No high speed fan

[kgouldsk]

My high speed fan won't come on when my temp comes up. I run at well over 200 degrees after a few runs. I pulled off the high speed fan relay, energized it, and the contacts all close properly.

I BELIEVE can can short the coolant temp sensor to ground to signal the high speed fan to kick on - can anyone confirm this? If it doesn't, where else should I look? Is there a specific fuse for high speed fan, and if so, where is it?

Kevin

 

[buickboy]

Kevin-
Yes, short the fan temp switch to ground with a piece of wire, and the HS leg of the fan should be on. If it comes on then I would think the switch is bad, ECM is not driving the temp switch to ground and/or would look at the wiring back to the ECM or the ECM.
Mitch

 

[Turbo Brian]

The high and low speed fan relays are the same part #, so you can swap them to check whether the relays are working or not.

 

[scottyb]

The high speed fan switch is on the top of the intake just below the throttle body/cables. It's a single wire. Pop it off and ground the wire with the ignition on. Be gentle as the connector is likely old and brittle. I believe the high speed switch is ~210 degrees. The ECM does not control high speed, only this switch OR the AC pressure switch. The fan must run high when AC is operating.