Dave8N in Pa
Member
Someone told me a bad alt. will drain the batt. How does that work? Anyone understand this? Thanks
- Thread starter Dave8N in Pa
- Start date
Dave8N in Pa
Member
Thank you sir. Any idea how I can test it, with a mutimeter?
Dave8N in Pa
Member
Yes I guess I could do that but If someone knows how to test it with a meter, I would sure like learn how. Thanks
Disconnect the ground clamp. Place a test light between cable end and battery post. If there is a drain,the light will come on. Easier still,Disconnect the battery at night.If you see a spark when you touch the cable end to battery post,you have a draw.Unhook alternator,if spark goes away,or light goes out,you've found the problem.
Dave8N in Pa
Member
Thank you sir, I'll try that.
Geo-TH,In
Well-known Member
Instead using a test light between negative post and ground cable, use an ammeter.
Start out on the highest scale and work down to the milla amp range. There should be zero amp draw. I bought a new 3 wire alternator and one of the wires was drawing 2 ma. So I ran that wire through ignition switch.
Start out on the highest scale and work down to the milla amp range. There should be zero amp draw. I bought a new 3 wire alternator and one of the wires was drawing 2 ma. So I ran that wire through ignition switch.
NO meter needed, disconnect alternator and connect an unpowered 12 Volt test light with a low wattage bulb between the disconnected wire and the alternator output terminal.
The light should at least GLOW if there's a battery current drain to ground through the alternator.
If an internally-regulated alternator (Delco 10SI, for example), you need to check for draw through the"voltage sense" terminal, and also verify that the voltage/current to the "excite" terminal gets shut off when the ignition switch is switched "off".
The light should at least GLOW if there's a battery current drain to ground through the alternator.
If an internally-regulated alternator (Delco 10SI, for example), you need to check for draw through the"voltage sense" terminal, and also verify that the voltage/current to the "excite" terminal gets shut off when the ignition switch is switched "off".
Dave in Tx
Member
Leave the alt hooked up and check in a couple hrs. It will be warm or hot if the battery is charged..
Traditional Farmer
Well-known Member
- Location
- Virginia
Go out at night take the + cable off and then tap it slightly (in the dark) against the + post on the battery if you get a little spark you have a draw on the battery.
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