[70rs/ss]

Originally Posted by Rdub

I might be wrong but, I think repalcing the heater core on an AC truck is a different process than non-AC..... I asked this same question a few weeks ago with few responses and vastly different opinions (couple people said they thought it was same process as a non-AC truck and another person who had recently done it described replacing it from inside the cab)... so, bought a gmc shop manual..... haven't had time to look at it but will tonight and get back to you.... there is a great thread on heater core replacement for a non AC truck in the faq section but, at this point I'm not sure how much of it would apply to an AC truck. Also tried the search function and it's apparent it only searches on threads placed since the format change a few weeks back. If indeed it's a different process, I think a good candidate for a faq write up with photos, which I plan to do, unless you beat me to it.

I think you are correct as the condensor or evaporater (whatever that thing is called) is housed in the firewall box in the location of the heater core on a non AC truck. My vote now is that the heater core will be replaced by removing the under dash unit from the inside of the cab on the passenger's side. Way longer and a lot of cussing will be required, just avoid using the hammer! Good luck.