Heat defuser

[rpearson63]

I am in the process of repairing all the vacuum doors on my grandfather's 78 gmc. I need to get to the vacuum pump on the back side of the defuser.  I have located the top 2 bolts that hold the defuser box in but cannot find the bottom 2 bolts . It almost looks like I have to remove the inner fender to locate them. Is this the case? Im doing a partial restoration on his truck. Making the inside of the cab up to date. Getting everything working properly. But keeping the exterior with that older rustic look. It's coming along nicely.  Any help would be greatly appreciated

[Rapid Roy]

Welcome

[Henry]

Hi R:
I assume you are trying to remove the heat distributor assembly that is on the inside of the firewall at the pass side hidden by the dash...? Yes, this assembly has one or two studs low down that go through the firewall to the engine side, and then there are nuts on the studs on the engine side of the firewall. One is hard to see...you can feel down there with your hand under the blower housing on the engine side to locate it. The lowest nut is a bear to get at and it is easiest by loosening the pass side fender skirt and moving it forward and down a bit to get some clearance. There was a post about 6 months ago on the HVAC board (a child board to interior, I believe) where we discussed this with a guy trying to remove the heat distributor to replace the heater core.
Regards,
Henry