I don’t know much about HVAC units, but I just went through this early this season. Just feel the lines that go in and out of the outside unit. The insulated line should be cool, might be sweating, and the line from the compressor to the coil should be pretty hot, but then cooler when it leaves the unit and goes back into the house. If the return line is sweating, you are getting some cooling, just not enough. If they’re all about the same temperature, the compressor probably is not compressing even if it’s running.
I don’t know if you’ve heard of the “arctic air R22a“. It’s propane, and you can use it to top off the house system or your car system. Propane is much more efficient than the Freon, but of course it’s flammable, so you might not want to have the whole system full of it. I’ve used it many times. I bought this kit when I tuned up my home system earlier this season.
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I put one can in one system (I have two systems, up and down). All pressures came out OK, and knock on wood, they’ve been working perfect all summer. I didn’t mind buying the three cans with the little adapter, because I always have to top off the F250 and one of the Lincoln’s a little bit.
I also recently bought a cheap gauge set with the adapters so I can hook it up to the house as well as the car. It was only $35. I’m sure you saw my post when I fixed the AC on the Road Ranger, and the 35 bucks was some of the best money I spent in a year.
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Regardless, if you don’t know your HVAC guy really well, beware a common rip off with the service companies. They’ll tell you the service call is only $50, but if they have to add any Freon to the system, it’s $150 a pound or something like that. And then they tell you that you needed 9 pounds.
You want to have a look at the gauges the second they hook them up, and ask them how they’re going to measure the amount of freon they use if they have to add any. The most common ethical way is they have a little bathroom type scale with them, and they weigh the can before, and they weigh the can after.
If your system is already cooling at all, it should need more than a pound. If your gauges are really close to the optimum pressure, you could also estimate the amount of free on they’ll need. If they’re 10% off, maybe it’s a pound. There’s a label on the side of the AC unit outside, and the number of pounds they used in your system in your house should be marked on that label. It’s all pre-printed except for that number.
One of the little cans is 12 ounces for reference..
As always, I hope it helps