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Topping Up Truck AC

Started by lxskllr, May 29, 2019, 05:42:58 PM

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lxskllr

Bought some refrigerant a couple years ago; mainly for the pressure gauge so I could check out a problem, but I didn't need any juice at that time. AC hasn't been working great, so I checked it today, and it was low. It was a real struggle getting anything in the system. The hose wouldn't simply click in place. It all was a dying strain keeping it pressed in place while I checked the pressure, and tried to add refrigerant. I didn't get it where I wanted, but it's blowing colder, so I'm calling it a win for now.

Anyone else have issues like that? Bad hose maybe? It's the first time I've filled AC. Looked like a straightforward job, but it was a real hassle getting it in, and I lost some in the process.

alan gage

I do automotive AC for a living and have never understood how people are supposed to get a proper charge with those kits they sell. That's not to say it can't be done but I've only ever seen them with a gauge on the low side and you need to see both high and low side pressures (and understand what they mean) to do a proper top off. You'd be better off walking around the system with your hands feeling the line temps on both high and low side but, again, you need to know what normal feels like.

And if the system is empty it needs to be evacuated with a vacuum pump to remove the air and moisture. Otherwise air contamination will have the system pressures running too high. We see this quite often when people use these kits to fill an empty system.

Even with experience I often don't trust myself to "top off" systems anymore. Most of them have such low capacity that being off only a few ounces can cause performance problems and it can be hard to judge by pressure/feel when the system is "full" because the gauge readings and temps will feel different depending on ambient temperature. It's easy to over or under fill a vehicle at 50 degree ambient temp and then have the pressures running too high or low when it hits 95.

Alan
Timberking B-16, a few chainsaws from small to large, and a Bobcat 873 Skidloader.

Tom King

I have used those kits in the past too.

I have one tractor that too large for any of my trailers, and it would cost more to get it hauled somewhere than I could buy the proper equipment for.  So, long story short, I bought all the stuff ( good vacuum pumps go cheap on CL these days since most pros are now using automatic rigs), and learned how to work on them myself.

I'm sure I'm nothing like as good as Alan, but it's not too hard to learn how to understand the process.

Since learning what it takes to properly fix an AC system, I'm really surprised those little kits with a can of refrigerant, short hose, and gauge, are even legal to sell these days.

alan gage

Quote from: Tom King on May 29, 2019, 07:35:19 PMI'm sure I'm nothing like as good as Alan, but it's not too hard to learn how to understand the process.


Like many things it's pretty simple 90% of the time. And if you're only working on your own stuff there's a good chance you'll never run into that other 10%.

Alan
Timberking B-16, a few chainsaws from small to large, and a Bobcat 873 Skidloader.

Tom King

And without keeping parts on hand, there is no customer to complain about it sitting in the shop until what I need next gets here.

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