Do you know what the service life of these unit is? 20 Hours. That is all. Most people only them 5 to 10 minutes at a time or 30 every week or so. Now some will last longer than 20 and some less. But they are rated at 20 hours. I showed a homeonwer the 20 hour service life sticker on his hand held blower tube and he almost cried. Most of the $100 or less stuff is rated from 20 to 50 hours. They are throw-aways. They were never ment to be worked on. A new coil will cost you as much if not more than a new unit.