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Old 05-19-2019, 05:55 AM   #1
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Electrical draw

On the road in Newfoundland. Had loop 1 in Gros Morne National Park’s Green Point Campground all to ourselves, on the water.

Trying to figure out what is drawing the chassis battery down overnight. Set the dmm to “A”, put the leads in the “com” and “v, mA, ohm”, etc. ports, pulled the wire off of the alternator, held one contact to the alternator and the other to the alternator post, got a zero so I ruled out the alternator. Right? In the meantime, I am just disconnecting the battery at night.
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Old 05-19-2019, 06:38 AM   #2
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On the road in Newfoundland. Had loop 1 in Gros Morne National Park’s Green Point Campground all to ourselves, on the water.

Trying to figure out what is drawing the chassis battery down overnight. Set the dmm to “A”, put the leads in the “com” and “v, mA, ohm”, etc. ports, pulled the wire off of the alternator, held one contact to the alternator and the other to the alternator post, got a zero so I ruled out the alternator. Right? In the meantime, I am just disconnecting the battery at night.
I'm assuming you're were trying to check for a resistance reading to ground through the alternator. In this case you would want to use the section of the meter labeled with the ohm symbol which resembles a horseshoe.

Brad
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Old 05-19-2019, 11:02 PM   #3
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This might help. I think it should work, but Brad can probably put me straight on the logic (or lack of!)

Switch off the Motorhome and disconnect the coach batteries to take them out of circuit.
Hook up your test meter to the chassis battery, measure the current draw.
Switch off the steps, fridge control board and the LPG detector which usually draw minimal phantom power when the coach is off.
Measure the current - is something still drawing some amps?
If so, have someone pull the chassis fuses one by one while you measure the current draw
Try and isolate the circuit which is drawing the current. That might give you some pointers as to where the problem lies.
If nothing is drawing current when you start the tests, it suggests that the items drawing phantom power are killing your starter battery.......which might mean it is in need of replacement. Check the draw on each of those items.

Hope this helps
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Old 05-20-2019, 04:47 AM   #4
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Thanks to both of you. I was trying to measure amperage draw but was using a port with the ohm symbol so hopefully the alternator is indeed off the hook. Will keep fumbling around as weather permits, watching ice float by at St. Anthony this morning and wishing my furnace worked better.
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Old 05-20-2019, 07:06 AM   #5
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Ohm setting measures resistance. Should only be used for a dead circuit. Using the ohm setting when a circuit is powered will blow the fuse inside the meter. Also, the ohm setting depends upon having a good battery in the meter.

Voltage settings (one for AC and another for DC) measure volts. Should be hooked up in parallel with a live circuit.

Amp setting (if available) measures current flow. It should be hooked up in series with the circuit. Some more expensive meters have induction sensors and can be clamped around the wire. Very few low cost meters have an amp setting that is useable for anything except very small currents.
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Old 05-20-2019, 08:34 AM   #6
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Steve, for some reason I thought I had read that you disconnected the batteries and and then was testing, my mistake. It sounds like what you were trying to do is check to see if there was a current draw passing through the alternator when the engine wasn't running.

In this case you would want to use the amperage setting on the meter with one meter lead connected to the alternator output stud and the other connected to the alternator wire. With the ignition switch off there should be no reading on the meter.

Brad
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Old 05-21-2019, 12:29 PM   #7
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Originally Posted by Waipio Rim View Post
Thanks to both of you. I was trying to measure amperage draw but was using a port with the ohm symbol so hopefully the alternator is indeed off the hook. Will keep fumbling around as weather permits, watching ice float by at St. Anthony this morning and wishing my furnace worked better.
It is possible to fry a meter like that, though leaving in in the amp port and trying to measure voltage is pretty much guaranteed to melt something (might have done that once or twice)

Sounds like you're on the right track, just write down all the things you check, and sketch out a diagram of all the systems, and rule things out logically
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Old 05-25-2019, 08:51 AM   #8
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Electrical draw

All is well. Either it fixed itself, or I fixed it when I 1) repositioned the ignition switch, which had been spun about 90 degrees clockwise by an enthusiastic person at the storage place n Halifax, or 2). ran the generator. Think I have the series/parallel thing figured out, too.
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