Cooling Fan Probs

I'm having a problem with my #2 (Passenger Side) Cooling fan not turning on. There is no voltage at the connector when #1 fan is running. I pulled the fuse and checked the relay. Both were fine. While the relay was out read 13.8 Volts across the relay terminals inside the box, so I know there is voltage there, which leads me to believe the problem lies between the relay and the connector. Are there any splices between the connector for cooling fan #2 and the relay box? Seems odd to me that a wire would fail...Just looking for some input before I go pulling wire out of the looms. Thanks in advance!

'96 Lumina
126k Miles

One (sub-cooling fan), only runs during A/C operation and overheat.

Try swapping the relays and see what happens.

There is a way to tell the ECM to turn both fans on from the diagnostic connector, but I don't remember how it is done.

Tried swapping the relays...no go. I pulled the original #2 relay and removed the case. I bridged two diagonal terminals (i forget which numbers) with a 9 volt battery(same two that would have contacted the 13.8 Volt source that I tested earlier inside the relay box. Before I attached my 9V source the other two diagonal terminals read Infinite resistance (open circuit). When I attached the 9V the switch closed and i read 0.3 Ohm resistance. So, when attached to the 13.8V in the car, the switch should be closing sending the power somewhere...I'm just not sure where...All i know is that it's not my fan:-P

you mentioned that one is a sub-cooling fan...on during a/c and over heating. i made a 300 mile trip this weekend. on the 150 mile trip to my destination i hit a traffic jam, temp guage read about 3/4 without the air on, when the car wasnt moving. when i reached cruising speed (55-70MPH) temp went way down, to about 1/3 or so. 3/4 of the way up on the temp guage seems high to me, it's not in the red, but it's never gotten that hot before...ever...and the second fan is not turing on at that temp, but like i said, i'm getting voltage in the relay, and the switch is closing, which seems like it's telling the fan to turn on...

Can you just shunt from there to the fan, and see if it comes on? By bridging the harness with a shunt, you could verify that the wiring is bad if the fan starts.

Make sure there is a good ground on that fan's circuit too.

If the fans work most the time the relays when made will turn on the fan connectec to it. Maybe i missed the part where you checked the fans already. If you turn you a/c on fan #2 should come on or have power to the wire that connects to it. Otherwise without the a/c on there will be no current. Fan motors run about 30$
Hope this helps.


gary