybe 5 to 10 minutes, or during the length of time it takes to fill her up. Many times, I click the fans on about 1/4 mile from home just to add in this shutdown cooling.

strictlypersonl · #13 (**permalink**) 06-07-2021, 03:38 PM

Quote:

Originally Posted by era626

please explain this... am I missing something? running a fan after the car is shut off is only cooling the coolant in the radiator, what's the point? my fans shut off when i turn off the ignition with no issues.

If the thermostat is open, water will automatically "thermosiphon" through the system, including the engine block. That will help eliminate boiling in the engine's hot spots.

eschaider · #14 (**permalink**) 06-08-2021, 03:21 AM

There is a guy that goes by the name The Auto Cool Guy at the website autocoolguy.com. His real name is Darryl Dashiell. Darryl is a Vietnam Vet and he builds some of the nicest electric fan and water pump controllers I have ever seen.

He built a custom unit for me that I ordered through Hollister Road Company. Sadly, the Hollister Road Company owner, Dave Chapman, passed on a couple of years ago.

This is what my unit looks like;

This was a custom build to control an electric water pump and a MK VIII Lincoln electric fan using Pulse Width Modulation (PWM) control. The fan was the biggest challenge because it drew a little north of 100 amps on a cold start. Sort of like a starter motor, unbelievably, but a fan! The high current draw would kill just about anything that was commercially available at the time.

Darryl built this unit with a soft start capability that turns the fan and pump on at a very low speed initially as the temp sensor sees the coolant temp rising both seamlessly increment in speed to maintain your target engine temp. The start temps are settable with a screwdriver and separate dashpots.

As the vehicle comes up to road speed and the airflow through the radiator is adequate to cool the radiator the fan slowly ramps down to a lower speed or zero depending on air flow across the radiator and where you set the coolant on temp threshold.

When you shut the car off the fan and water pump run on for two minutes or so after engine shut down to eliminate any hot spots in the engine.

The unit is very easy to configure and use. When you install it you remove the mechanical thermostat because it is no longer used. There is an electric coolant temperature sensor that takes the place of the thermostat and informs the controller of the coolant temperature so it can determine how fast to drive the water pump and the fan to maintain your target engine temp.

Very nice package. I suspect 99% of you guys don't / won't use an electric water pump so that part is probably a not so necessary element for your installations.

Check out his website he has a gazillion variations of just the basic fan controller system and they are all his design and made by him right here in the US and if that's not enough he's also a Vietnam vet!

Ed

era626 · #15 (**permalink**) 06-08-2021, 03:33 PM

Quote:

Originally Posted by strictlypersonl

If the thermostat is open, water will automatically "thermosiphon" through the system, including the engine block. That will help eliminate boiling in the engine's hot spots.

yes I agree if the "thermostat is open" the water will flow, but i am asking about the fans running after the motor is turned OFF. At that point the fans are only cooling the radiator. I see what Randy is taking about however about a little air flow in the engine compartment. I did not really think about that.

eschaider · #16 (**permalink**) 06-08-2021, 03:55 PM

Quote:

Originally Posted by era626

yes I agree if the "thermostat is open" the water will flow, but i am asking about the fans running after the motor is turned OFF. At that point the fans are only cooling the radiator. I see what Randy is taking about however about a little air flow in the engine compartment. I did not really think about that.

ERA626, (apologies I forgot your first name!) check out the controller I wrote about in Post #14 above. It does everything you want and more. The auto cool guy offers other units with a reduced set of features or a different set of features that may better fit your needs.

Ed

era626 · #17 (**permalink**) 06-08-2021, 04:21 PM

ed, I am fine my car works great. It never goes over 80c... I thing the guy who made this post it the one who needs it... ty

strictlypersonl · #18 (**permalink**) 06-09-2021, 06:54 AM

It works
https://en.wikipedia.org/wiki/Thermo...Engine_cooling