Air Conditioning Swap

[Preston Tucker]

Hello everybody!
I have a 1974 GMC k20 project truck and recently picked up a rolled 1987 c10 with an air conditioning unit, so long story short. I want to do an ac swap! I have all the stuff for it but if anybody has gone about a swap like this before that would be helpful for you to drop some pro tips here.
The cab is off both trucks and I know i have to move the heater box hole in the firewall but i dont know what else.

Feedback would be super helpful!!

 

[SquareRoot]

How's your fabrication skills? It can't be that hard. It has to be less work than the Vintage Air system I put in my 85.

 

[Matt69olds]

I would think fabricating a new firewall opening, and swapping all the ductwork would be the majority of the labor. If your handy with a welder and comfortable with sheet metal work I’m guessing it wouldn’t a huge project

 

[Preston Tucker]

How's your fabrication skills? It can't be that hard. It has to be less work than the Vintage Air system I put in my 85.

My fabrication skills are ok, I am an amateur and only 18 but ahead of the curve for my age. i was just going to try and cut ac part of the firewall out of the 87 cab and install it in mine.

 

[Preston Tucker]

I would think fabricating a new firewall opening, and swapping all the ductwork would be the majority of the labor. If your handy with a welder and comfortable with sheet metal work I’m guessing it wouldn’t a huge project

I know i can do that part of it, the part that worries me is the electrical part of it since i do not have much experience in that field.

 

[Scott91370]

i was just going to try and cut ac part of the firewall out of the 87 cab and install it in mine.

I'm far from any kind of fabricator but this is what I would do as well. Measure many times, cut once.

Oh yea, and post pics of the process/prgress!

 

[Markmx6]

The electrical isn't that bad. Just trace your harness' for power and ground. Wiring can be really simple, you just have to break the sections down into smaller pieces in your mind.

 

[Bextreme04]

The AC harness electrical is beyond simple on these old trucks. Most of the heavy lifting is done by a vacuum system that is selected by the HVAC controls in the dash. The hardest part is going to be rebuilding all of that vacuum stuff and restoring the A/C box before you install it into the 74. Its not going to be in good condition, they never are, and you definitely don't want to spend all this time doing the swap just to put bad parts in and chase your tail troubleshooting why it doesn't work. There are lots of threads on here of people rebuilding their AC units, start reading to get a good idea of what to expect and then just jump in and do it!

 

[Matt69olds]

The electrical part of the A/C system is a separate harness. Unhook the original, plug in the new