power draw with ignition 'OFF'

[80's_delirious]

Over the last 4-5 days I have had my car parked while I have been working on it. I spent some time making up a new wiring harness and control relays for toyota electric diff locks, I spent quite a bit of time with the iginition on and also testing operation of difflocks while trying to identify an apprpriate signal wire for relays.

When I tried to start the car this morning, both batteries are dead FLAT(5-6volts on cranking). I went to swap out one battery with another deep cycle, as I connected up the battery it arced out quite strongly as I touched the lead to the terminal.

Ignition was 'off'.

I have disconnected all new wiring, and checked that I haven't created a cross feed some where. It all seems OK.

Am I right in thinking I shouldnt have any power draw from the batteries with the ignition and accessories 'OFF'

any suggstions of what to look for? or check?

[DamTriton]

Usually not zero current but minimal current draw, in the order of 10-30mA being the clock module and security/central locking standby currents.

Disconnect any dual battery system you have connected and go back to standard wiring. Put an ammeter in line between the battery +ve terminal (red lead on ammeter) and the clamp assembly (black lead on ammeter) with the ammeter set to 10 amps initially (in case of major load) then scale down to the 200mA range until you get a reading.

[80's_delirious]

it has two batteries as standard, but connected in parallel (12volts)

I have disconnected tha battery leads linking the two, but no difference.

current is definitely more than what would be used by clock, central locking etc

can you read amps with a multimetre?



I have pulled fuses on the circuits I have been fiddling with, and still quite a bit of current draw.

[ledgend80]

get a clamp meter if you can to measure your current draw.

[80's_delirious]

Ok, stupid question time

even if I can measure the current draw, how does that help me figure out what is using power? how can I use this to diagnose what is wrong?

[DamTriton]

it has two batteries as standard, but connected in parallel (12volts)

I have disconnected tha battery leads linking the two, but no difference.

current is definitely more than what would be used by clock, central locking etc

can you read amps with a multimetre?



I have pulled fuses on the circuits I have been fiddling with, and still quite a bit of current draw.

Yes you can.

But first if you are really sure it is drawing a LOT of current you can test it by using an H1 headlight of 55 watts between the positive batt terminal and the load, if it glows you have close to a dead short or a significant enough current to not need to be fussed with a DMM to read it (greater than 4 amps). It is a major problem.

Next diagnostic check is to lift the big terminal on the alternator and recheck using the procedure above then if needed below, if the current reduces then you probably have a bad diode in the alternator (not unheard of).

A guide for the use of the generic "yellow" DMM's available in most K-Marts/Supercheaps/etc to measure current...

You will see on the scales at about the 4 o"Clock position a selection marked "10A". DO NOT CONNECT ACROSS THE BATTERY + AND - IN THIS POSITION!!! To use this position you need to use the upper of the three sockets for your positive lead and the lower of them for you negative lead. Put the DMM in line between the battery +ve terminal (red lead on ammeter) and the clamp assembly for the +ve terminal (black lead on ammeter) with the DMM set to 10 amps initially (in case of major load) then scale down to the 200mA range until you get a reading. If it shows less than "0.200" then you can select the 200 mA scale. Do this by clicking the dial anticlockwise one click around to select the "200m" in the "DCA" arc of the selector and placing the positive lead in the middle socket. If it reads less than "0.020" then you can click around anticlockwise to the "20m" scale and read off the amount.

Other than that a process of deduction as you have been doing. Pull a fuse and check current, if current unchanged replace fuse and move to the next one. After doing all the fuses start on the relays using a similar method, sometimes relays get stuck "on" passing current when they shouldn't be (not powered on)

[80's_delirious]

cheers Damkia, will see how I go

[80's_delirious]

it has two batteries as standard, but connected in parallel (12volts)

I have disconnected tha battery leads linking the two, but no difference.

current is definitely more than what would be used by clock, central locking etc

can you read amps with a multimetre?



I have pulled fuses on the circuits I have been fiddling with, and still quite a bit of current draw.

Yes you can.

But first if you are really sure it is drawing a LOT of current you can test it by using an H1 headlight of 55 watts between the positive batt terminal and the load, if it glows you have close to a dead short or a significant enough current to not need to be fussed with a DMM to read it (greater than 4 amps). It is a major problem.

Next diagnostic check is to lift the big terminal on the alternator and recheck using the procedure above then if needed below, if the current reduces then you probably have a bad diode in the alternator (not unheard of).

OK, have done this test, 55watt lamp lights up like a farking beacon

can you elaborate on the second check on alternator terminal? I put 55watt globe between battery pos and the alternator. it lights up instantly and stays brightly lit.

any suggestions on what to look for as a cause of dead short?

A couple of days ago, I accidently shorted a limit switch signal wire in centre difflock in the transfer case and closed a relay causing a fried actuator motor. I replaced this and it all tested OK, it was operational as per normal. I have disconnect all my non original wiring, it all tested OK and newly fitted electric diff locks were all seemingly operational, and are currently disconnected.

Of the standard OEM wiring etc, what could give me such a large current draw when everything is off?

[ledgend80]

the light bulb trick is great for finding shorts when you keep blowing fuse. saves blowing fuses and you can normally see if the light is still on. and then light goes out when you remove the short. gat the one from an auto elec. helped me out a few times.

[DamTriton]

it has two batteries as standard, but connected in parallel (12volts)

I have disconnected tha battery leads linking the two, but no difference.

current is definitely more than what would be used by clock, central locking etc

can you read amps with a multimetre?



I have pulled fuses on the circuits I have been fiddling with, and still quite a bit of current draw.

Yes you can.

But first if you are really sure it is drawing a LOT of current you can test it by using an H1 headlight of 55 watts between the positive batt terminal and the load, if it glows you have close to a dead short or a significant enough current to not need to be fussed with a DMM to read it (greater than 4 amps). It is a major problem.

Next diagnostic check is to lift the big terminal on the alternator and recheck using the procedure above then if needed below, if the current reduces then you probably have a bad diode in the alternator (not unheard of).

OK, have done this test, 55watt lamp lights up like a farking beacon

can you elaborate on the second check on alternator terminal? I put 55watt globe between battery pos and the alternator. it lights up instantly and stays brightly lit.

any suggestions on what to look for as a cause of dead short?

A couple of days ago, I accidently shorted a limit switch signal wire in centre difflock in the transfer case and closed a relay causing a fried actuator motor. I replaced this and it all tested OK, it was operational as per normal. I have disconnect all my non original wiring, it all tested OK and newly fitted electric diff locks were all seemingly operational, and are currently disconnected.

Of the standard OEM wiring etc, what could give me such a large current draw when everything is off?

Where on the alternator did you put the other wire of the globe? If it was on the positive terminal of the alternator then it is almost certainly a dead diode or regulator in the alternator (previous short you noted would be the most likely cause).

If you simply put the light between the +ve battery terminal and the ground of the alternator it would not be of diagnostic value.

Is it possible to separate the wires going to the +ve battery clamp? Of so try the lamp test to each individual wire.

[80's_delirious]

all sorted. thanks for the help

[DamTriton]

What was it, after all that???

[krusty182]

Found this. Which may not help in this instance, but might be handy for similar problems.

http://jaycar.com.au/productView.asp?ID ... BCATID=619" onclick="window.open(this.href);return false;