12v car fan status monitor - Page 2 - Electronic Circuits Projects Diagrams Free

**3v0** · 30th March 2008, 09:06 PM

Quote:

Originally Posted by Diver300

Who cares?

40 mph wind will cool a car engine so why worry?

I have seen a radiator fan windmill fast enough to make an indicator light glow. A fan is only needed at low speeds.

They OP is either paranoid or has an iffy fan.

Back in the 80's a friend and I set out for the Pennsic War in a MGB. The electric radiator fan windmilled for a few 100 miles and at some point the bearings gave up and it seized. When we hit Chicago stop and go traffic the fan tried to kick in. The fuse blew after melting a bit of wire. People who own MGs understand this sort of thing.

If we had an indication that the fan had frozen we could have avoided being stuck in traffic. The point is that you need to sense the failue as soon as possible. Only doing so a low speeds when the fan is needed can be too late.

mneary · 3rd April 2008, 04:00 AM

You can know everything with a voltage measurement across the fan.

If the fan has a reasonable voltage while in motion, it is windmilling. Very good.
If the fan has 12V (+/-) in traffic it is probably running. Pretty good.

If the fan has 0V while driving (no windmilling), Bad.
If the fan has 0V in traffic (fuse) Very Bad.

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3rd April 2008, 04:00 AM	(permalink)
mneary	You can know everything with a voltage measurement across the fan. If the fan has a reasonable voltage while in motion, it is windmilling. Very good. If the fan has 12V (+/-) in traffic it is probably running. Pretty good. If the fan has 0V while driving (no windmilling), Bad. If the fan has 0V in traffic (fuse) Very Bad.