My AC leaks and mechanic says it is shrader valve. Is it expensive?
A Schrader valve is a simple push valve used to keep pressure inside a container or system, while making it easy to add more pressure when required. The valve stems on your car's tires are Schrader valves. The PARTS to replace a valve are fairly cheap, but labor and materials to repair an AC system may run the bill up.
It is like the valve in a tire stem. No, it is dirt cheap - like four bucks if that. Why didn't mechanic just replace it? You can replace this yourself. Just go to a parts counter and ask them to look up your car and they will find a valve. Then ask them for the tool. You can probably get both for under $15. But you will have to wait until all the refrigerant leaks out of it hasn't already. You don't want to take out a valve from a pressurized system. You can also recharge the system yourself too. They now sell the hose that attaches to the can with a built in valve. It isn't difficult if you can follow directions.
It's cheap - even free if he's going to invoice you for re-charging the system. If he normally does A/C service he should have an extra one on hand. To replace it legally you would need a recovery machine to evacuate the system, replace the valve and then recharge the system. Probably $100. worth of service. To do it backyard style you'd put some gloves and goggles on, remove the leaky one and jamb the new one in while refrigerant is spewing out and then top up the system. Backyard style is almost impossible on a warm day because the refrigerant will be under high pressure, it would definitely make a good youtube video. If you did it on a very, very cold day (it stays in liquid form -15F), it would be easy because the refrigerant would be at a very low pressure.
