Battery drain testing

[DomP182]

I think ive got a battery drain problem, if left for a couple of weeks without being driven it will often struggle to start or worse.

So with a few days off before Christmas I've tried to test it with a fully charged (new last year) battery and my multimeter inline between negative lead and terminal but I'm getting no readout on the highest 20A setting or the mA range. I e double checked with a spare meter but same result. What's that all about?

Also to add insult my clock has gone into Back to the Future mode😫

 

[Mr Trailer Man]

Have you got the meter on the correct amps setting? Should be Amps direct current.

 

[DomP182]

Yeah amps DC, tried on the high range and low with both meters. I'm sure it must be me though, I did watch a few YouTube videos first

 

[Mr Trailer Man]

Do you have the probes in the correct comm ports on the meter?

 

[DomP182]

Do you have the probes in the correct comm ports on the meter?

 

[Mr Trailer Man]

Yeah looks right.

You're getting no reading at all?

Daft question but is the positive lead still connected on the battery

 

[DomP182]

Yeah looks right.

You're getting no reading at all?

Daft question but is the positive lead still connected on the battery

Yeah still connected, I cant have blown the fuse in both meters surely, set them both to highest settings first.

 

[DomP182]

I might just drive it more often so the battery doesnt get a chance to drain!

Not liking the hours going by by the second on the clock now, I know time seems to go by faster as you age but this takes the p!ss

 

[Mr Trailer Man]

Yeah still connected, I cant have blown the fuse in both meters surely, set them both to highest settings first.

No i can't see that being the case either

Could you test one on another car?

 

[Clio.lee]

Get a clamp meter

 

[DomP182]

That's a good shout, try it tomorrow. Could it be that the drain is lower than my meter tests and I dont have as much of a problem as I thought?

 

[Mr Trailer Man]

That's a good shout, try it tomorrow. Could it be that the drain is lower than my meter tests and I dont have as much of a problem as I thought?

There will be some drain, but it will be in the mA range. Your meter looks a decent one so it shouldn't have a problem reading the lowest of readings.

 

[DomP182]

There will be some drain, but it will be in the mA range. Your meter looks a decent one so it shouldn't have a problem reading the lowest of readings.

Yeah I didn't overly cheap out on it, about £20 rather than a £4.99 thing

 

[Mr Trailer Man]

Yeah I didn't overly cheap out on it, about £20 rather than a £4.99 thing

Don't forget to put the red probe in the mA port when testing for that range

 

[DomP182]

Tried that too then gave up in a bit of a strop, not even getting a flicker on the readings. Just cant believe two meters can be faulty, I really scratched the probes into the post and terminal too to make sure I han a clean contact.

 

[Mr Trailer Man]

Tried that too then gave up in a bit of a strop, not even getting a flicker on the readings. Just cant believe two meters can be faulty, I really scratched the probes into the post and terminal too to make sure I han a clean contact.

Not sure if it makes a difference but did you try it with the probes either way round, like black to battery and red to the lead and vice versa.

 

[DomP182]

Not sure if it makes a difference but did you try it with the probes either way round, like black to battery and red to the lead and vice versa.

Dont think I did actually, another idea for tomorrow

 

[Mr Trailer Man]

Dont think I did actually, another idea for tomorrow

Can't remember if it makes a difference, it might just be that you get a minus reading of the same number.

 

[Steven103]

Take the fuse out and use the multimeter to measure resistance. Should be a few ohms. Borrow a 5A/13A fuse from any household plug if you have to.

Assume you’ve got this covered, but current must be measured in series.

Positive terminal stays on battery. Negative terminal disconnected from battery. Multimeter “bridges” the gap between negative terminal on battery and negative on loom.

Trying to measure current in parallel (directly across the terminals like you’d measure voltage) or trying to measure current with the engine running/starting will blow the fuse.

Iirc 182s draw something like 40mA for the first 15 seconds after the doors are closed and interior lights are still on/alarm is arming, then dips to something like 10mA. Obviously equipment level & anything aftermarket could cause it to vary but the point is it should be tens, not hundreds, of mA.

 

[Steven103]

P.s fuses burn relatively slowly, I’ve permanently damaged a multimeter before by drawing more than its rated current, even though it was fused correctly. Voltage & resistance still worked but current no longer read correctly.

 

[DomP182]

Take the fuse out and use the multimeter to measure resistance. Should be a few ohms. Borrow a 5A/13A fuse from any household plug if you have to.

Assume you’ve got this covered, but current must be measured in series.

