The Stovebolt Site Forums The Shop Area The HiPo Shop Initial charge of A/C

I'm putting A/C in my truck and it is now ready for charging. I have no experience at this so am looking for feedback on the initial charging of the system. Is this a DYI task or best to have a shop do this? I know the parts stores sell small amounts to top one off if it has leaked some but haven't heard about the full initial charge. Thanks for any ideas here.

Dennis

The volume of refrigerant isn't so much a problem but the evacuation of the system is. To do it properly the system needs to be put into a vacuum to remove air and moisture before it is charged. So if you haven't got access to a refrigeration service vacuum pump you'd be better off taking it some place to have it done.

After your professional charges the system insist he/she checks for leaks. R134 is not cheap and you don't want to have to do it over. After the initial vacuum and charge you can in a year or two, if needed, use the DIY kit and top it off.🛠

Thanks for the advice guys. That's what I'll do then.

Dennis

I would talk with the manufacturer of the system to get some idea of the pressures or fill amount. I helped a local fellow with an Old Air a/c system in a '55 Chevrolet car since I have the equipment at work. We never could get very cold out of it, and the pressures were really off from everything else I have worked on. He called Old Air later and they confirmed the pressures. Total fill amount was hardly nothing. A local shop would benefit from the information.

Joe

Each installation will have its own "complete fill" specifications, depending on the length of the hoses, size of the evaporator and condenser, any receiver/dryer parts or other pieces unique to your system, etc. On a custom installation a pro is going to eyeball the parts layout, evacuate the system with a vacuum pump for several hours, install a slightly low charge by his educated guess, and add a little at a time until the pressures look right. It's definitely not a job for a rookie. You'll also need the proper type and quantity of lubricating oil to keep the compressor from seizing up, and that circulates with the refrigerant and also affects the total quantity of refrigerant needed.

At least that's the way I've been doing it since I started helping install add-on air conditioners at Dad's shop in 1961.
Jerry

Most of the older units & add on units have a sight glass. The Tech can put in refrigerant until the sight glass clears & just a little more.

I'll check with Vintage Air before I take it in. I haven't had a chance to choose a place to take it yet. On the site glass, I have one on the top of the dryer and I have it so it is easy to see. Thanks.

Dennis

"Is this a DYI task or best to have a shop do this?"

Dennis,

I've put AC on 3 vehicles that didn't originally have it with no prior AC experience and found it to be totally doable. It does require a vacuum pump and a gauge set, both readily available. The procedure is simple and is explained in service manuals. There are probably countless amateur videos online as well.

The vacuum pump's function is simple. It creates a 29+/- inch of mercury vacuum in the system and at that vacuum water in the system boils at about 70 degrees F and is sucked out as a vapor. After vacuuming for a while the vacuum pump is turned off and the gauge set is monitored to see if the vacuum is maintained or if there is a leak.

If there's no leak refrigerant is put into the system to the correct amount or until the sight glass shows no more bubbles. And then you're done! Not much to it.

If the system does not have a sight glass. Temperature pressure charts are used, know the condenser temperature and evaporator temperature while ethe system is running, chart tells you the expected pressures. Fill until the pressures are correct.

If you are using 134 and fill till the bubbles disappear IT'S WAY OVERCHARGED. Use gauges and go by the readings for the temperature at the time you are charging.