Ok, I just opened the meter...

There are two paper fuses inside, and neither one had continuity...

Also, there a wire at the top that's broken... That wire is literally almost as thin as a hair..

I don't know what all that means, but the meter still beeps when I put it in continuity mode... But when I tested those paper fuses, it didn't peep. So I guess they're burnt.

The broken wire on top is strange, I've never seen such a thin wire.. At first, I thought it was a stray hair that got in there..

But, even as it is, it still measures voltage at the battery just fine.

fwiw, it's a Klein MM200..

 

Ok, after sitting for about an hour with the battery disconnected, I hooked the meter up to the negative terminal again, and now it only shows a 0.11 mA draw... down from 0.13 mA earlier...

So I checked the battery voltage, and it's down to 12.31 V... But it was at 12.4 just a little while ago...

I'm starting to think I might have a defective battery? It was new in January, and the water levels are full, but I know that doesn't necessarily guarantee that it's good.

I gotta go to the store, but when I get back, I'm gonna check it again, and then disconnect it overnight. Then I'll check it again in the morning.

 

No no now, your just not understanding what you are working with.
The battery voltage is fine.
The battery has 6 cells at a full charge of close to 2.15 volts per cell. 6 x 2.15 = 12.9 volts open circuit. or right after shutdown.
Since there is a drain, the battery voltage will normally drop as it sets.
The fuses in the meter are their to protect the meter and circuit board from being burnt from to much current in ….that.... mode, not in the voltmeter mode. You NEVER measure voltage using the meter Current hookup and setting.
You have to understand these things or let a shop do the work.
I never do current measurements on a high draw issue for just this reason. Saves meters from the unknown...
Better to use a small 12 volt interior lamp in series and watch the brightness drop when the drain is located and removed.
It does not burn anything up.

 

7:45 pm... back from the store..
... battery shows 13.92 V while idling, and 12.52 V with engine off and both terminals disconnected.

The trip to the store is less than a mile, all backstreets, but the battery charged up pretty fast.

fwiw, the amp gage on the dash always did look kinda high.. It's hard to say for sure because the range goes from 8 to 18 volts, so the center should be 13 Volts, right? ...I've been watching it lately, and my best guestimation is that she runs at 15-16 V on the highway.. the needle is always above the center..

 

Thanks again Bluegrass... I typed my previous response before I read this...

Sometimes you explain things in such a concise way that I have to read what you said a couple times before I understand it... and sometimes I have to google parts of your comments too...

I wish I could just invite you over for a BBQ and have you figure it out for me I'm sure you'd make short work of it.

But anyways, the battery is all disconnected now, and I'll check the voltage again in the morning.. What would you expect the voltage to drop down to overnight?

 

When you say "Current" I guess you mean Amps? (I had to google that)...

I'm still learning a lot about all this stuff, but it's been decades since anyone else ever worked on one of my vehicles.

OK, maybe not "decades"... I had the transmission rebuilt at a shop, about a year and a half ago... But, aside from that, I do everything myself. Sometimes I lose, but I usually win in the end. And I always learn a lot from it, either way.

If I burned up a $50 multi-meter, I'll consider that to be an acceptable loss and a cheap lesson.

But it's not likely that I'll ever take this F150 to a shop again. I'm gonna just milk this baby as long as I can...

 

Current is measured in amperes or sub fractions of same in milliamps microamps etc. (Ma, uA etc) as marked on the meter.
Voltage is measured in terms of Volts. millivolts , microvolts etc. (mv, uV, etc) as marked on the meter.
.
To measure current, the current has to pass through the meter to measure the flow in the case your trying to do.
There is another way but not applicable here, for the most part.
Voltage is measured across the Voltage source..
You can see from this that a measure of current that is too high for the meter setting will damage the meter. This is why a fuse or fuse link is provided in the instrument.to offer you a second chance to use the meter when the fuse is replaced. Should be a learning experience.
.
Measuring voltage too high for the setting on an "Analogue meter" often ruins the meter needle movement.
On a Digital meter that is 'auto ranging' usually does not result in any damage.
.
Most batteries after charging will show a higher voltage for a short time after, then slowly 'self' discharge to it's normal per cell level.
After that, the self discharge is by other means and should be quite slow...providing no cell has a fault such as an aged battery with lead dropped off the plates and built up on the bottom shorting the cell plate electrically to cause low capacity and discharge. then you have a slow or no crank
condition.
Disconnecting a battery then measuring the voltage only has limited value unless your looking for a battery defect such as described above.
Best way to look at battery capacity without a load tool is a voltmeter watching the voltage before, during and after cranking/starting.
There are cheap LED units at the auto store already calibrated and marked for use in the example below..
You need to understand the actions you see for it to be useful.
.
Example;
A. Before cranking V= 12.5.
B. During cranking V falls to 11.
C. After motor starts V = 15 or a bit higher.
What are you seeing?
a. The battery voltage before any cranking load.
b. The battery capacity drop due to the high load.
c. The charging system working to restore the battery charge.
d. How long it takes for the battery to restore to the alternator 'float' point of about 14 volts. This is determined by the health of the battery.
e. A look at B above that drops further is a sign of problems with either the battery or excessive loading from the starter or engine..
f. A battery with one or more bad cells will NEVER recover charge. This keeps the alternator outputting charge current at a higher level all the time, wears the brushes, over heats the alternator, boils water out of the battery too quickly, results in head lights and other lighting to change brightness with engine rpm and pulls down gas mileage from the extra load the alternator continuously puts on the motor.
Do read this enough times to get the common sense connections for each part.
And we have not addressed how the Alternator controls the charge function in a fault free system or the dash charge lamp indicator..
Good luck.

 

Right on, Bluegrass! Once again, thank you very much

Your description was clear, I understand it all much better now..

I just hooked everything back up, and I watched closely as you described.

The battery showed 12.23v before connecting it, and 12.08v after it was connected.

When I turned the key to the on position, it dropped down to 11.89v

When I started it, it dropped to 10.47 for a split second, but it immediately jumped back up, and was up to 13.9 in about a second or two. A few seconds after that, it settled in at 14.03

I filmed it to make it easier to review the details...