a/c, non a/c cab difference

[Rob'68]

At some point before I bought my truck, a/c was added. It was originally a non-a/c. Holes were cut in the dash in the correct places for the vents. It's attached to the firewall with self-tapping screws. You can see where the original holes were. My question is this: What is the difference between a/c and non a/c firewall openings? I need to make sure everything works ok before the cold weather gets here. Thanks.

[Hutch]

Rob'68
Here is a pic of a 68 factory a/c cab firewall

[Hutch]

and here is a 68 non a/c cab firewall.

[Hutch]

Rob'68
There are a couple of other differences if you look at the first cab there is a hole in the firewall next to the chalk mark number 2on the left which allows a flap to be mounted inside the cowl area to open and close via a vacuum assisted module.
There is also another device that is vacuum operated which is attached to the passenger side cowl vent on the kick panel.
These have to do with the fresh air circulation.

Other will supply more detail, as this is a common upgrade
All in all if I were doing it I would look into aftermarket as they are much more efficient and the final cost is about the same

Have fun

[ddsmith]

All in all if I were doing it I would look into aftermarket as they are much more efficient and the final cost is about the same

This is interesting. I put in an Old Air unit in my truck and if I had to do it again I would replace everything except the evap/txv and maintain the normal control functionality. This is just my opinion. If you look at 69SixPackBee post you'll understand why. If going to R-134a, the POA can be adjusted to provide the proper setpoint. Anyone interested in further details can PM me and I'll explain further.