Won't turn on is voltage is under 12.9 volts - Garmin GPSMAP 740S GPS Sounder & Chartplotter 010-00835-03

Battery ? battery cables ? Test the starting system , voltage drop starting system ! go on you tube a check out voltage drop testing starting system .

With a voltage meter see how many volts are at the starter terminal. If not 12+ volts you have a bad connection. Check connection at the starter solenoid. Does it have 12+volts? Short the solenoid. Does it put voltage to the starter?

normally a quick clicking sound means that the battery is low in voltage and amperage,but first check your connectors and the battery posts to make sure they are clean and secure. if you have a tester,check for voltage at the battery,you should be getting 12 volts or more.if you have 12 volts+,turn on the headlights and test the battery to see if it is retaining 12 volts or not,this is known as a load test. if voltage falls rapidly your battery should be changed.if it holds charge pretty well,than put thr battery on slow charge overnight and retry starting the vehicule.nb. the clicking noise is caused by the onboard computer that reads the voltage before startup and under 11.5 volts your car will make this sound.if your car starts put the tester on the battery again and check voltage,it should be 13volts or higher which means your alternator is charging the battery.

Sounds like you have a low voltage problem.Take a volt meter and battery voltage first it should be 12-12.7 volts not running and key off.Then start engine and check the voltage coming out of the alternator it should be 13-14.7 volts.If one of these are not within these specs then replace which everone that is bad.

check the battery with a multimeter and make sure you are getting at least 12 volts, if its not showing any voltage one of the wires from under the plastic housing has become disconnected, if it is showing voltage but not 12 volts recharge it then check it again after about 12 hours and make sure it is showing 12 volts, if it isn't check your charger with a multimeter and make sure that its putting out at least 13.8 volts, if it is then you have a bad battery

You won't damage anything with 12 volts. Equipment built for use in automobiles will often have a DC input marked 13.8 volts because it's the voltage delivered by a fully-charged battery. But any supply around 12 volts will work. Just be sure the supply has enough current available (around an amp should be fine for a scanner), and that you get the polarity right when connecting it.

check the voltage of the battery,, it should be a little over 12 volts,, if not,, replace it

on a lot of plymouth acclaims ,there is no fuse marked ignition. what I would do is check for voltage at the ignition switch. if no voltage is going thru it. then the ignition switch is bad. check the wires from switch, and turn key to accy,then check wire. then turn to run and record voltage.

the battery says 12 volts but may be dropping to 4 or 5 under a load...i would suggest jumpstarting the car and see what happens.the battery should read in the high 12 volts and not less than 9.5 under cranking. the dash lights go out on your car when starting,and the alarm will go off ,and disable the ignition if the voltage is too low in cranking the car because the computer will shut it down and activate the anti theft.....check your battery posts are tight. best of luck