Hi all! Got a problem with my 95 Camaro 3.4L. The radiator fan is not turning on at any temp level. I read somewhere that the fan should turn on at 220*, the engine temp on my car rose to about 260* yesterday and I opened the hood to see if the fan is working. My Haynes manual said check the fan, relay and temperature sending unit. Fan worked when applied with 12V directly, fan relay tested good, no continuity between pins 1 and 4, unless voltage is applied to pin 5 and pin 2 is grounded, then continuity is there. I also checked the socket of the relay, Haynes said socket 1 shoud always be powered, socket 5 powered only when key is in the "ON" position. Checked out ok except socket 5 had very low voltage, not like socket 1 which had ~12V. Haynes did not mention ho many volts each socket had to have. I then checked the temperature sending unit. Haynes manual said that resistance of the sending unit should be ~1300 ohms when engine is 100* or below and around 55 ohms when 260*. I did not get this and am assuming the sending unit is defective. My question is, will a defective sending unit not turn the fan on? The temp guage inside the car is working fine, tested it also by grounding the sending wire. The guage went to full swing, indicating that the wiring and he temp guage are both working. Need help as I just had my engine rebuilt and don't want to mess it up due to overheating. Any suggestions? TIA.[/align]

 

The ECT sensor sends temp data to the PCM. Depending on the temp data the PCM orders the fan ON by operating the fan relays. The problem could be the temp sensor, wiring between sensor & PCM. Wiring between PCM & fan relays, bad fan relay, wiring problem between fan relay & fan motor, no power to relay contacts (check fan fuse and wiring between fan fuse & fan relays). Get a voltmeter & have fun. Quick check, disconnect plug from ECT and connect a 50 to 100 ohm resistor between the two wires. If fan goes on all wiring is good & sensor is bad. Do not short out the wires directly as it may damage the PCM.

 

z28pete, thanks! did that check with a 100 ohm resistor and fan turned on. $14.99 later and replaced the ECT and all is working now. thanks again.