Just grab a plug wire and have someone crank it while your holding on to the wire then you'll know if its workin http://free.***boat.net/ubb/biggrin.gif j/k I've often wondered the same thing I've had them go all at once and I've also one time had one just kinda half ass work, however this was on a four wheel drive truck and it got a little wet and muddy about a week before. I may be wrong but, couldn't you put a voltage meter on it....