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Spitfire Twin cooling fans on the Spit...

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Lionheart

Senior Member
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I installed two 9" cooling fans on my '77 "Rat Rod LBC" Spitfire.

I built a nifty control circuit using a comparator chip and a couple of relays...I had hoped to tap into the temp gauge sensor to provide the thermal sensing. This did not pan out, though...the voltage at the sensor seems to be all over the place (gauge works steady).

Does anyone know if the voltage to the temp gauge is "chopped" by the (voltage conditioner)? I really have no idea what that thing does...guess I thought it was a smoothing filter. Can I connect it direct to 12V?

I have a thermistor to use as an alternative...where to mount it kinda confounds me. I also have a '79-80 thermo switch...it is far too large in diameter to mount in the water jacket.

BTW...the goal is to have the two fans work with "staged" control (one comes on at ~180...other comes on at ~195).

Len
 
Lionheart said:
...Does anyone know if the voltage to the temp gauge is "chopped" by the (voltage conditioner)? I really have no idea what that thing does...guess I thought it was a smoothing filter. Can I connect it direct to 12V?
Click to expand...
Connect the gauge to 12v directly? No. The voltage stabilizer "controls" both the fuel and temp gauges, so they're calibrated to +/- 10v or thereabouts and should not run on a full 12v. Although MAYBE if you used an early sender (not sure if all Spitfire temp gauges were voltage stabilized or not, but earlier Heralds were NOT)....
 
OK thanks Andy. I guess I have two paths to pursue:

1. Find a different (smaller) thermo pickup to add to the water jacket somewhere.

2. Find a way to mount the tiny thermistor that I have.

Some aftermarket fan controllers use surface heat from the radiator; I'd prefer to have it in the water for better response to changing temps.
 
Lionheart said:
I built a nifty control circuit using a comparator chip and a couple of relays...I had hoped to tap into the temp gauge sensor to provide the thermal sensing. This did not pan out, though...the voltage at the sensor seems to be all over the place (gauge works steady).

Does anyone know if the voltage to the temp gauge is "chopped" by the (voltage conditioner)?
Click to expand...

I finally found out why the voltage stabilizer output was "all over the place". The voltage stabilizer is actually a mechanical regulator, just like an old fashioned voltage regulator which uses a bimetal strip wrapped by the current-carrying wire to make and break connection.

So, in an effort to get my electric fan setup working, I converted the stabilizer to solid state.

I used an LM-317 adjustable voltage regulator and two resistors to produce a steady 10v supply. Even built it into the original stabilizer housing:
ModifiedStabilizer.jpg

Now that I got that sorted, the fan controller circuit that I built is not doing what it's supposed to. I may just break down and buy a fan controller, like normal people.

I guess the message here is that if your stabilizer goes out, you can fix it with about $1 worth of components. Let me know if you need more info.

Len
 
Very nice, almost identical to what I did. If you use a 7810 chip, you don't need the additional resistors. I soldered the voltage controller to the case so that it would act as a heat sink.
Yisrael
 
70herald said:
Very nice, almost identical to what I did. If you use a 7810 chip, you don't need the additional resistors. I soldered the voltage controller to the case so that it would act as a heat sink.
Yisrael
Click to expand...
I was just too impatient to order & wait for a 7810...I had an LM317 left over from another project.
As far as soldering the tab to the case, the LM317 has the Vout on the tab. I just pop-riveted it to the phenolic piece. I didn't measure the current flow for the gauges, but I'm hoping that current (i.e. heat) won't be an issue.

I am really regretting now that I got rid of my breadboarding equipment many years ago. (Refer to fan control ckt mentioned above.)
 
Lionheart said:
70herald said:
Very nice, almost identical to what I did. If you use a 7810 chip, you don't need the additional resistors. I soldered the voltage controller to the case so that it would act as a heat sink.
Yisrael
Click to expand...
I was just too impatient to order & wait for a 7810...I had an LM317 left over from another project.
As far as soldering the tab to the case, the LM317 has the Vout on the tab. I just pop-riveted it to the phenolic piece. I didn't measure the current flow for the gauges, but I'm hoping that current (i.e. heat) won't be an issue.

I am really regretting now that I got rid of my breadboarding equipment many years ago. (Refer to fan control ckt mentioned above.)
Click to expand...
The 7810 uses the heatsink as the ground. As far as heating, with two gauges attached, it doesn't even begin to warm up no less become hot. I think that the LM317 has a similar rating so you should be fine.
 
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