88-94 HVAC control swap possible?

[chevy751]

I have a 88 with the old style climate control and no max or circulate button and I’m trying to run a billet piece over this.
All the billet pieces I’m finding and have are for the newer style with the max and recirculate and I’m wondering how I can make this work and be correct? Is it as simple as a plug and play or is there something more to it since I don’t have those two buttons on my original control.

Picture of one installed is the older style that’s for the truck, and the one not installed is what I’m trying to run.

 

[DerekTheGreat]

The A/C recirc button debuted in 1991, I think. Even though the wiring harness is the same and it'll turn on and function if swapped, it won't work for very long. Main reason is there is a brain inside controller and it is expecting a certain voltage feedback from the stepper motors. I can't remember correctly off the top of my head, but I think the early stuff (1990 and down) operate on 8 volts and the later stuff (1991 and up) operate off of 5 volts. So at best what you'll end up with is a head unit which works fine for a day or so and then the display will start flashing and you'll lose control of your HVAC system. Ask me how I know

My idea was to swap resisters in place so that the head unit saw the voltage it expected, but I never got around to doing that.

 

[Dropped88]

It'll work you have to change the control head, harness, and recirculate actuator.

It's not a bad job and you can do it with the dash in. But if you go with a 94 setup you'll have to cut the hole out bigger for the blower resistor but you gain 4 speeds.