Hi Bosox last year I came to canada to study from IRAN, and I bought A ford contour 97 ( I even did not know the name of the car when I bought it, it was in a good body shape and had gentle owner!! so I bought it! and I know it is good car!), I had the same problem, exactly the fan did not come to work until the gauge pointer reached to L, I have worked on cars for more than ten years, I searched trough internet and this site, I found that this is a common problem and some people even changed the sensore, and nothing changed. this is a broblem with design of the sensor.Yea, I took them out of the board and tested them... Apparently they were two different patterns
I soldered them back in and my fan now comes on at the L, when before it would not come on at all :shrug:
My car is cursed :blackeye:
I do not remember which internet site but I got the idea through internet.
here is what I did.
You know that PCM comands the fan to work according to the resistance of the temrature sensor on the thermostat housing! as the engine gets warmer the resistance of sensor decreases for example according to auto zone site when tempratur is 90C the sensore resistance is 2.80 Kohm, when the temprature reaches 110C the resistance is 1.55 Kohm, (may be at some places here the PCM command the fan).
we make a trick to PCM! so when the tempature is for example 95 we make PCM to feel like somewhere around 105! so commands the fan to come to work sooner!!
to do this I add a Resistor to temprature sensor in paralel way. the total resistance is calculated by simple formule 1/Rtotal = (1/r sensore)+(1/r paralel)
at the time( about six month ego) I borowed my land lord multimeter! and came up with 12 Kohm resistor, I think you do not need high power resistor ( not sure) because I remember there is about 5 volts passes through sensor (simply measure itwith multimeter) so regarding to
Power (w)= volt*volt(v)/R(ohm) or P=vI
by measuring current and voltage determine the power of required resistor (P=VI) you can buy resistors from television and other appliance repair shops they are very cheap! less than a dollar! I recammand buy some resistores like 11 11.5 12 Kohm and put them on the car and look how sooner the fans comes to the work. then choose the right one
you need usual resistor but at the time I was fortunate and bought 20watt, 12.5 ohm heat resistant resistor (only 11 and 12.5 ohm was available in the old electronic shop near the room I rented, I tried both 12 Kohm worked better)just bare two wires going to sensore and connect the wires from resistor( sold two wire to resistor first),
so PCM reads less resistance from sensor
the problem here is that all the time PCM reads less resistance from sensor and when the engine is cold it does not start well ( you need to try two or three times) what I did there are some switches for woodfire place which with increase of temprature they close the circuit of fire place fan (it comes to work) and with decrease of temprature (when there is no fire in the fire place or you can imagine when engine cools down!!) they open thecircuit they come 45C and about 75C from ALLTEMP Company (nearly all the shopes which repare fire places have them) I added one of 45C degree of these swiches serri to the resitor and clamped it with a spring on the upper radiator hose ( I reccamand 70C degree it is better, at the time it was not available at the store I bought). so when the engine is cold less than 70 lets say ( in my car less than 45) the addes resistore is out of circuit like there is no resistor and pcm reads sensore resistance and engine starts well in any condition, when engine warms up and the thermostat opens lets say 85C the switch close the circuit and the resistor comes paralel to sensor switch and pcm reads engine temprature a little hotter that what it is actually so commands the fan sooner.
my car works great and the temprature gauge is allways at the begining of the M and as soon as it reahes middle of the M fans come to work, I think it is a little too sensible may be i need a more resistant resistor! but any way for me it works good and no problem at all,
the only thing is that the check engine light of my car was on when I bought it last year! and it is still on! ( student car!) I do not know if this modification can make the check engin light on because of sensore out of range resistance ( actually it can not be out of range because it modifies sensore resistance just for some tenth of Kohm which are still in range but at different tempratures of engine)
it can even help fuel consumption as PCM reads higher temprature and adjusts fuel mixture leaner ( the consumption of my caris realy low ).