A/C retrofit on a 90 3500

[PumpMan]

Hi guys,

Has anyone seen a write-up on retrofiting a complete A/C system into a non-A/C 88-90 truck? The mechanical system is easy, I'm just not sure what the easiest way is to hook up the controller.

I would definitely swap out the entire HVAC system under the dash and all the accessory pulleys (easy with a junkyard donor or two)

This truck has a pump hoist mounted in the bed, and swapping trucks isn't an option. I don't want a roof unit either, 255 A/C might have to do, but I would like to know if there is a write-up somewhere. I will have some time on my hands this winter and this looks like a fun project.



Thanks!

 

[upper_tanker]

I probably don't understand your question.... but if you can find a donor truck or two that still has the entire a/c system, why not take every component that you need, including the radio/hvac controls?

 

[someotherguy]

*and the dash harness

Richard

 

[Schurkey]

The older cars used different body stampings at the cowl for A/C vs. Non-A/C. Is that true of these trucks?

 

[someotherguy]

To a small degree. My only experience with a non-A/C GMT400 was a later model, ex-phone company utility truck - a 99 or maybe 00 3500. It was lacking a few holes in the firewall but overall not that different. Had a customer wanted me to add factory A/C to his truck and I was game, had all the parts needed, but the total came out to more than he wanted to spend on an old work truck. (and TBH I thought I had quoted him a little low...) I do regret not having had the opportunity to perform the job as it was interesting to say the least. How AT&T got away with giving crews in Texas work trucks with no A/C ..... I have no idea.

Anyway with all that said, the later GMT400's without A/C could be different from OP's 90 as well, since the firewall did change a bit over the years; 88-90 was one design, 91-94 another, 95 might be a one year (minor differences), 96-up changed yet again, etc. and so on.

For a related example (sheetmetal differences based on original equipment), depending on year, some trucks that came without power windows/locks did not have the holes in the cab's A pillar for the wiring harness pass-through and related boots.

Richard

 

[PumpMan]

Thanks! This truck was originally a cherry picker for either a power or telephone company, must have been common practice. I'm going to be spending most of my next few summers in this thing, so A/C is critical!

looked at it more seriously today and it doesn't look too hard, Original Air makes a kit with R-134A optimized orifice tube, compressor, evaporator, received and condenser. There is an idler pulley bolted where there compressor should be and the air box under the dash is identical, except for a recirc door. It's going to need a few extra holes in the fire wall, but I have hole saws. I'm looking forward to this job, will post photos once it's in.

 

[PumpMan]

Thanks! This truck was originally a cherry picker for either a power or telephone company, must have been common practice. I'm going to be spending most of my next few summers in this thing, so A/C is critical!

looked at it more seriously today and it doesn't look too hard, Original Air makes a kit with R-134A optimized orifice tube, compressor, evaporator, received and condenser. There is an idler pulley bolted where there compressor should be and the air box under the dash is identical, except for a recirc door. It's going to need a few extra holes in the fire wall, but I have hole saws. I'm looking forward to this job, will post photos once it's in.

 

[someotherguy]

While you have the donor truck there make a good template for the holes. You don't have much margin for error on the evap and condenser lines; if they get too close to the sheetmetal they're going to get sawed through over time.

TBH you don't need all those new parts if you have good ones from a donor truck. I mean you'd do well to have a new compressor, condenser, orifice tube, dryer, and especially the rubber hoses...that's the same list I'd replace from an already A/C-equipped truck that had a compressor failure. However, the evaporator and other parts from the donor should be 100% fine.

Do yourself a favor and get the whole under dash box from the donor truck. It'll have all the needed doors, electric actuators, etc. but take it apart and clean it and the evaporator core fins out thoroughly. You'll find tons of trash in there.

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I wrapped the connections up and dunked the core into a bucket of diluted A/C cleaner.

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Richard