I've have EL thermofans in my EB Falcon controlled by a switch in the thermostat. Sometimes the fans will keep turning on/off i assume because the switch is at the temp where the fans are switched. This causes the voltage metre to jump all around the place sometimes over 16v and usually down to around 12v. Is this going to cause any probs or should I just not worry about it? The only issue is at night time my headlights will dim up and down when this happens but I worry about my electrical gear such as stereo. How can i rectify this problem?
Youll probably find most thermofans are very hungry for current and the only way to avoid such a drain on your battery even with the motor running is to upgrade the alternator to a higher capacity. (12 Volt should be ok
Also as the fans are switched off (be it by switch or thermostat), the fans are inductive which produce a huge back EMF (High Voltage) when disconnected. The only way I can see this may be corrected is by using a diode in reverse bias across the input to the fan. This is only in theory.
However as Slayer said, should be running through a relay and should be sourcing its power closest toward the battery. If its getting power from wiring that is not desighned to carry such current, it will cause the voltage to jump around due to the voltage drop across the wiring.
Thermos draw close to 30A, i used to be able to flatten my batt with stereo, hesdlights, demister and thermos on while i was driving
Bigger altinater may help
Have you driven a Ford....lateley?
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I dont think alternator is the problem as the voltage is fine when everything is running (thermos, stereo, lights,etc) but when the fans cut off the voltage then jumps around. Maybe the relay isn't coping so it cuts in and out after running for a bit? Dunno...
You say you have the fans "controlled by a switch in the thermostat". What exactly does this mean? Do you have a proper thermostatic fan controller, or is it something else, as they should not cycle on and off in such a way.
So you have the relays wired to the temp switch right?
If this is the case, you need to pick up a proper thermo controlled fan switch, as wiring it to the standard temp switch won't work properly, as you've found out.
Davies Craig make the correct switches for about $60.
No, that looks like a stand alone switch for the fans, the lil sender below it is the one for the gauge.
Lindsay, can you draw up a rough diagram of how you have it all connected and email it to me or post it here,
Should be able to sort it for you.
Also, I also have electronic switches available for the elect fans, which piggyback off the temp gauge sender, and they have an adjustable set point instead of a fixed temp at which the fans turn on.
They work really well.
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