My heater leaks hot air inside the cab so I put a common shut off valve on the heater hose inside the engine compartment area.

Is it a pain to take apart the heater box cluster to find the shut off valve? I changed the mini radiator core to the heater once and that was sort of a pain. Is the shut off valve more involved than that? I have never done one. Does the whole box have to come down?

 

I personally never noticed a shut off valve in my 66, though I have seen them in other vehicles and know that they really are not that labor intensive. I would make sure that your truck is cold and that there is no pressure in the coolant system at the time. You never know when you may need to drain some coolant to make it easier though. It won't be that hard to change honestly if you need to.

 

Look under the hood on the right (passenger) side inner fender apron at the inlet to heater core heater hose.

Depending on which heater your truck has, spliced into this hose is either a cable operated heater water valve (C3UZ-18495-A) or a manually operated heater water shut-off valve (C5TZ-18495-A).

1965/66: There are two different types of Fresh Air heaters.

The Deluxe heater has the blower/temp control switch/cable mounted into the dash (below the cluster), and two additional cables mounted to a bracket, that bolts under the dash to the right of the steering column.

One cable opens/closes the heater water valve, t'other operates the damper door that allows fresh air to flow into the heater box.

The Economy heater only has the blower/temp control switch/cable (same location). So, to turn on/off the water that flows to the core, the hood must be raised and the valve manually operated.