Parasitic current draw 1988 12HT 24v (1 Viewer)

[metro55]

Hi Guys,
I have read multiple posts regarding what appears to be a common problem with 24v 60's having flat batteries, some intermittent.
I have put up with this for 23 years and have decided to try and solve it.
I have had a relay in place for all that time that I simply toggle off when parking.
I have just installed a winch and decided to use a relay and toggle in the cab to activate the power to the winch.
(will add a soft alarm later to sound when winch activated so I remember to switch it off again.)

The car isolator battery cable on the ground side of the relay bolts to the body of the car and then a cable joins that to the engine.

Whilst setting this up in a new cradle I used my multi-meter to test and found a strange situation:
With the relay in the "OFF" position ,(so no earth to ground from the battery (open circuit) I get a reading of 24.5 volts.
So the body is now positively charged.

If I start the car and re- test straight after turning the car off and switching off the power to the relay I get a reading of "ZERO VOLTS"
Wait 10 minutes and re-test I get a reading of 24.5 Volts.
I have disconnected: lead to alternator ; Electric window actuators and intake pre-heat element & the problem persists.
Please throw some ideas at me I'm stumped.
metro

 

[OSS]

Get rid of the relays - or at least replace them

 

[duncanrm]

Digital Multimeters are "high impedance" and as such can be really misleading in an automotive environment.. it might read 24.5V but that doesnt mean you have a "usable" 24.5V supply.. put a load on it (like a Test Lamp) to verify that you really do have a viable source of usable voltage, or use the current measuring capabilities of your meter to measure actual current flow.

A few points:

• Your best friend when diagnosing simple electrical faults on old Landcruisers is a Test Lamp with an incandescent globe. They are superb for:
  • verifying you have an earth
  • verifying that you have 12/24V+
  • Checking fuses
• Digital meters are great for:
  • Measuring an exact voltage (such as when looking for charging voltages)
  • Measuring current under 10A
  • Measuring voltage drop in a circuit
• When diagnosing a parasitic current draw you need to measure actual current flowing out of your battery using the DC Amps setting on your meter and inserting your meter in series with your battery.

Sorry for the vague advice.. its worth doing a really deep dive on some of this on the internet - the older your Landcruiser and the more accessorized it is the more you need to understand it.

 

[metro55]

Thanks for the replies,
There is nothing wrong with the relay's the one for the winch is brand new & I believe better than an isolation switch under the bonnet.
D/heads here love to prank those with exposed isolation switches and unwind cables when you leave ya car parked.
The older relay has saved many many batteries.
Until that was installed I fried more batteries that I can remember.

I do remember 2 of them actually reversed polarity, Yep -VE became +VE
@duncanrm Thanks for the advice (not vague at all), I followed through this morning

I'm not impressed with the cheap import shunt the pic shows it displaying 14v but it was actually 21.7 on the first pic I took & does not show draw.
So, test lamp was bright enough that I'll put it on the Xmas tree for the grandkids this year.

I have never tested current draw with a meter before. I'm guessing .14 amps is not a lot but enough to flatten a battery.

One quirk I did notice, if I disconnect the +Ve battery lead (so no power to the car ) then replace it the 24v short still exists
To make the short disappear I need to start the car, which I believe reverses the polarity of what ever is draining the battery when it's off
then given a few minutes after turning off the car the short returns.

I'll go back and check to the central locking and disconnect it and re-test.

 

[metro55]

Dumb noob with the shunt, wired correctly give better results.

 

[metro55]

Getting closer,
any advice appreciated regarding the large white wire on the POS battery post of a 24v HJ61
I removed every fuse and tested, fault exists with all fuses removed.

 

[duncanrm]

Possibly to the Glow Screen on the intake manifold?

 

[metro55]

Thanks duncanrm,
disconnected all wires to the screen, problem persists.
I'll start removing all non standard wiring, immobiliser, turbo timer 24v relays (and 12v converter) for trailer plug to be 12v etc

The last resort will be an auto sparky. So far unable to find one that's not related to a bushranger.
The last time I got a mobile sparky he spent two hours and could not solved the problem & then charge me $250

Two days later I convince the local car audio shop to send his guy over when he knocks off work
with the promise of cash .....he fixes the issue in 5 mins and said $50 will do

PS:
Just took a look at your building the princess page, "WHAT A TRANSFORMATION" amazing what 80lbs will do
not sure I could sacrifice the drink, good job
metro

 

[duncanrm]

PS:
Just took a look at your building the princess page, "WHAT A TRANSFORMATION" amazing what 80lbs will do
not sure I could sacrifice the drink, good job
metro

Thanks

Good luck with the resolution of your fault.. I am not sure whats going on. The more you educate yourself on automotive electrics and diagnosis, use of a meter, test lamp etc the sooner you'll sort this out. Its difficult from a distance. A parastic draw of .14A is not low, but its not even close to enough draw to require a battery to be disconnected overnight.. it'd take 10 days++ to make any appreciable impact on a decent battery.