Automotive Air Conditioning Information Forum

I have done a little ac work before so I am not a complete newbie but I am wanting info on where to start this project. I have had this truck for 10 years and very seldom drive it but I want to get the ac working. As of now, the ac is not working. The compressor does not engage. What is the first thing I should do to get this thing working again?

Kenny

Kenny, It sounds to me like the refrigerant leaked out--maybe not all of it, but enough that the system is now below the pressure threshold to where the compressor won't engage anymore. Either that, or the clutch gap is too wide.

The way I see it, given this truck's age, you have three options before getting into a much bigger and more expensive system overhaul:

One, try to locate the leak(s) via a "sniffer" and partial charge, repair the leak(s), replace the accumulator and orifice tube (OT), evacuate, and then recharge the system to the manufacturer's specifications.

Two, if you want to chance it and chalk-up the refrigerant loss to annual seasonal losses from the compressor shaft seal, recover the refrigerant (or have it done), replace the accumulator and OT, evacuate, and as above, recharge the system to the manufacturer's specifications (by weight, of course).

Three, reduce the clutch gap by removing a shim.

Two, if you want to chance it and chalk-up the refrigerant loss to annual seasonal losses from the compressor shaft seal, recover the refrigerant (or have it done), replace the accumulator and OT, evacuate, and as above, recharge the system to the manufacturer's specifications (by weight, of course).

Thanks for that quick response.

So, because of its age, you are saying that more than likely it is leaking from the compressor shaft seal? If I find that to be true, I will replace what needs to be replaced. The truck, even though it is old, is a great truck that has had a lot of work done to it.

If it's annual seasonal losses from the compressor shaft seal, you might be able to get away with just a recovery, evacuation, and recharge. I would still replace the accumulator (it has desiccant in it, a moisture absorbing substance), and OT.

Pay particular attention to the condition to the OT when pulling it out. If the screen is clean and oily, that's good. If it's clogged with "glitter" (metallic particles), plastic particulates, and black-ish gunk, that's not good.

In the latter case, you'd be looking at replacing the compressor with a brand-new component (not rebuilt), a new condenser, in addition to a new accumulator and OT. You should also solvent-flush the evaporator and lines/hoses (if not replacing them) to get out of the system every trace of foreign matter and contaminated oil. Then proceed to add the recommended amount and type of oil, evacuating, and recharging.

How much mileage has your truck logged?

It has 160,000 on the clock.

Given your truck's mileage—and presuming the compressor assembly is the original—I would replace it anyway. Many compressors don't last beyond 100,000 miles. There are some exceptions.

By replacing the compressor assembly, you will eliminate the clutch-gap question as well because it will come with a new, properly gapped clutch already installed.

You should be aware that compressor manufacturers typically require that the condenser be replaced at the same time, along with the accumulator and orifice tube, to maintain the factory warranty.

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My initial plan was to replace the complete ac system because of the age. I have a brother in law that can get all the parts at a super price. My only problem is the evaporator. That will be a real pita to replace.

I would flush it but I don’t know if my compressor is big enough to accomplish that

I was going to work on it a little today, but the air quality here is not very good and I’m doing the work outside.
Just out of curiosity, I think I’m going to put my gauge on it just to see where it’s at right now

kenlou wrote: Thu Jun 05, 2025 11:42 am My initial plan was to replace the complete ac system because of the age. I have a brother in law that can get all the parts at a super price. My only problem is the evaporator. That will be a real pita to replace. I would flush it but I don’t know if my compressor is big enough to accomplish that

Replacing everything is a good plan. But you're right...the evaporator is a real time-consuming nuisance to replace because some of the dash will have to come apart.

Alternatively, if you can get a look at the inside bottom of the plenum and the coil itself—perhaps using a borescope—you'll see whether they're relatively clean or gunked-up with vegetable matter and mold, which retain moisture and cause corrosion. In the latter case, the evaporator should probably be replaced.

If the plenum and coil are relatively clean, you can use a small pressurized cylinder to solvent-flush the evaporator. Even pancake-style compressors will be able to handle pressurization of the cylinder and subsequent blowing-out and drying the remaining solvent from the existing evaporator.

kenlou wrote: Thu Jun 05, 2025 11:46 am I was going to work on it a little today, but the air quality here is not very good and I’m doing the work outside. Just out of curiosity, I think I’m going to put my gauge on it just to see where it’s at right now

It's often difficult working outside.

Definitely use a proper Manifold Gauge Set (MGS) for testing both the high-side and low-side pressures. ACKits.com has an excellent, professional MGS in stock.

The single gauges—sometimes attached to a large can of refrigerant and sealer, which you never want to use—usually found in auto parts stores, home centers, and discount stores, won't get the job done because they typically test only the low side, and aren't very accurate at that.

My brother-in-law will sell me a complete kit for $350. That sounds pretty good to me.