It is probably a failing Alternator not recharging your battery. Start the engine
and probe the battery with a voltage meter. Should be 13.5v to 14.5v.
Today my F250 died a few times. Dash Volt gauge showed low. Running voltage
showed 11.5v with my meter. I swapped out the Alternator and found 14.5v.
Good as new!
Cool, a guy that used a meter to find electrical trouble!
Suppose there's just one guy in each state in the US that actually does that? ;)
Here's my way of doing it...
1) It's messing up?
Don't mess with any wires etc get the analog meter out -first- -thing-!
That's so you won't "clear-up the trouble on yourself" and then not -know-
what needs fixing. BTDT and BTSeenThat! Do yourself a favor and -let- the
voltmeter do its job before you go monkeying with it. ;)
2) Read the battery voltage by digging the voltmeter's leads into the
battery's terminals (not the clamps ok?). Should read ~12 volts.
3) Have a helper try to start the vehicle. I've done this by myself, so don't
tell me you can't too. ;) But a helper's cool you can teach the helper how
to trouble shoot a starting/charging system while you're at it. ;)
4) Watch to see how far down the needle goes...
Less that 10 volts and sounds sluggish or don't turn over? --->*4a
Don't move really, stays at ~12 volts and don't turn over? --->*4b
Drops to ~11 volts and starter sounds good and engine starts fine? :)
5) After it starts, does the voltage stay at ~12 volts or rise to 13+?
If it just sits there like Seattle's did you got charging circuit trouble could
be the alternator or the voltage regulator or both.
(alternators can be fixed, BTW;)
The trick is to first try it on a vehicle that's working fine to see it in action.
An analog voltmeter is all you need.
*4a) Typically you've got a good connection through the whole starter's
circuit and got a low or weak battery.
How old is the battery?
A new battery can be bad BTSeenThat, no kidding.
*4b) Typically you got an "open circuit" (as opposed to a "short circuit")
and the analog meter will find it for you if you-let-it-lead-you to it.
In steps, move the leads closer to the "load" (the starter) until you get
virtually-zero-volts (when the helper tries to start the engine). Use little
bitty steps as you narrow in on -exactly- where the open circuit is. ;)
When hunting down a broken rail at night I'd count how many times I'd
put the meter across the track and read the track voltage (~3/4 volt DC).
If the circuit had an open in it, it'd read either ~1.25 volts or zero volts,
depending on which side of the "open" I was on. 7 times was the goal.
(Law of diminishing returns)
I put the meter down 0 times to 9 times, the track circuits could be five
miles long. Did this a jillion times, usually cold weather so I'd make a
fire for the track department guys to warm up by when they got there. :)
One time I put the pickup's spotlight on the tracks where I was going to
take the first reading and the broken rail was in the spotlight. LOL :)
(Cavot Road at the Arizona/New Mexico border, between Steins and Vanar)
(it got missed spelled somewhere along the line it's pronounced Steens)
Alvin in AZ
ps- is the PO's starter getting hot?