AE82 - Electric Problem

[convert]

I have an 86 AE82 Corolla hatch with 4AC Engine.
I (think) I have a problem somewhere in the electrics.
Battery goes flat over a few days if car not driven. I have replaced battery same problem.
I have disconnected neg battery terminal, disconnected clock and then connected volt meter and get 12V reading.

I (think) I have traced the problem to the following point.
If I unplug and orange coloured plug from the back of the fusebox (one near internal driver side
'kick panel' - no longer get reading on Voltmeter.)
I have left the plug in and taken out all fuses from both fuseboxes and still get the 12V reading.
The orange plug has thick (compared with most other wires) which are
1. Light Blue
2. White (from memory there are two of these - I've put the thing back together now)
3. Black
It also has thinner wires
1. Black with white trace
2. Black with red or orange trace (bit hard to tell under there in the dark with a torch)

I think I am getting to the end of my ability with this. I have a gregory's manual but the wiring diagrams are beyond me.

I am thinking of installing a switch on the kick panel to "turn off" the offending wire coming out of the orange plug when I leave the car sitting for more than 48 hours. (That is if I can work out which wire it is.) At present I take out the 60A circuit breaker from the positive battery terminal when I park it for any length of time.

Any ideas on likely causes or fixes appreciated.

Regards

Convert

[Dale]

You are concerned the clock is draining the battery? I'm a bit confused what you mean, the clock should be on the dome circuit.. or at least the "memory" side of it

It's most likely a bad earth causing the battery to drain though

[oldcorollas]

how does bad earth cause battery to drain?

if you pull out that orange plug.. what still works? what doesn't work?

[LeeRoy]

If you still havent narrowed down what exactly is draining power just pull all fuses out and test them individually for current draw. Then refer to your wiring diagram and see what is on the circuits that are drawing current.

If these sub circuits have fuses remove them and do the same thing. Keep in mind to test the smaller circuits you will need to put the 'main' fuse back in so they can be supplied power.

Maybe your alternator is on the way out. Check voltage at idle and at 2500(?) rpm.

Hope thats of some help.

[Dale]

how does bad earth cause battery to drain?

if you pull out that orange plug.. what still works? what doesn't work?

I was always under the impression a bad earth could cause unnecessary current draw?

[LeeRoy]

Bad earths are reknowned for all sorts of weird problems yes but im not sure current draw is one of them.

[Grega]

i had a similar problem with my ae92.
it turned out that my brake light switch was sticking - only way i found it was my neighbour came over in the middle of the night to tell me my brake lights were on....
i pulled it out, cleaned it with some INOX and its never given me trouble since
hth

[toymaz]

If the car has a boot light, pull the globe and check the current draw again, it may have a switch in the lock or a normal door type switch thats not turning off.
very common problem on all types of cars

[Dimmy]

Have you checked if the alternator is charging? Should be about 14.2-14.4V when idling.

[Mos]

I have disconnected neg battery terminal, disconnected clock and then connected volt meter and get 12V reading.
<snip>
I have left the plug in and taken out all fuses from both fuseboxes and still get the 12V reading.

Where are you measuring the "12V"? These two sentences don't make a lot of sense.

If you've tried this with a brand new, fully charged battery, then something is draining your battery when everything is off (well duh ). I'm making the assumption that your alternator is working properly.

The way to determine which circuit is draining the battery is to remove one of the battery terminals and put a current meter in between the battery clamp and the battery post, set at a 10A (or higher) range.
If the current reading is something like 100mA then it's not so bad (because a battery with 20RC (reserve capacity) will take around 200 hours to discharge). The lower the better.

I'd suspect your reading will be in the amps region. You then start removing fuses one by one and see what effect it has on the current reading. You would need to check all the fuses, including circuit breakers in both kick panels inside. You can also do that with plugs on fuseboxes (as you did) but unless you know what the plug does it won't give you much information.

Try this and see what happens.

I was always under the impression a bad earth could cause unnecessary current draw?

Bad earth is an increase in resistance. Increases in resistance result in decreased current path, resulting in decreases current carrying potential, which can under no circumstance cause unnecessary current draw. It can cause the major current path to move to another area - such as another, better, ground - but the overall current capacity has decreased.

Mos.

[convert]

Thanks everyone for your suggestions.

Still haven't solved the battery going flat but have tested alternator as suggested and it is giving out about 18 Volts so will get it fixed and perhaps that will fix problem.

I disconnected clock because that was what the instructions with my multimeter said to do. And then checked voltage b/w disconnected Neg terminal on battery and lead. Manual said 4 volts or less acceptable but I got 12. Tried all the fuses out but no difference to volts or Amps (Reading was about 10 mA - thanks Mos)

Thanks again for suggestions I will get alternator fixed and take it from there.

Regards

Convert

[Mos]

Still haven't solved the battery going flat but have tested alternator as suggested and it is giving out about 18 Volts so will get it fixed and perhaps that will fix problem.

I'd suggest your battery is being cooked - check the electrolyte levels and it's likely they're quite low when the starting gets harder.

Tried all the fuses out but no difference to volts or Amps (Reading was about 10 mA - thanks Mos)

This would suggest your battery is not being drained.

Mos.