[Mgs] thermistor

PaulHunt73 paulhunt73 at virginmedia.com
Wed Jun 7 03:00:32 MDT 2017

A thermistor will normally give a resistance that varies with heat, and 
needs some threshold device to switch a relay or fan.  Without the threshold 
device relay operation can be erratic, or switch on and off repeatedly.  The 
threshold device causes the relay to switch on cleanly at a given 
temperature, and switches it cleanly off again a few degrees lower.  The 
other advantage of the threshold device is that as long as a thermistor has 
the usual fan operation temperature of typically 90C within its normal 
operating range the point at which the fan cuts it and out can be adjusted 
with a variable resistor.

Factory systems use a bi-metal contact that pings closed at a given 
temperature, and pings open a few degrees lower, to give a clean electrical 
signal to either fan or fan relay.


----- Original Message ----- 

I was using a thermistor on my radiator to sense temperature and then ground 
a relay to turn on a fan.  After 25 years, it doesn’t trigger the fan and I 
can’t find the notes for the specs.   Anyone using a similar set up who 
might have a part number for one that might work?   I mounted it on engine 
side of the radiator...

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