Cooling fans

[Headman]

Has anyone had problems with the cooling fans on a 96 Lumina?
Let me explain my situation.
Just completed a valve job on a 96 Lumina with the 3.1L engine. Neighbors son decided to melt down the engine before he completely stopped driving it.
Things done to engine.
Valve job and surface.
New coolant sensor in manifold.
New water pump.
New thermostat.
New cam position sensor.

Problem is that the passenger side fan motor never comes on. Left side will come on if you turn on the AC. I have checked all fuses, and relays and they are good. Fan motor on passenger side is good. If I apply direct 12 volts to the motor it comes on. My crappy Haynes manual states that the ECM can be bad and is not delivering a signal to turn on fan.

Any ideas?

[Retardo]

From what I have heard, 3.1 engines are stock at 195*F. The primary fan (which is the one on the drivers side) is supposed to come on when the AC is running (cools down the freon, which is VERY hot under compression), and it also comes on when the engine coolant gets to 225*F. The ONLY reason that aux. fan should come on is if your in hot conditions where the primary fan comes on, but can't cool the coolant fast enough. Then the aux. fan will kick in and try to help cool the coolant before it goes back in the engine.

If you drive your car for about 10 minutes so the temperature is up to par, go back to your house and idle for about 5 minutes. You'll notice the temperature guage will start creeping. Once it gets past the middle a little going to the right, the primary cooling fan will kick on. Then you can watch the temperature guage start to creep to the left until it gets past the middle position. Then the primary fan will cut off.

If your in the mountains driving in 110* weather and the coolant temperature is real high, the primary fan will kick on. You continue driving up the mountain at speeds of 5-10mph and the engine is getting hotter from climbing the hill. Then the Aux. fan will kick in. That's one scenario. Very rarely will you ever see that aux. fan engage. It's only used if the engine is in danger of overheating.

[Headman]

Well there aren't any mountains here. Central Texas. I did however take the car for a spin up and down the highway and then let it sit in my driveway for half an hour. Yes the primary fan did come on when the temperature got to a little more than halfway on the gauge. Never have seen the aux. fan on yet. Must be a good sign.

[Retardo]

If you noticed after the primary fan kicked in, about 15 seconds after it running, you can actually watch the temperature guage go back to the left past the middle. Then in about 3 more minutes, the fan will kick on when the needle moves past the middle again.

Like I said, the aux. fan will only kick in if the engine is overheating, or if the primary fan can't cool the coolant fast enough.