fan switch or fan motor?

'92 Dodge Ram Van B250 with intermitant blower. With the fan switch on in any position, the blower will cycle on and off.

2 things I noticed:
1 - some amount of "squeal" from the vent when the fan is running
2 - it seems like the fan runs less when I accelerate or when at higher speeds (70 to 80 mph)

My gut feel is that it's the motor but if there were a simple way to test the switch, that might be easier and less expensive if it in fact were the switch.

thanks in advance

You could disconnect the two wires going to the fan and connect them to a voltmeter. Turn the ignition on and watch the meter for fluctuations as you cycle through the fans speeds. If it fluctuates it's the switch, speed resistor, or a problem within the wiring.

If that is inconclusive then you could connect two wires from another power source within the vehicle (the fan will only run on high) and see if the fan runs intermittently. If it does, then you have a bad fan motor. Considering the squeal I'd lay odds that it's the fan motor.

Thanks, easy enough. I'll give it a try.

The blower switch started acting up on mine. It was because the switch was getting hot with the blower on high. It eventually deteriorated the switch. I replaced the blower motor and the switch and it was fine.

Blaze