10/02, 17/02 and 19/02, car starts and drives fine, albeit passenger (left-hand) electric window is dead
21/02 - car unlocks from fob but power is immediately lost afterwards. No power when turning ignition.
22/02 - attempt to jumpstart using working battery from a different car, still no power.
I'm leaning towards it being an electrical or computer fault of some sort, has anyone had something like this happen before? Changing fuses alone would leave me nervous about leaving the car away from home in case there's an underlying fault that's causing them to blow.
Passenger window is likely to be accidental pressing of disable switch on r/h side of dash.
Power likely to be a poor earth. Get wd40 or similar & loosen earth connections & spray them.
Corrosion on battery posts?
Battery and terminals were changed last year.
What voltage does the battery show?
About 1.6V.
The transport plugs were removed from the battery when new.
Quote from: Paianni on February 23, 2026, 18:04About 1.6V.
The transport plugs were removed from the battery when new.
Typo? 12.6 ?
Quote from: Gaz mr-s on February 23, 2026, 18:08Typo? 12.6 ?
Nope, it was definitely around 1.6V.
Quote from: Paianni on February 23, 2026, 18:28Nope, it was definitely around 1.6V.
That battery is deep discharged and useless. Something left switched on?? The car probably won't start with that battery in place.
I don't know what warranty you had when you bought it, but one year is usually the maximum.
Quote from: Carolyn on February 23, 2026, 18:56That battery is deep discharged and useless. Something left switched on?? The car probably won't start with that battery in place.
I don't know what warranty you had when you bought it, but one year is usually the maximimum.
+1.
New battery (YBX5053) is on the way. Poor/no charging from bad terminals must have triggered sulfation last summer and it finally collapsed just now.
I had a similar problem recently where the battery would discharge over a short period of time (1 or 2 days if unused), even after installing a new battery.
I traced the problem to the car alarm. The Horn body holds 3 rechargeable batteries that no longer hold a charge and was constantly drawing power from the battery. Having removed the alarm batteries I no longer have problems with the main car battery.
Worth checking out ;)
As a side note, that would explain why the sounder is comparatively heavy for its size.
Yuasa battery on my 2 for more than the 5 year warranty that came with it.
Always disconnected when not using the car ( too often) and kept in a good state of charge.
Hopefully still going strong for the new owner.
@utterclarity Similarly a Yuasa on my diesel daily. Regularly used, but for more short trips than long these days. Charged when needed. I check it when a cold spell is forecast or unused for a while.
I suggest a battery is not unlike tyres, look after them by checking regularly and they last longer.
We regularity get 7 to 10 years out of a 12v battery in a couple vehicles that don't get driven a lot. The secret is we have battery maintenance chargers hooked up whenever that are sitting for more than a week. We use a small 750 mA Battery Tender charger on the MR2, but there are many good brands like NOCO.
Quote from: moredun on February 24, 2026, 05:56I had a similar problem recently where the battery would discharge over a short period of time (1 or 2 days if unused), even after installing a new battery.
I traced the problem to the car alarm. The Horn body holds 3 rechargeable batteries that no longer hold a charge and was constantly drawing power from the battery. Having removed the alarm batteries I no longer have problems with the main car battery.
Worth checking out ;)
Apologies if I'm hijacking this thread but this is interesting.
I take it you're referring to your MR2? Mine also has an alarm that drains the battery. Can you explain what you did in more detail please?
Quote from: fawtytoo on February 25, 2026, 22:06Apologies if I'm hijacking this thread but this is interesting.
I take it you're referring to your MR2? Mine also has an alarm that drains the battery. Can you explain what you did in more detail please?
Will get some pics together and post info later today ;D
(https://brollachan.net/images/alarm.jpg)
Stripping the alarm horn is straight forward
1) remove mounting bracket.
2) remove waterproof multi plug.
3) remove the 2 Philips screws and pull apart housing. you now have access to the rechargeable batteries.
If replacing the batteries, you will need 3
@ approx £20 each and reuse the connector to the PCB.
To date, I have just left the alarm horn off the car and everything works fine (but no siren) 8)
Quote from: moredun on February 27, 2026, 21:13To date, I have just left the alarm horn off the car and everything works fine (but no siren)
And that was enough to stop the car battery going flat? I wouldn't have even known there were batteries in there.
Different battery in mine ...
(https://i.ibb.co/dx6sywQ/PXL-20260301-190823842.jpg) (https://ibb.co/dx6sywQ)
And that was a bit clumsy of me ...
(https://i.ibb.co/XfJvqrrs/PXL-20260301-190830016.jpg) (https://ibb.co/XfJvqrrs)
Oops.
Quote from: Ardent on March 2, 2026, 07:05Oops.
Yeah, not like me to do things like that. I suppose the upside is that it was being totally removed anyway.
I Googled it. Power back up for the alarm if a thief 'stops' the 12v supply. There's a seller on ebay selling 7.2V packs, so it looks like the above is correct.
My battery pack was 3 x 1.6V giving a total of 4.8 volts compared to your 7.2 volts. Is your MR2 facelift?
Keep us posted if it works for your plz, must be lots of 20+ year old rechargeable batteries coming to end of life.
Quote from: moredun on March 2, 2026, 21:08My battery pack was 3 x 1.6V giving a total of 4.8 volts compared to your 7.2 volts. Is your MR2 facelift?
Mine is PFL.
Quote from: moredun on March 2, 2026, 21:08My battery pack was 3 x 1.6V giving a total of 4.8 volts compared to your 7.2 volts. Is your MR2 facelift?
