battery drain on ignition system?

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jigarai
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battery drain on ignition system?

Post by jigarai »

Hi folks,

I've got an issues with my cranking battery as follows:

It is quickly flat when I leave the keys in with the ignition on - quickly as in a minute or two - (courtesy lights switched off!)

A voltmeter gives the following readings between the terminals:

Ignition off: 12.6 v and steady - (holds this for days between)
Ignition on: 11.7 v and falling fast. A minute or two is enough to drain the battery to the point I need a booster to start the engine. 
Engine running: levels out at 14 v fairly quickly

I have pulled all the fuses one by one and none have made any difference to the drain. 

So - before I fork out on a new battery, any suggestions as to potential underlying issues?

I tested the resistances on the (green label) coil the other day and the primary circuit was a little high: 1.1 Ohms (spec 0.5 to 0.8 according to Baxter's post on Brickwerks...). Could that be it? Sorry if naive-

The battery has worked hard this winter as I've had separate(?) cold starting issues meaning it's had to crank and crank to get the engine going on the colder mornings. I'm aware on that basis it could simply be knackered but thought I'd check for any other known issues or thinks I can look at. 

TIA - JB
1985 Caravelle. 16v GTi. 4 speed, manual. LHD (US import)

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Mocki
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Re: battery drain on ignition system?

Post by Mocki »

Carb inlet manifold heater stuck on ?
Not fused , the big red (Normally appears to be pink with age) in the engine bay on the top of the engine controlled by the relay in the black box in the LHF of engine bay .
Steve
tel / txt O7947-137911
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jigarai
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Re: battery drain on ignition system?

Post by jigarai »

Thanks Steve- I wondered about that. I’ll have a search on here for how to test it but any guidance will be gratefully received!
1985 Caravelle. 16v GTi. 4 speed, manual. LHD (US import)

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Mocki
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Re: battery drain on ignition system?

Post by Mocki »

Easiest way to rule it out is to simply unplug the thick red wire going under the carb to the inlet manifold heater
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Steve
tel / txt O7947-137911
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jigarai
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Re: battery drain on ignition system?

Post by jigarai »

Nice one- I realised last night- then check for the drain on the battery. Of course! I’ll le you know how I get on. :-)
1985 Caravelle. 16v GTi. 4 speed, manual. LHD (US import)

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jigarai
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Re: battery drain on ignition system?

Post by jigarai »

So, having pulled the connection for the manifold heater the battery voltage stabilises. 👍 . I’ve located the relay and traced the connections- a power in from somewhere. A purple one that comes from the coolant system and two brown wires (earths I’m guessing). So what is the next step… I could take out the relay and test it?
1985 Caravelle. 16v GTi. 4 speed, manual. LHD (US import)

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jigarai
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Re: battery drain on ignition system?

Post by jigarai »

Looking on Brickwerks I’ve ordered a replacement relay. Makes sense to replace it anyway I reckon. Eliminate that from the equation.

Also found this thread on here for same issue- https://club8090.co.uk/forum/viewtopic.php?f=60&t=80610
1985 Caravelle. 16v GTi. 4 speed, manual. LHD (US import)

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jigarai
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Re: battery drain on ignition system?

Post by jigarai »

Okay, so manifold preheater relay is replaced and I’ve checked the resistance between the power supply to the hedgehog and an earth and it’s 0 ohms. From what I’ve been reading that’s maybe okay when it’s cold but it should heat up quickly and then the power draw drops as the temperature rises… is that correct?

Currently situation remains that if I leave the ignition on without starting the engine the battery will be sufficiently drained that it won’t crank the engine within a minute or two.
1985 Caravelle. 16v GTi. 4 speed, manual. LHD (US import)

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Mocki
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Re: battery drain on ignition system?

Post by Mocki »

So have you established that the switch is not constantly on , and that power is not flowing when the ignition is off ?
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cobblers
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Re: battery drain on ignition system?

Post by cobblers »

If your battery is healthy, nothing on your van (other than the starter motor) is able to flatten it in the space of minutes - At least get it checked, but realistically, it needs to be replaced.

It's usually a 80-100AH battery, so for it to be genuinely flattened in minutes, you'd need something to draw in the region of 800-1000 amps!
This would cause incredible amounts of heating of the battery, the terminals, wiring etc, not to mention whatever component was drawing the current would be probably on fire by now.

The carb heater does draw a fair amount of current, by design. Perfectly enough to take the charge out of a worn out battery. 
If the 10-15A draw of the carb heater is enough to sag the battery voltage to 11.7 quickly, again this suggest that it's very unhealthy.
 

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Re: battery drain on ignition system?

Post by TONYT25T25 »

I had a suspected bad battery on another vehicle. Drove the car to Halfords for free battery check. When he attached his device to the battery said put the lights on and start the engine, nothing happened this process drained the battery. So new battery nneeded was conclusion.
1984 Campervan 1.9DG Petrol WBX

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jigarai
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Re: battery drain on ignition system?

Post by jigarai »

Thanks all- I’ve been reaching the conclusion that this was the battery’s death throes as it has deteriorated further. Moki, I have confirmed that there is no draw from the hedgehog when the ignition is off.

Will get the battery tested and if necessary replaces this week and update here if any issues still persist.

Thanks as always for all your support. <heart> club80-90
1985 Caravelle. 16v GTi. 4 speed, manual. LHD (US import)

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Re: battery drain on ignition system? 2.1dj

Post by spanishfly »

Hi, presumably there is some parasitic draw testing going on?

I may have one too and having removed the -ve and connected my ammeter in series I seem to have 150mA no matter what despite having removed all the fuses one at a time nothing changes?

I did wonder if I was mis reading the display but on milliamps it shows as OL on Amps 150. 

What would the forum take to be a normal level of draw please? 
 
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cobblers
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Re: battery drain on ignition system?

Post by cobblers »

On a standard t25 there is almost zero draw with the ignition off, the only thing that maintains power is the clock and this would be 5-10mA.
Additional stuff such as alarms, stereos etc need a permanent feed and often they aren't wired through the OE fuse box and will (hopefully) have their own fuses, unfortunately these fuses are probably buried under yards and yards of sticky electrical tape on the side of a big awful bulge in a wiring loom somewhere.

150mA is quite a bit more than I'd expect on a T25 but it's about par for the course for most modern vehicles. 

spanishfly
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Re: battery drain on ignition system?

Post by spanishfly »

Thanks and apologies if I'm hijacking this thread! Kind of related.

Having ruled out all the fuses I can find moved to the alternator which is giving out 13.5v at the battery (I replaced the earth strap at the battery after scratching off paint at the mounting point under the seat and now have 13.7v at the battery), 13.78v at the engine earth strap and 13.79v at the alternator (wbx 2.1 dj so 90A? label has fallen off!)

So 0.01v lost between alternator and chassis..... seems ok, or seems to good to be true better check that?

0.19v lost between alternator and battery 5m..... away seems ok?

Still have 153mA drain??

 I removed the bigger double wire from the back of the alternator that didn't help so I guess it rules out diode(s) in the alternator as a possible cause? Also removed stereo fuse not that.... 
 
1987 Westy Joker 1.6TD
1987 Dehler Profi 2+2
1988 Syncro RHD panel
 

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