I'm currently trying to identiify what appears to be a parasitic drain. I've checked for amp changes when removing fuses in the engine compartment fuse box. Now I'm trying to do the same for the fuse box inside the car. These fuses are only accessible with the front door open - but, with the front door open, circuits (internal lights) are triggered. Simple question (but tricky answer?) - how do I disable the circuit(s) that are triggered when the door is open? In (very) old cars this would be a simple push button gadget but there is nothing at all obvious in or around the door. I can only assume that its built into the door locking system somehow. Can anyone assist please?

I'm fairly sure that you can close the latch mechanism with a screwdriver so that it thinks the door is closed.

OK. Thanks. I did think that might be an option bujt didnt want to fiddle about and, potentially, end up doing something that was irretrievable.

Yep, that screwdriver technique is what to do. You may need to wait half an hour after flicking the latch over for things to shut down properly though.

 

If you get odd results from fuse removals, try this instead: 

Apparently the link in the OP is now not working but scroll down the thread to the bottom.

Edited 14 January, 20215 yr by Wino

Thanks Wino. I tried the screwdriver trick and it certainly helped - but didnt seem to affect the circuit that feeds the light that shines down from the wingmirror. I did wait a while after the light went out but I think it was still taking power along that circuit. However, having seen your reply, I'm now inclined to think I was a little impatient. I will try again but, this time, give it a good 40 minutes before I make a judgement. Thanks for the link - I've downloaded it and will read through it while (hopefully) the Octavia is settling down (electronically) to a testing state.

That millivolts technique does require the fuses to be the type with exposed metal pads on the accessible side. (Can always swap some of that type in for the positions of interest).

 

 The interior lighting circuit stays 'primed for action' for about 30 minutes typically after the lights go off. The coil of the relay that powers the lights stays energised after the lights themselves are extinguished by letting their ground connection float high.  "Terminal 30g" is worth googling if you're interested.

I probably need to start a new thread on this but, as you have been so helpful (and clearly a bit of an expert on these things), I thought I'd update on here.

 

I left the car to settle completely and then went back to do some testing. The reading on the multimeter was 0.03 (on the max 10 amp) setting,  which I assume equates to 30mA - which, I believe, is about right and as it should be. Took out all fuses one by one from internal "fusebox" and the only differences were that the  reading dropped from 0.03 to 0.02 when I took the fuse for "Front Power Window" out and from 0.03 to 0.00 when I took out the fuse for the "Anti-theft alarm system". I assume that the drop from 0.03 to 0.00 for the Alarm is as it should be (The Alarm has to take some power). The "Front Power Window" drop was interesting........but...........

 

1. If I'm only getting 0.03 on my multimeter then there IS NO parasitic drain on the battery? If battery loses charge after 5 days standing in garage then maybe its the battery that's faulty (bought last May)

2. Yesterday I was testing drain in relation to fuses in the engine compartment. Initially the multimeter was showing over 1 amp. Dropped significantly when I took radio fuse out (down to about 0.29 amps). I put fuses in and out and, eventually, I was getting reading of 0.03. I thought I had solved something but now I'm thinking that all those changes were more to do with the Octavia gradually shutting down? Or did I do something inadvertantly (changed a dodgy fuse connection?) that solved the parasitic drain?

 

Would welcome any thoughts on the above.......but quite understand if they are totally ignored. I'm afraid I'm far from being any sort of a car mechanic...more an enthusiastic amateur!

1. 30mA is borderline/inconclusive I'd say; certainly nothing majorly wrong at that level.  If the battery is in a good state of charge when the car is parked up, that shouldn't cause it any grief after 5 days, if that is the consistent level of quiescent current. 

 

Have you measured battery voltage before and after starting the engine? These two simple measurements, done in that order, can tell you a fair bit about the battery's state of charge and the alternator function.  

 

What type of journeys is the car being used for? (Duration/miles and frequency)

Edited 14 January, 20215 yr by Wino
sp

Thanks for replying and taking an interest. I was getting same problem with previous battery which my garage tested and said was OK.  It was a very old battery (original?) but they said sometimes they pass a test but aren't 100%. Anyway, rightly or wrongly, I decided to buy a new one (last May). Seem to be getting same problem. First encountered the problem late April last year - after car had been standing unused for a few weeks (due to covid lockdown). Since then, and since new battery, it hasn't been used much. 2 or 3 times a week but only used for about 6 miles each time. I have since had it in my carport where I can  fully charge the battery. I leave it unused but after 5 or 6 days when I try it again it's gone flat. Does any of that point to another, different issue? I know it's not used a lot but surely a fully charged battery should be OK after just 5 or 6 days?

