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Electric radiator fan controller

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1510641 by Tonyfixit The sensor cable is only about 18" long, I guess I could order a longer K type sensor for another $1.
According to the ad, that unit uses a thermistor rather than a thermocouple. You should be able to attach longer wires if you want.

I think I see a voltage regulator on the board, so noise on the power shouldn't be a problem. If noise on the pickup line becomes a problem, you could try using shielded cable instead of a plain pair; but I think it's unlikely. Easier to just turn the hysteresis up a bit.



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

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TR3driver Randall Y
Confusion, Los Angeles, USA   USA
In reply to # 1510734 by Tonyfixit No, the fan is set to come on at a temp significantly higher than the thermostat rating.

The thermostat sets the minimum engine operating temp.
Definitely true.

But I feel there is still some small advantage in putting the sensor on the output side. That way, the fan won't run when the airflow through the radiator is just barely adequate to maintain the set temperature; and you can put the fan setting closer to the thermostat setting (or even below) without having the fan run all the time. I have mine set to come on when the return from the radiator reaches 190F and that works out very well IMO. The rise on the gauge is very minimal, but the fan only runs when I'm stopped for a time, or moving very slowly. (I used an automotive style temp gauge sender from the parts bin; and mounted it in the water pump intake.)

The two features I would like to add are a way to keep the fan running for up to 5 minutes after the car is shut off; and maybe a PWM mode (instead of simple on/off).



Randall
56 TR3 TS13571L daily driver
71 Stag LE1473L awaiting engine rebuild
7? Stag awaiting gearbox rebuild

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
I may just play with the probe location, and see which works best.

Dave, if you are going for a dash mount display, this model may be easier.
https://www.ebay.com/itm/DC12V-W1218-Red-Blue-Thermostat-3-Digit-NTC-Probe-Controller-Replace-W1209WK/182739804969?hash=item2a8c242329:m:mPkI3uqfAeTbO2-T8IoIZew

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Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, NV, USA   USA
In reply to # 1510801 by TR3driver
In reply to # 1510734 by Tonyfixit No, the fan is set to come on at a temp significantly higher than the thermostat rating.

The thermostat sets the minimum engine operating temp.
Definitely true.

But I feel there is still some small advantage in putting the sensor on the output side. That way, the fan won't run when the airflow through the radiator is just barely adequate to maintain the set temperature; and you can put the fan setting closer to the thermostat setting (or even below) without having the fan run all the time. I have mine set to come on when the return from the radiator reaches 190F and that works out very well IMO. The rise on the gauge is very minimal, but the fan only runs when I'm stopped for a time, or moving very slowly. (I used an automotive style temp gauge sender from the parts bin; and mounted it in the water pump intake.)

The two features I would like to add are a way to keep the fan running for up to 5 minutes after the car is shut off; and maybe a PWM mode (instead of simple on/off).

Add a second sensor and fan. That's what modern cars do. Small fan for the top and large fan for the bottom set about 20 degrees apart.

Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
So I tested the controler tonight, just on a bench.
When powered the led display shows the sensor temperature (in this case ambient room temp ) you press set, then you can put in the desired target temp, or temp the fan should kick in (for testing this was 50c. All temps are in Celsius, sorry USA ;-) ) then you press set once again. Display reverts to sensor temp.

As the temp to the sensor rises a few degrees above the target temp, the relay closes with a nice click, and a red LED light comes on to show the fan would be running.

When the temp falls to below target (precisely) the LED goes out and the relay is open (no current )

Great, it works well. But, does the unit remember the target temp after the power is off?

I did not check this, but I suspect not.

If that is the case, it will have to be powered via the battery (brown wire) via a low amp fuse. Not a big deal, kind of like the programming of a car radio. The fan could still be ingnition powered.

If you did not do this, you would likely have to re-set the program every time you started the car :-(

clshore Carter Shore
Beverly Hills, FL, USA   USA
If the settings are not saved on power off,
hook up a 9v battery with some isolating diodes as a backup.

Doug in Vegas Avatar
Doug in Vegas Douglas D
Las Vegas, NV, USA   USA
I got one of those cheap HF battery maintainers. I then cut off the alligator clamps and hooked up a cigar lighter plug.

The cigar lighter socket is always powered so all I have to do is plug it in when I park.

....also saves having to hear, "What's wrong with it?" because the hood is up....

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
The static draw is only 35 milli amps, I'll probably wire it to the car battery**. Even though I have a battery isolation switch, if I do need to reprogram it after disconnecting the battery that is very easy and takes about 10 seconds.
There is also an overheat failsafe where if the heat goes out of range of the device, the fan cuts in anyway.

The built in relay is just a switch, so the fan itself can be powered by an igntion controlled circuit.

SpiTazz72 Avatar
SpiTazz72 Bryan H
Magnolia, TX, USA   USA
Once again good info here. I just bought an electric fan for my '72 Spitfire with an electronic relay/thermostat and will try to get it installed this weekend. I imagine I'll gain about 5 HP by removing the engine driven plastic fan..... But then I wake up. smiling smiley

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, BC, Canada   CAN
I have been playing and finding out more about this little gizmo.......wow


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