Airconditioning ?
 

My factory air (72/402) blows cold until the engine heats up and then hot air becomes mixed with the cold. Sometimes hot air blows out of the vents when the fan is off and sometimes the blower stops when I am idling and starts again as soon as I accelerate. Could this be the diverter? Has anyone experienced a similar problem?

Do the levers on your control unit still move smoothly? Sounds like some of the cables are broke. Possibly, not too good at trouble shooting A/C yet, haven't finished mine yet.

There is a vacuum operated heater shut off valve on your passenger side inner fender that is supposed to shut off when the heater is off. It doesnt work, apparently, similarly to mine, which does work, when it wants too. I would say the blower coming on and off is more of a loose connection, but perhaps it is related to system voltage, on an old truck, at idle, the alternator may not produce enough juice to run things at full capacity, but when you accelerate, it does. Confirm this tonight, with the headlights, if they dim at idle, then brighten when you give it gas, that is it.

Thanks to both of you...I will check it out when I get home.

I installed a manual shutoff valve along with a new vacuum operated one to insure that the hot water was shut off to the heater.
It was just an extra precaution to keep the hot water out of the core.
The electrical connections on the fan switch run alot of amps and will overheat and melt the plug on the back of the fan switch, which could cause the fan to lag at low speeds.

Just some things to check
Have fun and good luck

TAKE A SUNDAY AFTERNOON!!
 

I had a broken AC lever and thought Id just replace the heater control. After tearing into it , I found that all the cables and doors in the ducts were "dry". Thats what broke the lever in the 1st place. I ended up taking the ductwork under the dash apart, along with the cables, and lubricated everything. When putting it back together, I adjusted all the doors to make sure they werent letting in outside (hot) air. MAN , what a diff. that made . Works like a new truck. PAIN in the @ss- but worth it!