Replaced the alternator 4 times in 2 years

Nah..that's way too high a setting Steve...you're expecting to see a MUCH lower figure, ALTHOUGH he could set it to 10 Amps initially, then if he sees no reading he should select progressively lower settings till he gets a reading near half scale...You should (normally) see something like...oh, I forget now but like maybe 10 to 15 mA?...lessee now ...100 mA is 1/10 of an Amp, so 10 mA is 10% of that or 1/100 of an Amp...that sounds reasonable to me...isn't it?...

10 Amp setting only means that's the maximum reading the DVM can handle, not the minimum, its a four digit display so with that setting it can still read into the 10's of millamps (with poor accuracy, but we don't care for this problem). If the display only shows 3 digits we can still read in the 100's of millamps.

In any case a typical car battery is rated at about 50 amp hours, meaning if the car battery is dieing overnight the short has got to be pulling some serious current, 10's of milllamps isn't going to kill it. Even 100mA at 24 hours is only going to suck 2.4 amp hours out of the battery, still not enough to kill it. So the short is probably in the amps area, or at least several hundred mA. I would think if the battery has 30% of its life in it it will still start the car (wild guess).

Car headlights draw about 10 amps a pair, for instance, on low beam. The best sears diehards are rated well over 100 amp hours and will still start your car if you leave your lights on overnight in the winter (remember those old sears commercials with a car frozen in a block of ice with the lights on). Anyway, an exposed wire shorting to the chassis pulling a few amps could be the cause, or maybe a shorted power window motor, or shorted door lock solenoid, if its a relay embedded deep inside your dash, you done for! (unless you go to the disconnect your battery every night routine).

While I can agree with most of what you say there's a few zingers in there...like leaving the headlights on overnight...I realize that the figures stack up that way but just try it yourself (make sure that you have a friend primed to come over to boost you first though)

What I was referring to was a bad battery which can't handle even the slight current that modern cars draw when shut down. And I've had new batteries like this...

Also what you say about digital VOM's could well be true, not so with analogue units though...I hate digital VOMS, never use them...

Well I didn't say I had a Diehard, so I wouldn't try it, I just looked up mine, its 48 amp hour (Walmart $39 cheapo), so lights at 10 amps hour means I got probably 3 hours, give or take. I probably couldn't make it parked at a baseball game with the lights on, let alone overnight.

Oh, ok, I didn't think about that.

Really? They are so nice, big digital numbers to read, easy on my old eyes.

Well, it's like aircraft instruments, the analogue types are much better for 'transmitting' data to the human brain than digital types because a glance will impart an approximate value almost instantly just by the needle position where a digital readout needs some slight mental gymnastics to impart the data.

Some instruments include a digital readout right on the face of the analogue gauge for extreme accuracy when required.

In any case, I've become used to the analogue type and find it easier to use...I agree with you though that the digital likely will measure low values better (when the range is selected much higher)

I don't do much electronic repair now (unlike in the past) my poor old eyes aren't what they once were... :)

You don't need those exact lamp numbers, anything you have on hand that has the right voltage and wattage will do. You just need to look up the ones available on the spec sheets in an auto lamp catalog. (This is the thick book the parts man uses that has the bulb specifications, not necessarily the one that tells what lamp goes in each car. Though I've seen both sections printed together in one big book.)

The book will either list the current draw of the lamp, or you can get a very close idea with the wattage rating of the lamp and a bit of math - 55 Watts divided by 13.8 Volts = 3.9855... Okay, 4 Amps. With that lamp connected in series with the meter and the chassis ground even if someone tries the starter only 4 Amps are going to go through

- the meter will be fine.

Or the reverse Volts X Amps = Watts. Google "Ohm's Law"

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