Burntweenie

Burntweenie

Member
This one's a real puzzle, hoping that someone might have a bright idea - here we go:

I have a slow voltage leak to earth. I've done the following to try an isolate it, with zero results:

Voltmeter between earth strap and negative terminal, removed all fuses and fuseable links in turn - still reading 12v.
The same, with voltmeter between live strap and live terminal - 12v.
Removed live strap from starter solenoid - still reading 12v.
Removed each of the other two live straps in turn - still reading 12v.
Removed all three together - reading 0v.
Removed engine end of earth strap - still reading 12v.

Starter solenoid strap continuity reads OK.

No modifications as far as I can see...(famous last words).

I recently refurbished the starter solenoid, but the issue pre-dates it.

Any ideas? Or is it time to seek an automotive electrician?

Many thanks in advance for any help. Cheers!
 
I think you mean you have a current leak. As in the battery going flat in say 2 days if it's left unused. If so then you need to measure current, not voltage. Most multimeter's will only go up to 10amps current. You can buy a device which replaces the small car fuse. Pull out the fuse and plug it in to the fuse socket and it then tells you the current flow through that fuse socket. Most are 10 amps rated only but I found a cheap one which will measure up to 20 amps.
 
How much are you talking in mA? The FL1 generally has a constant 100mA drain on the battery, slightly more on some, depending on options fitted. This is to keep the alarm active and other permanently live units like the clock, radio memory and so on.

If it's a lot (more than 200mA) then it could be worth disconnecting the alternator to see what effect that has on the current drain.
 
Burntweenie said:
Voltmeter between earth strap and negative terminal, removed all fuses and fuseable links in turn - still reading 12v.
Some confusion here - earth and -ve should be equipotential, ie 0V
The same, with voltmeter between live strap and live terminal - 12v.
Same here
Removed live strap from starter solenoid - still reading 12v.
Removed each of the other two live straps in turn - still reading 12v.
Removed all three together - reading 0v.
Removed engine end of earth strap - still reading 12v
Click to expand...

As Nodge says, you mean current leakage. AKA parasitic draw. Switch off the interior light, drop the rear window right down, note your radio code, then set up your meter to measure current, ie put it between batt neg cable and neg terminal.

Measure the resting current draw. If over about 100mA then pull fuses until it drops down - you have found your faulty circuit. If the car has just been shut off, it may draw a little more than usual before going dormant.

Let us know how you get on.
 
Hippo said:
My v6 took 24mA when locked with the alarm on.
Click to expand...

My V6 was about 25mA too. My current TD4 SE is just over 100mA when first switched off, dropping 95mA after 10 minutes or so. I have more things too keep the draw higher than a V6 FL1.
 
Had a free hour today so had a play - read around 20ma. Removing fuses in turn didn't change the reading.

Before I did this, I discovered the purple and white cables to the HDC switch in the gear lever had been torn off, and were flapping around with bare wires exposed. Soldered them back onto the switch, and the green HDC light now shows when engaged (it never did before). Could this have been the source of the current drain i.e. if the wires touch earth? Fingers crossed.

I also discovered a 12v live running to the after-market tow bar, with all the electrical gubbins tucked inside the o/s rear boot trim. Not the neatest job.

As an aside, my rear window drops itself completely when the battery is disconnected. Is this supposed to happen?!? I found the above whilst checking the earth point for the window and rear demist (which doesn't work).

Bloody car electrics...
 
correct me if I am wrong but you should have a 12v feed going to your tow bar this is to charge the extra battery in you caravan ect.
 
Burntweenie said:
As an aside, my rear window drops itself completely when the battery is disconnected. Is this supposed to happen?!? I found the above whilst checking the earth point for the window and rear demist (which doesn't work).
Bloody car electrics...
Click to expand...

Yes the back window drops if you disconnect the battery. Its so it can recalibrate when you put it back up
 
Quick update - a few days on and she's holding charge. Also located the issue with the re-demist: the positive spade terminal had snapped off from the glass. Luckily there was enough still attached to crudely re-fix the live to the terminal using a single choc-bloc connector (soldering iron couldn't get it hot enough).
 
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