HOW TO USE A MULTIMETER

[Jorge022770]

Guys, I got a new voltage regulator and the 2-month old battery is fullyh charged. I got a digital multimeter so I can perorm the test and know if my bettery discharging problem (see Electric Gemlins posts by jorge022770) was the regulator, alternator, or any other electric draw.

The problem is that this multimrter has very incomplete3 instructions, and I can't figure where to put the indicator to test charging of the battery by the alternator . It has V..., V, one has options of 200m, 2000m, 20, 200, 1000 then the other has 200 and 2000 with the micro symbol, 20m, and 200m. The third group has from 200 to 2000K,'

I am retarded and a big ignorant when it comes to electric issues, so it's ok to laugh at me now....but please, help me so I can do this thing right.

Jorge

[RoadsterYosh1]

Turn the gage knob to the “DCV� side (it has 1000, 200, 20, 2000m, 200m on it, more or less). Turn it to the “20� that’s the range (0-20 volts DC) or something close to it. Plug the black wire to common ( - ), and the red wire ( + ) into the Volts, ohm, milliamp plug. Your now good to go!
Have fun multi-testing.

Yosh

[Jorge022770]

Yosh:
Thanks for the crash tutorial....I know what to do now...except for one thing I'm using the DC setting and wire plugging, right?

And the next stupid question now that I know what settings I need on the multimeter.......what do I connect them to to check if alternator is charging the battery?

Jorge

[glennhuff]

To test your alternator, just put the black lead on the negative battery post and the red lead on the positive battery post. It should show more than 12 volts. It should actually be 13.5-14.5. If you are showing 12volt, then it isn't charging.

[mikew]

Connect the black wire to the -ve terminal on battery. red wire to +ve terminal on battery.

With engine off, the alternator will not be charging, and the voltage across the battery should be less than 12V.

With the engine running, and all electrical devices (lights etc) switched off, the voltage across the battery should be higher than 12V (I think high 13's, low 14's). If so then the charging circuit is working.

Now for an extra test.... turn on your lights, driving lights, radio, and heater fan. What is the voltage across the battery now? If it above 12V all is good, if lower than 12V then your alternator cannot keep up with the load (it cannot power all of those accessories and still charge your battery!), and your battery will slowly be drained while all of those accessories are on.

Mike

[Jorge022770]

Mike and GlennHuff:

I appreciate your big help. What would have happened to my roadster if I didn't have guys like you willing to share your knowledge!...that goes to all the gurus that have walked me through the journey...

...and Yosh: the multimeter now is not a mystery thanks to your help...thanks!


Jorge

[dbrick]

Also, you can use it to find the drain, if there is one. One of the most common slow battery discharges is acid residue on top of the battery. Put your meter on 20v dc scale, Put the red on positive terminal of battery.take the black lead and drag it around the top of the battery, in between the filler caps/covers towards the negative battery terminal. Don't be suprised to see a voltage reading of 1 to 6 volts or higher. If you see more than 1 volt, PUT ON GOGGLES!!!! Wet battery slightly with hose, pour handfull or so of baking soda to completley cover top and terminals of battery . It will turn brown and bubble up, maybe violently (hence the goggles). Add a mist of water to make a paste. Let sit a bit. Rinse very thoroughly, cover with baking soda again while still wet, If it bubbles up again, let sit and rinse off. Dry battery, retest voltage as above, will likley be lower or close to 0.

By the way, Sears has an excellent autoranging multi meter that goes on sale for $19.99 rather often...

http://www.sears.com/sr/javasr/search.d ... &x=27&y=12

[RoadsterYosh1]

Glad I could help. Wait till you have to use the other functions…
Here’s a few other tidbits about a 12 volt battery, when you buy a new battery off the shelf it should be around 13 volts, most are not though, due to parasitic loss from sitting around. If you can pick your battery, get the one with the highest charge, it’s the newest. It could look funny walking around with a multimeter in your pocket A good healthy charged battery will have 12.8v no load. if you have 12.0v with no draw, that battery is dead and won’t start an engine.

My service manual says the alternator should put out 14.0v @ 2500 rpm
yosh