ok you talked me in to doing it the right way. i'll let you know how it goes.

 

I am going under the dash after the blower motor on my 76. So far I have found the seal where the freon lines enter/exit the evaporator housing needs a replacement. Any idea who has one? Searched NPD and LMC - no joy.

 

Well, I got it done. Here are some tips - no particular order -

the factory book says to unbolt the dash where the RH end of the dash meets the cab inner wall. Good idea - it gave me a little more clearance to reach behind the evaporator and extract the heater core and the blower motor/squirrel cage. Also, the book says to undo the dash bolt under the dash just to the right of the glove box - I did that, too. You would be amazed what getting another 1/2" of gap between the evaporator and the box it came out of will do for your day!

I bought a 5/16" magnetized nut runner bit to use as a screw starter. Many of the self-tapping screws just fall out of your driver at the darndest times - with this job, gravity sucks. The magnetized tip held the screw just long enough for me to get the hardware started.

If you swap out the heater core and decide not to plumb it up for the summer, fill it with 50/50 and cap it anyway. the cold air being dragged across an empty core might cause humid air within the core to sweat, and there goes the core due to internal corrosion. I am SE of Houston halfway between Houston and Galveston, and all of the world's humidity comes here to die.

There is a plastic seal that is supposed to snap over the two freon lines to seal the conditioned air from leaking out of the engine bay-side air box. There is also a second seal in the same area that is held in place by a stamped steel cover and two screws. Neither of these seals appear to be available, so if yours is/are petrified, throw it/them far away and get some UL-listed (better quality) aluminum duct tape and make your own seals. Lots of little pieces of the tape will do the trick. If you want to add insulation to the surface of the tape so it does not sweat, get some double-sided adesive foam tape and cover the aluminum tape with foam tape. Then, cover the foam with aluminum tape again. For a stock look after all this taping, you can dust the tape with flat black aerosol paint, but I was just happy to get through with this blood-letting experience not to care what it looked like!

The BLEND DOOR - what is it? It is the last thing to remove before you get to the blower motor. If you are tired and have little patience at this point, or your body feels like you have been thrashed with a stick, remove the blend door the next day. The blend door has three pairs of little steel fingers on the side of the door that faces the blower motor. Each pair of these fingers are shaped so they will snap on to either the steel wire shaft that goes up through the top of the air box to a cable which rotates the wire, or to the OTHER steel wire shaft that is closest to you that is there only to allow the door to translate - that is, the blend door does not swing like it is on a hinge, it moves fore and aft like it might be a sliding patio door. EACH OF THESE WIRE SHAFTS look like a speeder wrench. To get the blend door off of these two shafts, you have to insert your hand on the side of the door closest to the blower motor and PRESS the door to the right side of the truck, which will cause the door to snap off of the wire shafts. NOTE - If you decide it ain't worth the trouble to put the blend door back in the truck, your temp lever on the dash will give you the same temp no matter what you set it at. That is because the temp lever drives the blend door position!

By the way, I trashed my carboard glove box interior getting it out through the glove box opening in the dash. Thinking back now, if there is clearance to allow the cardboard glove box to slide forward and down to the cab floor, you get to use it again instead of ordering another one from NPDLink or LMC!

Good luck!