77 Ford blower motor probs

Hey all,

I have an old 77 Ford F150. I've had it for about two years, and this is the first winter that I've driven it in.

My problem is with the heater / blower motor function. 50% of the time it will not turn / run. The other 50%, it will run as it's supposed to. I often have to wiggle / tap on the fan speed switch to get it to turn, (which only works once in a while).

I noticed that sometimes, if I turn the ignition off, and re-start the truck, that the fan will occasionally start turning, and runs as it should.

The battery cable ends are clean, and there is good clean connection at the ground cables and the smaller ground straps that run from the body to the frame / battery.

So with this info, where should I start to trouble shoot this ?? My first thought was to replace the fan switch, until I discovered that turning the ignition off and on again sometimes has an affect.

I am not very knowledgeable when it comes to electrical problems, so any ideas will be appreciated !!

Also, if it makes a diff, it does have factory air.

Thanks,

Ron

My first take would be that the fan blower motor brushes are worn out and barely making contact with the commutator. The fact that you can make it blow by tapping on the speed switch and that they were a common problem back in those years thats where I would look first. Remove the A/C-Heater control panel and inspect the wiring to the fan speed switch. You'll probably find the wiring burned and the plug half melted. You can replace just the switch. You dont have to buy the whole panel. But you will have to cut back on the wiring and crimp new terminals on them. Dont be surprised if the blower motor is worn out also,(thump the motor with your fist and see if it turns), but check the switch wiring first.

Thanks DeltaP, for taking the time to reply to my post. I will do as suggested and go from there.