Help with small vacuum hose that enters cabin

[Scoutboy74]

Subject vehicle is a '72 1210 4x4 t-ette that has been placed in my temporary care by the owner. Its a factory ac version with blower ducts in the dash front. One of the final items to resolve is the small diameter vac line that runs from a vacuum reservoir on the engine side of the firewall, through the firewall and up behind the dash somewhere. I assume it is part of the cabin hvac controls. The rubber hose appears to be oem and is very rotten. The entire length needs to be replaced. I'm assuming that I'll need to pull the dash pad and the instrument face plate off to gain access. The radio is already out, so that's a plus. I'm hoping that I will be able to see and access the termination point of this line through the radio cavity. Just putting this out in case anyone else has been down this road before and has some sage words of advice for me. Tia and merry Christmas!

 

[FDChappie]

I would guess that it goes into the hvac controls as you've said. Hopefully there is still a stub of hose there and not just an obscure nipple hidden behind some levers. Hopefully my '71 t-ette will be 4x4 some day.

 

[Scoutboy74]

Yeah chappie, the entire hose is still intact for now. The engine side end is split and all of it that I can see is badly checked. Just a vacuum leak waiting to happen, if it wasn't leaking already. I'm thinking that hose might only be used for the ac system and not for heat or defrost. If I can confirm that, I might hold off on replacing it for awhile, since the ac system is non-op at present, plus its daggum winter time! I have the fitting on the reservoir engine side capped so vacuum can't escape. I'll let the owner make the call as to whether he wants the line replaced now or later. He's getting anxious to have the truck back. Thanks.

 

[FDChappie]

On my non-ac truck all vents are cable operated. I've taken apart an ac unit a long time ago and iirc there are some diaphragms used for the vents.

 

[Scoutboy74]

A poster to my thread over on the bp informed me that this vacuum line is involved in some of the heater control, so that settles it. I'm going to have to chase it down. He said that I should be able to see it connected to the back of the hvac control panel through the radio hole.