I have a 1998 Volvo S90. I usually have to charge the a/c once a year to keep it cold. Today while driving the a/c went from cold to hot almost instantly. I turned it off, waited a minute and turned it back on. Cold just like normal. Two minutes later, hot air again. Turned it off again, waited a few minutes, turned it on, cold air but only for about 30 seconds. This was all done while driving. Any suggestions on what might be causing this?
I’d take a look at the vacuum connections from the engine to the dash controls. Providing, of course, that it is a vacuum controlled system.
You shouldn’t have to recharge it every year. It means there’s a leak, which should be found and fixed. Until you do that everything else is a waste of time and money.
Since I have neither the specialized equipment nor the expertise for automotive AC work, whenever I have a problem with the AC in my vehicles I take them to a shop with the necessary equipment and expertise.
I suggest you do the same.