27 replies to this topic

[Detta]

Can anybody tell me how many amps a VXT should draw when turned off? I presume that this would only be whatever is required to keep the alarm alive? Basically I'm hoping to find out how many Amps I should be seeing if, with the engine an electronics off, I disconnect a battery terminal and measure current in-line between the battery and the terminal.
 

 

Please bare in mind that I'm a total novice with electronics, but I'm hoping to use my limited knowledge, and a methodical approach to diagnose, and hopefully solve a real PITA of an issue - Batteries are rapidly discharging themselves overnight, to the point where the next morning it's a laboured start, and if I don't drive the car for any more than a day or two, it's a total flat. With the advice of some members here, I had to break in last night because it couldn't work the central locking, and the secret button did nothing! At first I thought that the issue was it was battery related, but have recently gone though two halfords advanced batteries (who confirmed they were FUBAR via some testing kit, but where unable to tell me exactly what it was testing for beyond voltage), I've come to the conclusion that it must be a short, or parasitic draw somewhere that's causing the discharge, and in turn, slowly killing the batteries? The confusing thing is that no fuses have blown, so I presume that whatever is causing the issue isn't as dramatic as it could be.

So my current plan is to find out what it IS drawing vs what it should be, and if this figure is higher than normal, pulling fuses one at a time to see if and when this figure normalises? This should at the very least give me an area to start looking no?

It's a bit concerning, because this issue has only revealed itself since a semi-recent trip to a local garage where they managed to flatten the battery, and kill the immobiliser (it needed reprogramming, not replacing) while working around the ECU and LOOM of DOOM, so I do wonder if it's related, and the thought of a short being 'somewhere' on the LoD is a scary one indeed!



So, in summery: How many AMPS should a resting VXT draw?
 

Beyond that I would welcome any additional informed advice or pointers.    
 

[Detta]

I should also mention that the alternator IS working, we jumped it, and brought the battery back to life with a 45 min drive, it's providing a healthy amount of juice. However, I do understand that there may be a shorted diode within the alternator that could cause this issue?

[techieboy]

Replace the central locking backup battery or dump that entire circuit altogether and you'll probably solve the problem.

[slindborg]

Not really seena  loom of doom fault on the VXT, possibly because the ECU has a more tollerant input stage compared to the N/A ecu, BUT thats not to say you arent the first

 

Once a car is asleep (shouldnt take long for a VX) then you should be looking at something in the region of 100-300mA dependig on the Alarm and what the LED uses to flash.

 

[Detta]

Ok well it's sitting outside to sleep, but on a fresh multimeter connect, it's reading at around 0.3 Amps (just under), a google search, based on other cars suggest that:

[color=#696969;][font="arial, helvetica, sans-serif;"]'Just fyi, typical drain key off (and the vehicle must sit for 30-45 minutes to ensure all modules go to sleep as well! ) is to be under 0.05 amps, or 50 milliamps.' [/color][/font]
 

&

[color=#696969;][font="arial, helvetica, sans-serif;"]'[/color]0.10 amps will kill your battery quick like, you should get it down as close to 0.00 amps as possible. My experience was that to keep the radio stations, etc. it takes about 0.01 amp on the meter. So yeah, you got something going on... In my case, it was the key lock light staying on and the door lights (or rather door light relays) staying on.'[/font]

 

 

Would you educated folks consider these statements misinformed?

If Slind is correct, then this reading is towards the upper end of what would be considered acceptable? 

Edited by Detta, 03 March 2015 - 11:56 AM.

[techieboy]

No. It's an order of magnitude too high.

 

Like I said, replace the central locking backup battery or disable that entire circuit and then see what the quiescent drain is.

[Detta]

By the central locking backup battery, you mean the little bike battery in the boot (for secret switch)? If so, I thought I remember reading here that this shouldn't be pulling (to charge itself) with the ignition off? I presume that I could just yank a terminal to test this? In doing so, everything else should function as intended?

[slindborg]

You'd want to pull the relay and the battery wires, incase the relay is naffed too.

 

ime the closer to zero the better, but I've also seen cars "acceptably" sleeping at 300mA.... yes its high but depending on the tech in the car it can be normal.

 

[Detta]

Yanked the backup battery terminal, and was down to 0.015 vaults! 

 

But this was with my stereo (still) disconnected, after reconnecting: 0.03, I presume that this is a nice safe figure to be arriving at? It is as techie said, an order of magnitude lower!    Thank you all.    Does anybody happy to know the battery size that needs replacing? Would you advise that I do so, or am I just setting it up to fail again?

[Detta]

And is it the relay that controls whether or not it's trying to charge itself with the ignition is on? Because if so, surely this would have to be stuck to allow this problem to have happened in the first place? Sorry to ask so many questions, but is anybody able to tell me which relay would control this? And whether or not it's sole purpose to control this battery backup, or does it's potential failure have other implications? 

Edited by Detta, 03 March 2015 - 01:10 PM.

[slindborg]

I think phjohn or similar user name wrote a guide on replacing the backup battery

[Detta]

For anybody else having similar issues: http://www.vx220.org...backup-battery/

[Gorbachov]

Mine has an issue with the 12v socket. Didn't have a fuse in it when I got the car. Put one in socket works fine however will kill the battery overnight. Mine was drawing over 1 amp with ignition off. Pull the fuse and it drops to 300mA. So I'd say its acceptable too......

[Detta]

300mA was definitely causing me problems after a night or two of not using it, after disconnecting the battery backup it's now sitting at 30mA, so I would suggest that you try the same thing Gorbachov. I'm not however going to replace the backup battery until I can establish where the potentially faulty cut-off relay is (not mentioned in the guide), as without this I presume it would be a useless lump anyway. So I would still welcome any advice on this particular issue! 

[Zoobeef]

If i remember right then the backup battery is permanently connected to the main battery but has a diode in the line to stop the main battery draining the backup.

ill have a quick look when i get chance.

[Detta]

Thanks Zoo, so in theory, this would prevent the main battery from draining the backup, but it wouldn't prevent the backup from draining the main battery if and when the backup failed (as per my example)?

Edited by Detta, 03 March 2015 - 02:07 PM.

[christhegasman]

Thanks Zoo, so in theory, this would prevent the main battery from draining the backup, but it wouldn't prevent the backup from draining the main battery if and when the backup failed (as per my example)?

Not familiar with turdo locking but that sound like what zoobeef is saying it is possible your knackered locking backup circuit is pulling power from the main battery constantly

Edited by christhegasman, 03 March 2015 - 02:20 PM.

[Zoobeef]

Yeah thats right. Worth sticking a new battery in but also checking the Diode is in good nick too as most people only find the backup battery is tits when the locking doesnt work after the main one goes flat.

 

Just dont get a new one from Vauxhall :/

[Judderman]

anyone have a link to the best place to pickup a replacement backup battery [color=rgb(84,84,84);font-family:arial, sans-serif;font-size:small;]YT4L BS [/color]

[Gorbachov]

Hmmm seems strange that mine is no longer killing battery's, was a while back that I was looking at it so might have been 30mA definitely dropped with the fuse pulled though. Haven't been bothered to sort it yet as I never use the socket anyway.