The Stovebolt Site Forums The Shop Area The Electrical Bay Electrical again - battery drain

Put a new battery in my vehicle and after not driving it today it would not start. I checked it with my voltmeter and it read .03V.
I jumped it and it started okay. With engine running at idle it showed 14+/- volts. Tried to start it later and it was dead. Voltage read .05V.
I checked lights, radio, heater, brake lights and all switches were off.
It must be a drain somewhere and I wish I knew where. And would it be the POS or GND which would cause that sort of drain.

it'd have to be the pos - disconnect the batt and get it charged properly, reading with that same meter - hook up the ground terminal only - do not use any corrosion preventive gunk on the terminals - put an ammeter from the + post to the battery cable and see if you read any current flow, if not there's something else going on

Bill

Will give it a try tomorrow. Thanks Bill.

Exchanged the battery. Put the ammeter as you suggested and getting zero reading. That would say that there is nothing draining from the batteey - correct?

right, has to be something else if you don't see any draw and the battery still goes flat - if it's a gen/reg system, maybe the regulator points sticking, not sure if an alternator can do a similar thing ... I know it's a new battery from previous problem, but are you positive all the connections are 100% and there's no cable that could have some corrosion under the plastic?

thinking about it, it's odd if your battery does get below 1v and will still come back to life - the 14v you read with it running should just indicate the charging system working, might not actually be getting charged up - and it does take quite a time running to charge it full

a temporary way to deal with it is to disconnect the pos cable after use until next you want to start it, the battery shouldn't be able to die disconnected, and if it does then it has to have a bad cell that won't hold a charge - also watch if there's any spark at all when you connect the pos cable, that's not a good thing, but then you would read some amp draw with the meter

Bill

Electricity is not my strong point obviously. I took a test light with the probe and alligator clip and tried it on the POS battery post and cable. Light shone. Of course this could mean nothing.
The cables are fine with no corrosion, I've cleaned the grounds and any accessories except lights turn off with the IGN switch.

Leave the ground cable connected and remove the positive cable, and just tap the cable to the battery post. If you see a small spark, there's a parasitic drain. If it's drawing enough current to make a test light come on full brightness when connected between the battery post and the cable, the battery will be drained overnight, or within a few hours. Start disconnecting circuits or pulling fuses one at a time until the light dims considerably or goes out, then trace that circuit to find the source of the drain. Start with the big 12 volt output lead of the alternator- - - -a leaky diode is the most common cause of parasitic battery drain on an alternator-equipped vehicle. Even with a bad diode, the voltage output will be right, but the charging current capacity will be drastically reduced.
Jerry

Found it! As I do not drive it at night and would have noticed it, the 2 courtesy lamps under the dash were on. I had not driven the vehicle for 4 days and with the lamps on it drained the battery.
Why they are on is the next question. Obviously an electrical 'gremlin'. The only light control is from the push/pull light switch. Anyway as I do not drive it at night I pulled those two bulbs.
Thanks to all.

I had an old jeep that did the exact same thing, turned out to be the light switch itself, never thought it would be that but there was some kind of short in the main switch for the lights,,