Sweating bullets over an aging or broken home air conditioner during our 90 degree spell? It gets worse. Due to coolant shortages, the cost of repairing any central air conditioner older than two years is going up, said Angie Hicks of Angie'slist.com.

Two years ago new air conditioning units started to use a non ozone-depleting coolant, R410A. The coolant that older units have, R-22, is no longer being produced. Prices for it have doubled in the last year, said Jake Barfield, general manager at Paul Falz HVAC in St. Paul. The price for the first pound is about $70 and $30 for subsequent amount at Paul Falz. For most coolant leak repairs, it's about $200 for the coolant, said Barfield. (It could be worse. Hicks said that some contractors are charging as much as $175 for the first pound.) Most a/c units hold between five and eight pounds.

If your a/c unit is running but not cooling enough to prevent a sweat, it could be low on coolant. About 25 percent of a/c problems are related to coolant, said Barfield. 

If you have a coolant leak, don't assume that you need a new central air unit. If the leak can be repaired, your a/c unit may have more life left in it, With many HVAC contractors stockpiling the old R-22 supplies, they're not in danger of depletion yet. On the other hand, if your unit is 15 years or older and it has a coolant leak, ask about new units. "They're more environmentally friendly and more energy efficient," said Hicks. 

Anyone been recently pressured by a contractor to replace an A/C unit that's only five to 10 years old just because of a leak? Get a send or 3rd opinion if you can wait. Most air conditioning contractors will be backlogged as long as the heat continues.