Heater intermittent

OK, it's now winter and I've been blowing off (no pun intended) this irritating problem for a while now, but can no longer do so as I have no dependant defroster anymore.

My truck's air blower has a mind of its own, it works when it wants to. The outside temp doesn't seem to matter, some days it works, others; it doesn't. I've already pulled apart the dash switch and it seems fine,; all contacts are connected and lubed accordingly. Evidently the problem lies elswhere. When it works, all functions of the blower/heater system work fine. The vacuum system is fine as well. Any advice out there? Thanks, Lee

For the fan blower being intermittent it's either the blower motor itself, or it's the inline resistor.

Yeah, I figured it was an electrical glitch but thought I'd find out more about it before tearing the dash apart. Where is the resister located? Any tips for getting to the blower? I've torn out heater cores before on Japanese cars, but not on one of these.

Today as I was driving home in 30 degree weather, the heater suddenly came on; now that was a nice surprise as I was freezing my arse off. Any help in isolating this problem would be appreciated, Lee

For the fan blower being intermittent it's either the blower motor itself, or it's the inline resistor.