I picked up a DTAC Plus last winter for cheap with a broken printer and it has been working well until the last 2 times i tried to use it. I connect it to a battery that's at 10V according to a multimeter and it says no connection so i put it on the trickle charger for a few minutes to get it up around 11V. Charger finally sees the battery, but when i try to charge it with the DTAC it goes up to 14V and just sits there not outputting any current. Wait about 5 minutes and relays start clunking on and off in the charger. Any ideas what i have done to deserve this?
I don't know about the specifics of your snap on charger, but it sounds like the battery is sulfated. We bought a modern smart charger and this problem arose. Does the charger have an override button or maybe a jump start feature? Need to pump in more volts until the internal resistance starts to rise. Try a different battery to be sure. Google sulfation and surface charge to be educated on the topic.