How to Re-Gas A/C From Scratch

[Quarterwave]

Hi everyone,

I've had a new A/C system plumbed into my truck, but the mechanic I'm using is giving me the run around, so I'm picking it up and will somehow make time to do it myself.

Aside from freon, what do I need to completely re-gas an A/C system in these trucks? Or am I better off just taking it to a dedicated AC shop?

I have new:

- A/C Compressor
- Condenser
- Freezer/Drier
- Evaporator
- Fan

I may need to replace a couple of hoses....

Thanks!

[Ford F834]

This link may help. I plan to do mine at home by renting the pump and gauges from autozone. The deposit is hefty, but you get it back. You can do it right and not have to pay a shop.

https://griffiths.com/ac-system-help-introduction/r134a-vs-r12/

[grumpin]

I have been doing my A/C on my rigs. Had to start from scratch if you will, as when I got my F250 the compressor and brackets were missing.

Since it's a 1986 it has the bigger tubed condenser and evaporator, at least from the research I did. I blew out the lines, condenser and evaporator with compressed air. I did not find a cleaner I liked (everyone in town had the expensive cleaner) so I poured isopropyl alcohol in everything and blew it out again.

Got a new compressor, accumulator and found the brackets at a local pick and pull.

I have an electric pump from Harbor Freight, also their gauges and I bought a valve to put on the service line (yellow), so I could control the pump and refrigerant better. And a valve for the cans.

After new o rings and tightening everything up I evacuated the system for an hour. Closed up the valves and let it sit for about 45 minutes to leak check it.

I used the small cans of R134 you can get easily. This is a good idea I got from someone, and that is to get a bucket of warm water, not hot, to put the cans in while you are servicing.

With vacuum on the system still, I hook up the can to the service line, open the proper valves and let the pressure from the can and the vacuum pull in as much refrigerant as possible. On this big of a system you will have to jumper the low pressure switch to get the compressor clutch to engage.

Start the truck, turn on the A/C and keep the can in the warm water till it's empty, with my valve I can close it to change cans.

When the system is completely empty I like to determine how many pounds it holds and aim for that much refrigerant while monitoring the gauges for the correct pressure for the current outside temperature.

Hope this makes sense and helps.

[85lebaront2]

I have been doing my own A/C work for years, I actually have an R12 license. One item you may want to consider changing is the orifice tube at the evaporator inlet, they come in different sizes and it helps to increase it one size from the original.

I converted Darth to R134a years ago and it cooled very well with the FS-6 compressor and original condensor. I have since then changed all the system to 1994 up components, partially because I had to change the compressor when I converted to the EFI components and polygroove belts. I bought a new 1994 up condensor and found a set of hoses at the local Pick-n-Pull (460 stuff can be a royal PITA to find) since Darth is a crew cab, I used the red orifice tube and a new 1994 up accumulator.

Biggest thing on charging it, first a good vacuum, 30 mins minimum once it gets all the way down, but before you close everything up, you need the proper quantity of PAE refrigerant oil, PAG is the normal oil for a factory R134a system, but, if there is any chance that some trace of the old R12 oil being in the system, you don't want to mix them, you will end up with a mess.

On quantity of R134a vs R12, the rule says 80%, I have found that is a bit low, you really need to go by temperature, at 80% you will find it does not cool adequately. On the accumulator, the low pressure cutout switch, the one you need to jumper during the initial charging, there is a screw between the terminals, this needs to be backed out slightly, using the low side gauge, set it for 34° degrees, the reason for this, R12 and R134a have different temperature/pressure curves, below 60° the R134a curve has lower pressures for the same temperature, about 60° the pressures are higher.

FWIW, the local shop here does A/C and alignments, last year I had to replace my right inner tie rod ($$$$) before inspection, I had him do the replacement and toe adjustment, his comment after pulling Darth on the rack was, damn A/C is freezing. Properly done, you will be very happy with the result.

Good luck with it!

[grumpin]

Orifice tube! Yes I forgot that. Good point LeBaron!

[Steve83]

I'm ASE & MACS certified, and I quit doing that kind of work on my trucks many years ago.  I found it to be VASTLY easier, quicker, cheaper, & more-reliable to just swap the whole system out for a junkyard '94-97 system (I find them all the time) from a truck with the same engine.  Lift it out, set it in, and drive.  No messing with conversion, or flushing, or chasing leaks.  And everything works the way it was designed to, so it blows just as cold as a new truck does.



Follow the links in that caption for the details, but it's really pretty simple.

[Gary Lewis]

Interesting approach!  I'd never thought of that.  Cool!  

[Steve83]

The only limitation is that the compressor is set up for serpentine belt.  That hasn't been a consideration for me for decades, so it commonly slips my mind.  But I just realized I need to remember it more often on this forum...

[Gary Lewis]

Good point.  I am going serpentine on Big Blue, but not on Dad's truck as there aren't any factory brackets for a 400.

[Steve83]

I assumed it would use the same parts as a 7.5L (460), but I'm not nearly as familiar with big blocks or V8s in general.

[Gary Lewis]

Unfortunately, the M-Block and Clevelands use different brackets for everything.  Different than Windsor or 385 Series.  So no factory serp brackets, and I can't figure out how to easily mod others to fit.