Hey Carguy,
Where would the other sensor be located?
I changed the one on top of the motor near the thermostat housing.
I have looked in the Haines book and do not see another one.
Please help!

 

if the fan comes on when u unplug the sensor u have the right one. using a jumper wire u should be able to connect the two wires or if one wire, ground it and the fans should come on. (this is from a 93 3.4 so take it as that) test the yellow wire for dc volts, should read 5 vdc. if not u have a bad or grounded wire or ecu is faulty. the sensor itself can be tested be ohm resistance.
ECT Temperature vs. Resistance Values

∫C ∫F Ohms
100 212 177
90 194 241
80 176 332
70 158 467
60 140 667
50 122 973
45 113 1188
40 104 1459
35 95 1802
30 86 2238
25 77 2796
20 68 3520
15 59 4450
10 50 5670
5 41 7280
0 32 9420
-5 23 12300
-10 14 16180
-15 5 21450
-20 -4 28680
-30 -22 52700
-40 -40 100700

 

Not sure about a V6 but on the 5.0 and 5.7 the sensor that controls the fan is on the passenger side head between #6 and #8 plug. You can check the fan by unplugging the wire, turn the ignition to "on" and ground the wire. If the fan comes on, the sensor is fubar. Usualy the sensor by the stat is for ECM coolant readings and the sensor in the driver side head is for the gauge. V6 might be the same, worth taking a look.

 

thats odd. lol. on the 4th gen 5.7 the sensor on the passenger side block is the knock sensor.

 

Carguy,
I looked on the passenger side and only found one sensor.
It is located just in front of the starter and does NOT look like a coolant sensor. It is a lot bigger and appears to be the knock sensor.
When I unplug the coolant sensor on the top of the motor, the fan comes on and the engine light pops on. I plug it back in and the light and the fan both go off!

 

fan switch looks like this. almost the same as a knock sensor. but not. lol

 

does the car seem to be running rich, that could be an indication of a bad temp sensor.

 

On the 3.1 cars the ECM controls the cooling fan relay via input from the engine coolant temperature sensor. The ECM will NOT turn on the fans until 229-230 degrees. The first step is to connect a scan tool and pull up the ECT (engine coolant temp) and observe it while sitting in gear idling...when YOU think the car is running hot, look at the coolant temp on the scanner....if it is not greater than 230 degrees the ECM does not think so and has not requested cooling fan operation. If it IS above 230* and the fan is not on, THEN there is a problem.....However you pretty much already verified the motor, the relay, the wiring, etc.....you said it runs with the coolant temp sensor unplugged...THIS is normal...it is a fail-safe in the programming...if the sensor wiring get cut, or unplugged the ECM sees that as 40 BELOW zero....and it knows this is unlikely, so it runs the fan just in case the wiring has failed.

If you watch the scanner temp and it DOES get above 230* and no fan, let us know and we will go from there. On a few V-6 3.1 cars I've seen, there was another switch above the starter that shows up in the wiring diagram....but I have yet to see one that actually had it installed.

T@IP

 

the post above mine is very informative. if you dont have access though to a scan tool, you can just rewire the fan to an on/off switch. i did that with my car because the fan didnt come on until at least 240 degrees.