IDENTIFYING SITE OF DRAIN ON BATTERY

[ronwilson]

Got a continuing problem- a battery losing charge when alternator not feeding it. Anyone got a simple procedure to identify the location of the culprit ? and what tools would be needed to do this ? All help welcome.

[NZJLY]

Try disconnecting it overnight. If it still goes flat, then it is the battery. If the battery is OK, it will be working your way down the list of possibilities.

If it is running down slowly I would assume a power drain not a short circuit, which has to be a plus, but try the battery first.

[ronwilson]

Thanks NZJLY,
Battery can stand up to the overnight test, so I've taken that means I've got a power drain somewhere. Any advice on where to start trtacking it, and with what ? Ron

[Bullmansboy]

You need an ammeter, many of the voltage testers have this feature.

Disconnect each wire from the fuse box in turn and connect one lead from the ammeter to the wire you've disconnected and the other to the fuse box terminal (from where you disconnected the wire).

You may have to use different settings on your ammeter (always start at the highest, amps and reduce down to mA).

No needle movement (in your case is good news) no current been drawn from your battery. Reconnect and try another wire until you find which wire has current (indicated by needle movement) flowing down it.

You then need to find out where that wire goes.

All are colour coded, red/green, purple/black etc. So if you look in the back of a manual you can trace the culprit.

Sorry for been long winded.

[NZJLY]

Do you have any after market add ons? eg radio, indicators etc. I would check those first, as someone may have taken shortcuts on the wiring ;) Just like me

[chrisd87]

If you have a radio then this may well be the culprit. I had a similar problem to you when I first fitted mine - I traced it to the clock in the radio draining the system. Fitting an in-line switch solved it.

[ronwilson]

Thanks Chrisd87, again NZJLY, & Bullmansboy. Excellent tips-will find (beg/borrow) the ammeter and get to work on the process. Got a few add-ons incl. radio that could be culprit.

? for Bullmansboy: Can you intercept the power leads at/near the devices to get a better pinpoint on the drain ?

Cheers, Ron

[Alec]

Hello Ron,
it is only necessary to connect the ammeter at one point, and an easy one is where the main power lead comes off the starter solenoid (large brown cable). Connect the ammeter between the spade terminal on the solenoid and the disconnected brown lead. If there is a drain then the meter should read some current, start disconnecting in an organised way until you see the ammeter drop to zero, that then is your drain.
Normal drains are things like boot or bonnet lights but not normally found on Minors. Alternator, if you have one is a possibility so unplug that also.

Alec

[bmcecosse]

It's almost certainly the alternator - so just unplug that one night, and see if the battery is still up in the morning.
Edit - Sorry Alec - just read your post properly after sending mine - I see you suggest alternator - and I bet it is !

[Pyoor_Kate]

Another perenial favourite is the 'modern radio'. Quite often these go into standby not 'off' and are always drawing a small amount of current. If you're not using the car that often these can be enough to quietly drain a battery....

[Bullmansboy]

Hi Ron

Sorry for delay in getting back to you, other have given answers to your question in my absence.

Delay due to picking up my "new" moggy Series II Convertable. Something I've always dreamed about.

Hope you've solved your problem?

Regards

[ronwilson]

Hi Bullmansboy,

Congrats on your new treasure. Has to be a great feeling!

Have located a multimeter for use this next weekend on the problem but confused about the 'alternator' suggestions. Its voltage output has been up to the mark but will add that to the top of the list for disconnect when we can start working the problem. If that's the culprit, we'll have fun replacing that! Thanks everyone,

Ron

[bmcecosse]

The diodes in the alternator can fail and allow a small reverse current when the engine is not running. It's easy to pull the little plug out and then see if the battery is still 'up' in the morning.

[ronwilson]

Thanks bmcecosse for the explanation on the 'alternator' link. Will give it a go tomorrow after the battery gets a good charge. Ron

[KirstMin]

Try disconnecting it overnight. If it still goes flat, then it is the battery.

Ron, I dont see anywhere in the post how long the battery is taking to discharge? If it is taking more than 12hrs then leaving it overnight is not a valid test because it will still have some charge left in it. It could still be your battery and wouldn't do any harm to charge it up fully and take it to be tested (places will do it for free). Then at least you can be 100% that the battery is OK and move on.

[ronwilson]

Thanks everyone for the leads (no pun) on this problem. Did the duration test-first at 8 hours and then 24 hours. Engine kicks over in seconds both times-so battery itself probably OK. Using a light probe off the ground pole of the battery, picked up a dim light. Disconnected the radio, dim light remained. Separated the positive terminals and eliminated the alternator as source; did same for the starter. This left the power going to the terminals drawing from the non-ignition controlled lead.

Weren't able to easily isolate and track further so now feel it unavoidable to go back to the drawing board and unbundle the electrics which all feed thru the original 2 fuses. We have a new cable system purpose made to fit the alternator in the Fiat engine system with fog lights (front and back); to that we've added:-relay for fogs; -reversing light; -twin horns; -two speed heater; -heated rear windows with relay; hazard warning lights; warning bleepers for direction indicators & hazards; -steering wheel mounted controls for: direction indicators, 2 sp windscreen wipers with electric windscreen washer; headlight control with flash function;

Phew ! OK, we were lucky to create an operable vehicle ! Actually, if the car was run on a daily basis (with RPM up if needed in slow traffic ) it would have performed fine & has. It was the old garage time between use with battery fully connected that showed the weakness (& fire risk?) Now time to fit a fully expanded fuse system and add relays for horns and probably hi beam flasher.

Thanks everyone for taking the interest and time to give us the clues to pursue this and eliminate some important sources for power leakage (specially alternator). Thanks, Ron

[bmcecosse]

Hmmm - well,something is drawing power! What about the voltage stabiliser thingy for the fuel gauge - could it be constantly connected, instead of through the ignition controlled circuit? You don't have a battery voltage gauge connected, do you ? These draw current and so must also be through the ignition.

[ronwilson]

Thanks bmcecosse,

The fuel guage is definitely thru the ignition switch but there's other leads back there feeding instruments like voltage meter, oil & water temp guages. Hard to get to now; think we'll have to wait and make that part of the unbundling game. Probably take some time, but will post results in future when done. Cheers, Ron

[bmcecosse]

Ah - so you do have a voltage meter - that WILL be it!

[ronwilson]

bmcecosse,

Haven't removed the instruments from the dash yet, but
what aspect of the voltage meter do you reckon could be causing the drain ?

Thanks, Ron