Keep us posted if it works for your plz, must be lots of 20+ year old rechargeable batteries coming to end of life.
Looking again at your pic, you had 6 cells in 3 pairs, - so probably 7.2v
Anyone know if you can simply remove the backup battery pack and rely on the 12v for the alarm siren or will this result in the 16 beeps or alternative nagging from the car? If you remove the siren unit entirely, that could impact insurance cover.
Quote from: rusty0273 on March 3, 2026, 11:57Anyone know if you can simply remove the backup battery pack and rely on the 12v for the alarm siren or will this result in the 16 beeps or alternative nagging from the car? If you remove the siren unit entirely, that could impact insurance cover.
Read Post #24.
Quote from: Gaz mr-s on March 3, 2026, 12:30Read Post #24.
Hi. I've read the thread so understand what the purpose of the backup battery is. My question is whether it can be removed from the siren or will cause issues. moredun removed the whole siren so obviously would not hear any beeps indicating a fault.
Quote from: rusty0273 on March 3, 2026, 14:14Hi. I've read the thread so understand what the purpose of the backup battery is. My question is whether it can be removed from the siren or will cause issues. moredun removed the whole siren so obviously would not hear any beeps indicating a fault.
As it stands, although no audio from the alarm, everything seems to work ok. Remember you still have the indicators for visual feedback ie locking and unlocking the car, deadlocks etc. There are no nagging buzzers or led's to indicate a fault with the alarm.
While the siren was off the car, I broke my leg and have been unable to replace the siren without the batteries and test it. Give it a couple of more weeks and I will try it then.
Thanks and wishing you a speedy recovery.
Quote from: fawtytoo on March 1, 2026, 19:12Different battery in mine ...
(https://i.ibb.co/dx6sywQ/PXL-20260301-190823842.jpg) (https://ibb.co/dx6sywQ)
And that was a bit clumsy of me ...
(https://i.ibb.co/XfJvqrrs/PXL-20260301-190830016.jpg) (https://ibb.co/XfJvqrrs)
My battery looks like this one. Did you find a replacement? Searching seems to come up with the alternative '3x2 cell' format rather than our 6x1 versions.
Whatever the shape, it's 6 x 1.2v nicads. If there is some extra space that will allow the pack to be slightly larger, 6 cells could be bought & soldered together with an adequate iron & thin insulated wire.
There might be packs ready-made for the likes of radio controlled products. Vehicle or transmitters perhaps.
But I'd be checking first if the charging cct works, otherwise there's no point.
Thanks. I can confirm that the alarm still works fine with the rechargable battery removed or disconnected (as long as you have main 12V battery supply obviously). It looks like a 2/3 AAA format and I've had a good look on the web with no luck finding a 6 x 2/3AAA 7.2V pack ready to go.
More likely 'aa' size, although if I remember correctly they aren't named using same terms.
https://ebay.us/m/HbdHEl Need to check dimensions. - Size:84*48*18mm
Probably be ok. Is the charging cct still ok?
I'm probably just going to run mine without the backup battery but for anyone else who's looking, the pack in my car which looks the same as fawtytoo's battery, is approx 60mm x 30mm x 10mm. 6 cells in a line. There is a tray in the sounder designed to fit this size quite precisely (the tray is visible, holding the battery pack in fawtytoo's photo).
Its a GP battery, P/N GP 28AAAM6BML.
Re, the charging cct - not my bag I'm afraid - don't even know what it is, how to identify it or test it.
I've just found these which are listed under an equivalent P/N and could be a direct fit but the connector looks slightly different (ex Hong Kong).
https://www.ebay.co.uk/itm/297991409847
https://www.ebay.co.uk/itm/286572430695
Maybe somebody can take a punt and feedback.
Bit more searching - this looks right, although no dimensions listed. UK seller.
https://www.ebay.co.uk/itm/163226209115
Quote from: rusty0273 on March 6, 2026, 14:28Re, the charging cct - not my bag I'm afraid - don't even know what it is, how to identify it or test it.
Do you have a multi-meter?
Yep, I do.
Quote from: rusty0273 on March 6, 2026, 15:02Yep, I do.
The battery has two wires.. same plug connections for battery operating the siren, or the car alternator charging the batteries. So put meter across the car plug terminals & (I assume zero volts). Now start the car. If still zero volts that'd suggest it's not working. If you do see a voltage, post what it is please.
Quote from: Gaz mr-s on March 6, 2026, 17:23The battery has two wires.. same plug connections for battery operating the siren, or the car alternator charging the batteries. So put meter across the car plug terminals & (I assume zero volts). Now start the car. If still zero volts that'd suggest it's not working. If you do see a voltage, post what it is please.
The sounder is reassembled and back on my car now I'm afraid (absent one battery).
Quote from: rusty0273 on March 6, 2026, 17:44The sounder is reassembled and back on my car now I'm afraid (absent one battery).
Since you value it, do you know about moving it, for more space, but also making it much louder?
Moving it outside of the frunk? Not bothered about that as this is a weekend car, parked in my garage. Moving the sounder is a bit tricky on my car as it has air con.
Quote from: rusty0273 on March 7, 2026, 09:07Moving it outside of the frunk? Not bothered about that as this is a weekend car, parked in my garage. Moving the sounder is a bit tricky on my car as it has air con.
It can move all the way back to the bulkhead. Cut cable ties to free the loom, & cable ties to fix it. Others will have done different.
New battery was fitted 11 days ago, all seems well so far.
Thanks for the advice.