Ducting and Switch/knob question

[Gary Lewis]

Thanks for that info, but here is the interesting thing then, I have the 18490 defrost portion you show in the picture you posted....but my vents are very specifically the ones I circled in the other picture showing the AC truck (the two piece tubular ones). So my guess would be someone was swapping in an AC and never got it finished, or was in progress of acquiring parts, etc. I do not have that 18471 style from the heat only truck. I suppose this can also be confirmed because the dashboard in my truck has vents, where the heat only truck did not....so I would assume someone started an AC conversion, gathered some pieces and it fell through the cracks or they discovered the firewall difference and went all stop with it.

So you have a truck with a heater firewall and HVAC/Hi-Lo Vent ductwork. Given that, I don't think anything is going to fit right. I don't know this, but it makes sense that it wouldn't work - at least to me.

One approach is to acquire the right heater ductwork and use it, with nothing connected to your dash vents.

Another is to modify the firewall to accept the A/C underhood box.

A third is to see if you can connect the heater box with the A/C ductwork.

But if you want to have A/C, then you either need to modify the firewall or use aftermarket A/C.

[jstone4646]

So you have a truck with a heater firewall and HVAC/Hi-Lo Vent ductwork. Given that, I don't think anything is going to fit right. I don't know this, but it makes sense that it wouldn't work - at least to me.

One approach is to acquire the right heater ductwork and use it, with nothing connected to your dash vents.

Another is to modify the firewall to accept the A/C underhood box.

A third is to see if you can connect the heater box with the A/C ductwork.

But if you want to have A/C, then you either need to modify the firewall or use aftermarket A/C.

Well I do have the 85 which has a full interior, ducting, engine side also, all hardware and necessary electronics....and it all works. She is a dual tank truck but I can just leave that switch electrically disconnected...or just put the dual tanks in the 84.....options, options. The firewall on the 84 would need to be cut and modified but I can work that out.