(I'll try the voltage test tomorrow hopefully)

1 minute ago, Wingreen said:

I know it's not used a lot but surely a fully charged battery should be OK after just 5 or 6 days?

Yep.

Bear in mind though that whenever a lead-acid battery gets down to a very low charge state it accrues damage that may not be fully reversible.

 

Make sure the alternator is doing a good job first, then do  some more parasitic drain checks, to try to build up a picture of the typical situation. The milliVolt testing across fuses in-situ has the significant advantage of not disturbing the network of control modules.

OK.  Thanks for that. It's possible that this lockdown has led to both old and replacement  batteries getting some damage. (Would such 'damage' show up if I took it to my garage and ask them to test?).

Anyway, you have given me some things to try:

1. Check alternator (although if it's losing charge from full in just 6 days standing unused, I'm guessing it can't be that)

2. Check voltage of battery before and after starting.

3. Change fuses for more accessible type and check for drain again.

 

At least with ongoing lockdown it'll give me something to do!

 

Really  appreciate your help.

Just thought......2 easy things to try?

 

1. Remove the Alarm fuse (amps dropped from 0.03 to 0.00 when removed). Assuming don't need that fuse in order to start car. If battery still goes flat must be battery problem.

2. Remove front window fuse (amps dropped from 0.03 to 0.02 when removed). Should be acceptable amps so, if battery still goes flat, likely to be battery problem.

 

Unless I missed something.

 

An update:

I fully charged the battery late afternoon on 14th January. It has sat doing nothing in my car port since then. I checked voltage across battery this morning (20th January - five and half days later) and got a reading of 25v (Its marked as a 12v battery, 52Ah). I tried starting the car - eureka! It started fine. The voltage reading across the battery while idling was 30v. I assume those numbers indicate everything seems OK? 

 

I wonder whether its possible that, when I was fiddling and checking fuses for battery drain, I did something that somehow fixed whatever was draining the battery (if anything). Maybe a loose connection or something?

 

Anyway, I'm going to leave it a few more days, sitting in car port and see if it starts again - basically see how things go. I'm still torn between it being a battery drain (although 30mA shouldnt be too unusual and a 52Ah battery should last over 70 days if its only using 30mA) OR maybe a faulty battery - or at least one that would be fine when things were "normal" but cant cope with all the non-use of a car when we are in lockdown).

 

Any thoughts would be most welcome.

There's something very wrong with your voltage readings.

Meter or operator, dunno which; try a new battery in the meter if it isn't recent.

Ummmm.....operator error! (I told you I was an amateur - enthusiastic though).

 

Looks like I had it set on AC (Duh!). I then set multimeter correctly and it registered 11.84v before starting. I then started the engine (only just - it was struggling to start) and the reading was around 14.1v when idling. Not sure - but that 11.84v doesnt look good.

 

If I fully charge battery and then disconnect it - would it help me find out if it was a battery problem? (If voltage drops then battery faulty?).

 

I still cant understand why, if battery is OK (rated 52Ah) and fully charged and my multimeter is only taking 30mA (and car isnt being used), why I'm getting a problem after only a few days.

 

(Going back to an earlier post - would make any sense for me to take the "Front Power Window" fuse out and see how things go - "drain" fell from 30mA to 2omA when that was removed)

46 minutes ago, Wingreen said:

If I fully charge battery and then disconnect it - would it help me find out if it was a battery problem? (If voltage drops then battery faulty?).

 

I think this is a good idea, yes. It will localise the problem to either the battery or a parasitic drain.

Once it's clear whether or not the battery can hold a charge on its own, it'll be easier to find out what else may be going on.

 

What I'd do is disconnect the battery from the car, just the earth lead will do, then put the charger on the battery for as long as it says it's doing something. Then disconnect the charger and wait a couple of hours. Now measure battery voltage (which should hopefully be around 12.6, but a little temperature dependent so note the ambient temperature during the measurement. If it gets nowhere near this voltage try applying the charger again, patience may be rewarded on this.  You cna reverse some battery degradation with persistent charging.

 

Wait a day or two and remeasure, or check it once a day over a few days. Anything to see if it's staying 'up' when not connected to the car. 

 

14.1 is a little lower than optimal for charging from the alternator, so it may be worth cleaning up some earth connections while the battery negative is disconnected.  Main engine to chassis one, both ends of, would be my first choice.

 

 

Thank you so much. I will do as you suggest. Watch this space!

