Electric fan thermostat

[robert]

I had an idea recently that may be of interest (sorry if it's an old idea but I've never come across it before). My roadster came with the usual mechanical fan thermostat with the semi-rigid tube type sensor similar to a domestic oven. Anyway it stopped working and rather than buy a new one (!) I set about designing an electronic version using a small thermistor as the sensor. Then it occurred to me that the engine already has one so why not use that? The temperature gauge passes current through the sensor so all that is required is to monitor the voltage on the sensor and turn on the fan when it reaches some threshold (about 3 volts on my car). I've mounted my new unit where the old one was near the radiator with an extra wire to the temperature sensor, but it would probably be even better behind the dash picking up the sensor voltage from the gauge - much neater than the old type and cheaper too. It seems to work fine. Anyone heard of this before? Is there any reason why I shouldn't use the engine temperature sensor to operate the radiator fan?

[Dane_Rescueman]

Re: Electric fan thermostat

Hi Rob,

I have the antique bulb and capillary tube [adjustable] thermostat. I like the sound of your idea but I just worry that you will be using some sort of voltage comparator chip. This could well be misled by the "bucket brigade" instrument voltage stabiliser if you have one. My ford based system has this extremely annoying item fitted.

Good luck,

Dane.

[robert]

Re: Electric fan thermostat

Good point, Dane. Luckily I don't have a voltage stabiliser but you are right, that would upset it.

Rob

[amalgamated users from prior forum]

Re: Electric fan thermostat

Message originally posted by: Malcolm Sherratt
Rob, dammed clever fix / mod, You have removed an element of "belt and braces" from your cooling system, if you have any fault, wiring temp sensor etc there is no back up,say for example your temp sensor goes faulty,normally this would only be a lack of information but with your system you will not have any fan either, I am sure that if you thought about it a canny chap like yourself could work around this, maybe fit a second temp sensor for the fan or similar?
best regards
MalcS

[philcoyle]

Re: Electric fan thermostat

Morgan Motors have a small switch fitted in the radiator 19mm. hole reqired.Cheaper than your capillary tube type sensor just use a bit of plumbing knowledge,and fit it in your top hose,mine works a treat.