trying to wire up my temp control relay for my electric cooling fan.Cant figure the darn thing out.Bought at my local NAPA.Directions say to wire the red wire to positive side of battery,the yellow to an ignition source or something with constant power and the black to a ground.DID THAT!!This is an adjustable control from 90 degrees to 240 degrees.I heated the motor up to 185 and still no cooling fan.Supposed to be factory set at 160 so I turned it way down and still no fan.I wenty back to NAPA and changed out the relay today,tried it and still nothing.

What does the temp sensing part look like is it a probe or is it a screw in? If you have a part number that may help also.

Either way, try putting the sensor in boiling water with the key on and engine off to see if you just didn't get the sensor hot enough to ground the relay.

Another thing to do first is, check to make sure you have proper voltage and ground on your relay wires.

The red will be to the relay contacts to power the fan. The ign sense will be to power the relay when the temp sensor is up to temp. Tke the unit and connect both yellow and red to a battery with ground and put the sensor in hot water in a pan (using a small battery) and heat the water until the fan turns on. Measure the water temp and see if it's whacko.

Also meaure the voltages on the yellow and red to ground to make sure the relay is powered correctly. The yellow, of course, should only be 12 volts when the ignition is on. Make sure you have a really good ground and check it with an Ohm meter/continuity tester.

Chuck

Most sensors supply a ground when activated. Connect pin 86 on the relay to switched 12V. Connect pin 85 to the sensor. Connect pin 30 to 12V constant. Connect pin 87 to + side of fan. Ground the - side of the fan to the chassis. This will activate the relay when the sensor reaches the correct temp. If for some reason you sensor supplies power it will have two wires. You will still wire it the same way except one wire on the sensor will go to switched power and the other will go to pin 86 and then pin 85 will be grounded. To test your wiring connect pin 85 to ground and pin 86 to power this will activate the relay and if your fan is wired correctly it will turn on. Also if the sensor is supplying ground you cannot wrap it with Teflon tape it will not be able to conduct the ground from the engine block. The polarity on pins 85 and 86 does not matter as long as they are opposite. More info on relays http://www.6066gmcguy.org/BoschRelay.htm

... Also if the sensor is supplying ground you cannot wrap it with Teflon tape it will not be able to conduct the ground from the engine block...

This sounds like your problem. Use a test meter to verify the sensor is grounded to the block. If grounding the wire that goes to the sensor turns on the fan then either the sensor is bad or not properly grounded.

thanks to everybody for the help.I went and checked the probe sesor with an ohm meter and had very little resistance.Back to NAPA for the 4th time!!Changed out the unit and rewired everything back thru my wire loom and SHAZAAM!! worked slicker than goose s###.Thanks again everybody.