Dear Car Talk:

We have a 2010 Volkswagen Jetta. The air conditioner takes at least 15 minutes to get to a cool temperature. Until then it blows plain old hot air. Once it does get cool, it will stay cool for a good length of time. But then it will get less cool for a while and then go back to cool again. Also, it seems that it starts to cool once the engine temperature reaches 190 degrees.

We have been to the VW dealer, and they have not been able to fix the issue. They have now said, at this point, we need a whole new air conditioning unit. We hate to spend $1,500 for a new unit when there could be another solution to this problem. My husband and I are so confused. Is there another solution? Love your column ... read it every week! Thanks. -- Cynthia



There's always another solution, Cynthia. There's rolling down the windows, or putting a five pound bag of ice on your lap.

It sounds like you may very well need a compressor, Cynthia. That's the $1,500 solution. I assume they've verified that the refrigerant level is fine, or even recharged it for you.

But there's a small chance you just need something called a high pressure switch. If the pressure of the refrigerant inside the compressor is too high, the high pressure switch will cut power to the compressor clutch, so the compressor doesn't blow itself up. And while the compressor clutch is deactivated, you'll get hot air. So maybe that switch has gone haywire?

Normally, a scan will pick that up. But if the switch wasn't misbehaving when your dealer had the car, he could have missed it. And the dealer may not have wanted to put in the time to investigate further. He's too busy trying to figure out where to park all those VW diesels he's been buying back.

So I suggest you take the car to an air conditioning specialty shop. Let them diagnose it, and ask them to check the high pressure switch, too. The switch is cheap. But even if they confirm that you need a compressor, get an estimate from them. Who knows? Their price might be cheaper than the dealer's. Good luck.