I've had 2 or 3 GM ones (possibly 4 - not sure) fail over the years. Enough so that I carry a couple of spares if headed out for a long trip. But, I only need to worry about horizontal (not vertical) movement of my conveyance. Later, JR --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com