(Interim?) Update. Below are readings taken so far:

 

20th January: Topped up battery. Fully topped by 12 noon.

14.00: 12.38v (forgot to take temp)

17.00: 12.40v (7.2 deg C)

22.00: 12.34v (5.5 deg C)

21 January:

09.00: 12.32v (4.4 deg C)

22 January:

11.00: 12.30v (5.3 deg C)

23 January:

09.30: 12.24v (3.0 deg C)

24 January:

09.00: 12.23v (3.2 deg C)

12.00: 12.29v (3.8 deg C)

 

Doesnt look to me as if its a battery issue. I'm happy to keep monitoring (I have a 2nd car I can use for getting about) but looks more like a parasitic drain? Having said that, multimeter monitoring was only showing 30mA (on a 52Ah battery). Removal of fuses only let to a change when "Front Power Window" fuse removed (dropped from 30mA to 20mA) and when "Anti-theft alarm system fuse removed (from 30mA to 0mA).   Could it be an intermittent drain (which would be very hard to identify).

Would a useful (next) step be to reconnect everything and check battery voltage every day and see how/if it changes. If it drops then the combined information/tests may well mean the (nightmare scenario) intermittent parasitic drain!

 

 

41 minutes ago, Wingreen said:

Could it be an intermittent drain (which would be very hard to identify).

Would a useful (next) step be to reconnect everything and check battery voltage every day and see how/if it changes.

Maybe soon but...

Your battery charging didn't result in a very full battery, as judged by the 12.4ish volts.  It should be more like 12.6/12.7 when fully charged. I would've persisted more with the charging and put the charger back on it the next day to see if that brought it up more.

OK. Thanks.....again. Best case scenario is that its a battery problem. I bought it May 2020 but maybe it was a bit of a dud? (Got away with it over the summer when using car a couple times a week but the under-use during lockdown is showing up its shortcomings?)

 

Anyway,  I will charge it again tomorrow - and check voltage again. I will charge it every day for a 6 or 7 hours for a few days - and see if it gets to a higher voltage condition.

 

Update:

 

I took the approach you suggested. So far this what I have found/recorded

 

Day1: Charged for 6 hours. V after charge: 12.87. (Temp 4.3).

Day 2: Voltage after overnight "rest" of 17.5 hours: 12.38 (Temp 2.5). Then charged for 5.5hrs. V immediately after charge: 13.06 (Temp 5.9)

Day 3: Voltage after overnight "rest" of 18.5 hours: 12.59 (Temp 5.1). Then charged for 8.5 hrs. V immediately after charge 13.23 (Temp 8.3). Voltage after 2 hr rest (to settle battery) 12.85 (Temp 8.7)

Day 4: (Today): Voltage after overnight "rest" of 15hrs: 12.77 (Temp 8.6).............

 

Not sure if any othat helps. I will keep doing it every day. (I only realised on Day 3 that a batter ideally needs to rest for couple of hours - you had told me - before it demonstrates its true "state"

Looking healthier. 

Maybe try not charging it for a few days and just measure voltage to see if it holds at a good level?

OK. Thanks. Will do. So........battery looks OK, in terms of taking a charge. After charging today I willleave for 2 hours and take a voltage reading. Then leave it alone for a few days.

Two questions:

 

1. Should I leave the neutral connection off? (Presumably yes, as it will be a check on the battery itself, with nothing to do with the car).

2. Any harm/benfit in taking voltage readings say, twice a day, while the battery is just sitting there, resting?

 

1 yes

2 no harm at all

Results (battery fully charged, Neutral disconnected) with dates and times and temp:

28 Jan: 10.00, 9.9 deg C: 12.84v

28 Jan: 15.00, 10.3 deg C: 12.87v

29 Jan: 9.30. 8.9 deg C: 12.79v

29 Jan: 11.30, 9.0 deg C: 12.8v

30 Jan: 9.30, 5.7 deg C: 12.77v

30 Jan: 11.30, 5.4 deg C: 12.79v

30 Jan: 18.00, 4.9 deg C: 13.17v (big jump for some reason)

31 Jan: 9.30, 4.2 deg C: 12.74v

31 Jan: 16.30, 5.1 deg C: 12.78v

1 Feb: 9.30, 3.7 deg C: 12.82v

 

All in all, I suppose these suggest that the battery is OK? Maybe I didnt charge it up properly/fully earlier in the process when it was connected to the car and if I connect it all back up and monitor voltage (while not using car) it might tell me something new?

 

Any thoughts on "next steps" would be much appreciated.