924Board.org

[sleepy]

I'v bought a multimeter to check the output of the battery when the ignitions off & pull fuses to find whats draining too much & causing the batt to slowly go flat (an exercise that ozzie was kind enough to explain in detail).
Only problem with my new, bright yellow, 32 position digital multimeter is........ -i don't know how to use it
if anyone could point me in the right direction i'd be hugely gratefull!

the positive test lead can be pluged into a 2A max jack or a 10A jack or a jack for measuring voltage ( V/something that looks like a doornob )

there are 5 sections of settings: A---, A~, V~, V---, the doornob pic.

Each section has settings like this: 10, 2, 200m, 20m, 2m, 200u, 20u.



I'd also like to know which setting i need to find which is the ignition wire & battery wire to connect the stereo.
All I know is that i need to read milliamps, I blame my ignorance on not being taught enough about electrics in school

cheers
-Sleepy
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meteor silver 1981 924 lux. -UK

[augidog]

[MunkPuppy]

Ok I think I covered this in another post, but I can't be bothered to find it, so here it is again, slightly abbreviated.

The "doorknob sign" you speak of is the OHM symbol, which is a measure of resistance (holding back current).

To check for which wires have power when the car is on or off is a simple task.
Set your multimeter to V--- with the red test lead plugged into the 10A hole.
With your ignition key set to off (or just leave the key out), check for wires that read approx 12 volts. (Don't bother checking brown wires, they're all ground wires)
Then, put the key back into the ignition and start your engine. Make sure that ALL accessories like heater fans, radios, defrosters, and such are off. Now, check for wires that read between 12 and 14 volts. (Don't bother checking the ones that read voltage while the car is off). That about does it.
Incidentally, if you get readings of lower than 12 volts while the car is off, either the battery needs charging or replacement. If you get readings of lower than 13v or higher than 15v while the engine is running, your voltage regulator may require replacement.

Hope this helps.
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'80 931 FOR SALE

"It's a shame that stupidity isn't painful"
-Anton Szandor LaVey

[MunkPuppy]

I forgot to mention, to check for battery drain:

Put the red lead of your multimeter into the 10A hole.
Disconnect the negative power lead from the battery.
Turn the knob of your multimeter to the 10A setting.
Connect the black test lead of the multimeter to the body (or the negative lead of the battery), and the red test lead to the negative post of the battery.
Then do as Lizard's ghost suggests, and pull fuses until the current load drops on your meter. There's your leak!

Here's a very recently posted link for fuses and what they... fuse. http://www.m-elliott.us/Porsche/FAQ_Main.htm#fuses
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'80 931 FOR SALE

"It's a shame that stupidity isn't painful"
-Anton Szandor LaVey

[Peter_in_AU]

to check for current drain, connect the positive lead/probe to the 2A socket and switch the doornob to the highest number in the A--- (DC amps) range.

Make sure the car key is off. Remove the negative/ground battery cable, switch on the multimeter and connect the multimeter between the battery negative post and the negative battery cable:

Battery -ve -----(negative meter lead)-----> Multimeter Ground/Common
Multimeter 2A -----(positive meter lead)-----> Negative battery cable.

Put a bit of paper, wood, plastic etc under the battery cable so it doesn't touch the body or any metal. A couple of alligator or bull clips will make it easier to connect the probes to the battery post and battery cable.

When you make the connection your multimeter will probably give a high reading (up to 500ma) as your CD player resets itself. Wait 15 seconds or so until the reading drops down and stabilises.

You can now turn the doornob rotary switch to a lower number (still within the A--- range) to get a more accurate reading.

Now check the fuses. Note what the reading on the multimeter is, pull out one fuse and check to see if the reading on the multimeter drops. If the reading drops make a note of the position of the fuse. Put the fuse back in and go an pull and check the next fuse.

If pulling out any of the fuses caused a drop in the multimeter reading pull out your Haynes and find out what that fuse is connected to.

If none of the fuses caused a drop in reading post the reading you get on your multimeter and we'll go on to stage 2.
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1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

[sleepy]

thanks guys. So am i right in thinking 10 is the highest reading, 200m is 200milliamps & 200u is something smaller.
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meteor silver 1981 924 lux. -UK

[Smoothie]

Yes, the "m" suffix is milli (1m = 1/1000 or 0.001), "u" (actually "µ" or "μ") is micro (1µ = 1/1,000,000 or 0.000001)

I never had a meter that was marked with the "---" and "~", but apparently "---" is DC and "~" is AC, so
A--- is DC Amps
A~ is AC Amps
V~ is AC Volts
V--- is DC Volts
and of course the omega symbol "Ω" is Ohms (resistance)
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[Ozzie]

Nothing to add here.
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Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

[kaffine]