I don't have an ammeter - can I check a current drain by measuring continuity

[XH29N0G]

My multimeter doesn't have an ammeter, but it can measure resistance and I have a parasitic drain on the battery that I am trying to track down. 

Will it work to measure resistance, and then divide 12V by the resistance to get the current drain?  V/R=I??

How much current drain will drain a battery? 

[b5blue]

  Just disconnect the + cable from the battery and use the DC Volts setting closest to 15 V range. Put the red (+) lead to the + battery post and black (-) to the end of the cable that was attached to the + post. Depending on the car, charging system and optional things added you may need to disconnect or jimmy a few things like clock, memory supply to radio, door jam dome light switches and alternator before you can test the rest of the wiring for a short/drain. 
  If you do all above and still show a reading of any voltage (The dome light jam switch disable is so you can get inside with the doors open to test without drawing power.) one by one you pull a fuse and check the meter for 0 volts to isolate what wiring has a draw.
b5

[XH29N0G]

Thank you. 

I have it isolated to two fuses that result in changes of resistance through the circuit.  My knowledge is lacking as to how much of a drain is too much for a battery to sustain (in amps or volts, or (?) ohms across a circuit). 

I can switch to using your method.  For that I take it something like 0.1V is the limit of what can be detected.  Is this what you mean? 

Thanks

[b5blue]

 12V DC @ 1 AMP will read 12V DC @ .5 AMP or 50 AMP on a meter's DC Volt scale. Yes the amount of AMP draw will effect how fast you'll discharge your battery. The point is there should be no drain, find the drains and the item will, by nature of what it is tell you the rate it draws. 

[XH29N0G]

I'll bring my ammeter from work.  My system here only does voltage and ohms. 

My thinking was that if I had a leak with 120 ohms resistance that would be about 0.1 amp drain.  I am guessing something of this order is high enough to drain the battery, but just don'e know enough about car batteries.

[b5blue]

Typical car battery has a 500-750 amp hour rating, a 1 amp drain would take 500-750 hours to discharge the battery completely. (In theory)   

[XH29N0G]

Perfect, Thanks.  This is exactly what I was looking for.  Sorry for not asking this in the first place.

[mhinders]

A car battery is normally around 75 Ah.
And yes, a 0.1 Amp leakage current will drain your battery in 1-2 weeks. You will need an ammeter to measure the current.
In theory a voltmeter could be used only if you know the exact circuits and component values inside the volt meter, and thus be able to calculate the current flow.

[b5blue]

Yea find the draw