Electrical Help

[Scotstag]

Hello all,
My battery was dead, I charged it overnight,went for a run the next day,everything seemed rosy(voltmeter at 14,that is,l between 13 and 15!). But,the next day battery was dead again. I bought a new battery , removed the boot and the map reading bulb,and the same happened as above. I charged up the new one. Thinking there was a short somewhere I removed all the fuses from the fuse box. I then checked with a circuit tester to see if there was current flow between any of the terminals with the ignition off. What I found was no light on the tester whilst bridging the terminals but with the crocodile clip on the bottom terminal of fuse 1 "battery control" all the other top terminals lit up the light in the tester.

Should this happen ?.

Then still with all the fuses out I turned on the ignition and was surprised to see the ignition light and handbrake light on the cluster on. the electric windows also worked. But the biggest surprise was that the engine started the ignition light went out and ran fine although the rev counter didn't work.

If anybody is still reading , is this normal and what could be running down the battery?


Al.

[wilf]

IIRC, fuel pump and ignition circuit is not fused on a Stag, so being able to start it with all the fuses out sounds OK.

There obviously is a current drain when the ignition is off, from what you say it might be in the alternator charging circuit.

Have you tried seeing what current flows if you take off a main battery connection and use your multimeter to bridge that gap?

[Scotstag]

IIRC, fuel pump and ignition circuit is not fused on a Stag, so being able to start it with all the fuses out sounds OK.

There obviously is a current drain when the ignition is off, from what you say it might be in the alternator charging circuit.

Have you tried seeing what current flows if you take off a main battery connection and use your multimeter to bridge that gap?

Thanks ,Wilf, when you say "take of a main battery connection" do you mean the positive or negative terminal lead and connect the meter from the lead to the battery post ?

Thanks,
Al.

[wilf]

Yes, turn off ignition and do just that, what you read will be the residual battery drain that is causing it to flatten overnight. If you see a current flowing of a small number of amps, try disconnecting the alternator main plug and see if it stops. If it does, then the culprit will be a faulty voltage regulator. If it doesn't, then you need to try disconnecting other circuits until you find the culprit.

A faulty alternator voltage control circuit that won't shut down could cause a fire, so if you do track it to that, don't reconnect the battery/alternator again.

[Scotstag]

thanks,

doing this the meter ,set to DC Battery, goes off the scale, same as if I connect it directly across +ve and -ve post on battery.

I have a 1972 and the voltage control is bolted to the offside wing.

[Stag therapy]

Are you using a multimeter or a circuit tester? DC battery and the comments "off the scale" suggest the latter not the former.

Baz

[rac]

To check for battery drain you need your meter connecting between the removed + battery cable and the battery.Meter needs to be set on "amps" not volts,just be carefull though cos some multimeters only read milliamps others up to perhaps 10 amps-need to check the meter range.

[wilf]

Yes, the meter should be capable of reading at least 10Amps.

[Mike Stevens]

It's probably a bit safer to remove the negative battery lead and then measure the current between it and the battery -ve post. Less likely to create 'spits and sparks'!

Cheers,
Mike.

[Scotstag]

Thanks for the help and advice,

I checked the amp drain with a multimeter (thanks stag therapy) and got 2.8amps. I removed the wing mounted regulator and cleaned up all the alternator wires and checked the amp drain which was .002 so I thought I had sorted problem. Next day FLAT BATTERY!. I slaved started 666k and went a long run. Once back home I opened the bonnet and tried to start the engine, but battery was dead!. I disconnected lead to check for amp drain and found it still there. When I reconnected lead I heard a hissing sound like bacon frying.
Lead off no sound ,lead on hissing sound.
I traced it to the thick cable from the starter motor lying against the bellhousing, guess what? the insulation had burnt through and was shorting against engine.I don't know if it was a recent thing or it had taken since 01/06/1972 to melt.

Thanks again for all your help , problemm now sorted.