Positive terminal stays on battery. Negative terminal disconnected from battery. Multimeter “bridges” the gap between negative terminal on battery and negative on loom.

Trying to measure current in parallel (directly across the terminals like you’d measure voltage) or trying to measure current with the engine running/starting will blow the fuse.

Iirc 182s draw something like 40mA for the first 15 seconds after the doors are closed and interior lights are still on/alarm is arming, then dips to something like 10mA. Obviously equipment level & anything aftermarket could cause it to vary but the point is it should be tens, not hundreds, of mA.

The first paragraph, which fuse do you mean me to take out?

 

[Steven103]

The fuse in the multimeter. Usually just a few screws on the back for access.

 

[DomP182]

The 12A fuse had blown, dont know why as I had it set on the highest range. Ordered some new glass fuses

 

[DomP182]

I've carried out a battery drain test to try and find my problem circuit, found it quite quickly. Is this the hazard switch?

 

[Mr Trailer Man]

What the hell symbol is that 🤔

 

[Mr Trailer Man]

Is it a 20A fuse?

 

[DomP182]

Is it a 20A fuse?

Yeah 20 amp, I think it's the fuse for interior lights, radio and electric wingmirrors.

Its marked as F29 I believe

 

[DomP182]

I'll start by disconnecting the radio and autochanger see what that does

 

[Mr Trailer Man]

Yeah 20 amp, I think it's the fuse for interior lights, radio and electric wingmirrors.

Its marked as F29 I believe

Yeah I think that's the one too.

I take it the lights and radio aren't on when you lock the car?

 

[DomP182]

Yeah I think that's the one too.

I take it the lights and radio aren't on when you lock the car?

No but as the light is fading here I've noticed this, one half of the clock display is faintly lit so I'm certain it must be that

 

[DomP182]

Maybe these cut wires from a removed aftermarket head unit?

 

[Mr Trailer Man]

Has to be a wiring issue of some sort yeah.

Start with that dodgey cut out wiring.

 

[DomP182]

Dash top off again I think, I'll see how my head feels tomorrow morning. I'm getting somewhere though

 

[DomP182]

Ive had the dash top off today and found a poor connection on the clock causing the back to the future clock and semi backlighting but also the interior light had some tarnished contacts.

Once these were all cleaned up I've got the draw down to 0.063 Amps, is that within acceptable margins? It was up at around previously

 

[Mr Trailer Man]

Yeah that's fine.

63 milliamp isn't much, some modern cars will draw 150mA and that's classed as acceptable.

 

[DomP182]

Yeah that's fine.

63 milliamp isn't much, some modern cars will draw 150mA and that's classed as acceptable.

Cheers matey, I'm quite pleased I've found the source of it. Not many issue left to sort out now and they are mostly cosmetic.

Back to these cut wires, they go into an insulation wrapped loom that hangs under the glovebox so as everything else seems ok I'm assuming they are from a previous head unit and can be ignored.

Only other oddity is two wires clamped under two fuses going into the engine bay fuse box

 

[Mr Trailer Man]

Cheers matey, I'm quite pleased I've found the source of it. Not many issue left to sort out now and they are mostly cosmetic.

Back to these cut wires, they go into an insulation wrapped loom that hangs under the glovebox so as everything else seems ok I'm assuming they are from a previous head unit and can be ignored.

Only other oddity is two wires clamped under two fuses going into the engine bay fuse box

Just stick a bit of tape over the ends of those cut wires, just so they don't come into contact with anything. Should be fine.

 

[Eddie555]

Cheers matey, I'm quite pleased I've found the source of it. Not many issue left to sort out now and they are mostly cosmetic.

Back to these cut wires, they go into an insulation wrapped loom that hangs under the glovebox so as everything else seems ok I'm assuming they are from a previous head unit and can be ignored.

Only other oddity is two wires clamped under two fuses going into the engine bay fuse box

That looks like the wiring for the aftermarket alarm.. is it also bundled/taped up to the black and red pair which goes to the LED in the centre console? If so then its definitely the alarm loom and nothing to worry about.. Just stagger cut the wires neatly and tape and forget..

Sent from my SM-G977B using Tapatalk

 

[DomP182]

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That looks like the wiring for the aftermarket alarm.. is it also bundled/taped up to the black and red pair which goes to the LED in the centre console? If so then its definitely the alarm loom and nothing to worry about.. Just stagger cut the wires neatly and tape and forget..

Sent from my SM-G977B using Tapatalk

Yeah goes into the loom with the black and red alarm wires, the alarm is still working though as it woke me up at 3am the other day! All taped up now so I may just pretend I never saw it.