Battery Drain

Kernowchristoff · 15th December 2019, 15:20

Hey Guys

After having a terrible time with an electrical issue a month ago with a certain high street auto repair shop ive now got the same problem.

Last week came home left my tourer for a day, Came out turned the key and again flat battery. The message centre gave me no indication of a voltage drop. A mobile mechanic out since the car is stuck in the garage. The Alternator was charging when he jumped her. However after £60 his diagnostic was too new for the car.

Later on about 8pm went out the battery was flat. Ive had a new battery fitted although it is a halfords one. My mind is saying alternator after almost 18 years and 216,000 miles maybe a replacement.

Thoughts please i am tearing my hair out i dont want to scrap her.Way to good for that.

Mike Noc · 15th December 2019, 15:33

Chris always helpful to know the engine type on faults like this - if you add it under the description saves people having to look it up.

First thing is to eliminate the battery so charge it up fully on the bench and leave it overnight then fit it and see if it has lost any power whilst resting.

If the battery is OK then if you have a fuel burning heater unplug it to rule it out of the equation - there is a sequence as to how to do that which is listed on the forum which I'm sure someone will help you with.

A failing alternator diode can drain the battery and if you have a factory fit Sat Nav that may not be shutting down and causing a current drain.

If all the above are OK then you need to use an ammeter and do a bit of digging to find the root cause.

.

Kernowchristoff · 15th December 2019, 17:27

I have the 115 CDT diesel.

oswestryalex · 15th December 2019, 18:58

i had a battery drain issue when I first got my MG ZT - turned out leavinf the satnav disc in the system made it drain the battery, and removing it cured that problem. Check for any drain sources, and then move on to the alternator if need be. Mantra is - check cheapest first, and move up...

COLVERT · 16th December 2019, 18:45

To check alternator output get a voltage reading at the battery terminals on tick over.

You should see 14 to 14.5 volts .

Comfortably Numb · 16th December 2019, 23:16

Quote:

Originally Posted by COLVERT

To check alternator output get a voltage reading at the battery terminals on tick over.

You should see 14 to 14.5 volts .

However, your battery could still drain through faulty diodes when you switch the engine off.

COLVERT · 17th December 2019, 20:05

Quote:

Originally Posted by Comfortably Numb

However, your battery could still drain through faulty diodes when you switch the engine off.

Very true as there are a number of things that can make your battery discharge and need to be tracked down.

MarkS · 18th December 2019, 04:01

I don't know how much of an old wives tale, the alternator diode is. My thoughts are that while diodes can fail short circuit, and cause the above issues, I would have thought that large currents from the alternator and battery would subsequently blow a failed diode open circuit. YMMV.

Then there is the wipers that can turn themselves on for no apparent reason ! And which happens predominantly in damp weather. And is definitely known to afflict the R75.
https://the75andztclub.co.uk/forum/s...ighlight=Wiper
That could flatten a good battery in hours. Removing the associated fuse or relay is a quick and easy way to confirm the wipers are not the issue.

And a load space boot light that never goes off. But should take days to flatten a good battery.

And the satnav failure to shutdown issue is known to afflict the R75. Although the thought is that that takes days to flatten a good battery, not hours.

I believe that Lidl are doing a Bluetooth car battery monitor that transmits the battery voltage to a paired Bluetooth phone. Could be useful !

Edit: BM2 battery monitor on eBay £14.99

15th December 2019, 15:20	#1
Kernowchristoff Avid contributor Rover 75 Tourer Connoisseur Se hi line Mk 1 115 CDT Join Date: Dec 2012 Location: Par Cornwall Posts: 102 Thanks: 89 Thanked 16 Times in 12 Posts	Battery Drain Hey Guys After having a terrible time with an electrical issue a month ago with a certain high street auto repair shop ive now got the same problem. Last week came home left my tourer for a day, Came out turned the key and again flat battery. The message centre gave me no indication of a voltage drop. A mobile mechanic out since the car is stuck in the garage. The Alternator was charging when he jumped her. However after £60 his diagnostic was too new for the car. Later on about 8pm went out the battery was flat. Ive had a new battery fitted although it is a halfords one. My mind is saying alternator after almost 18 years and 216,000 miles maybe a replacement. Thoughts please i am tearing my hair out i dont want to scrap her.Way to good for that.

15th December 2019, 15:33	#2
Mike Noc This is my second home Rover 75 CDT Manual Connoisseur SE, Rover 75 CDT Automatic Connoisseur SE & a Freelander Td4. Join Date: Jul 2009 Location: Hampshire Posts: 11,548 Thanks: 3,470 Thanked 3,119 Times in 2,247 Posts	Chris always helpful to know the engine type on faults like this - if you add it under the description saves people having to look it up. First thing is to eliminate the battery so charge it up fully on the bench and leave it overnight then fit it and see if it has lost any power whilst resting. If the battery is OK then if you have a fuel burning heater unplug it to rule it out of the equation - there is a sequence as to how to do that which is listed on the forum which I'm sure someone will help you with. A failing alternator diode can drain the battery and if you have a factory fit Sat Nav that may not be shutting down and causing a current drain. If all the above are OK then you need to use an ammeter and do a bit of digging to find the root cause. . Last edited by Mike Noc; 15th December 2019 at 17:46..

18th December 2019, 04:01	#8
MarkS Gets stuck in Rover 75 Diesel Tourer, called Perseverance Join Date: Nov 2011 Location: Bournemouth Posts: 664 Thanks: 189 Thanked 157 Times in 108 Posts	I don't know how much of an old wives tale, the alternator diode is. My thoughts are that while diodes can fail short circuit, and cause the above issues, I would have thought that large currents from the alternator and battery would subsequently blow a failed diode open circuit. YMMV. Then there is the wipers that can turn themselves on for no apparent reason ! And which happens predominantly in damp weather. And is definitely known to afflict the R75. https://the75andztclub.co.uk/forum/s...ighlight=Wiper That could flatten a good battery in hours. Removing the associated fuse or relay is a quick and easy way to confirm the wipers are not the issue. And a load space boot light that never goes off. But should take days to flatten a good battery. And the satnav failure to shutdown issue is known to afflict the R75. Although the thought is that that takes days to flatten a good battery, not hours. I believe that Lidl are doing a Bluetooth car battery monitor that transmits the battery voltage to a paired Bluetooth phone. Could be useful ! Edit: BM2 battery monitor on eBay £14.99 Last edited by MarkS; 18th December 2019 at 05:16..

15th December 2019, 17:27	#3
Kernowchristoff Avid contributor Rover 75 Tourer Connoisseur Se hi line Mk 1 115 CDT Join Date: Dec 2012 Location: Par Cornwall Posts: 102 Thanks: 89 Thanked 16 Times in 12 Posts	I have the 115 CDT diesel.

15th December 2019, 18:58	#4
oswestryalex Loves to post Rover 75 1.8T connoisseur saloon 2003 in blue , MG ZT 190+ 2003 Join Date: Jul 2012 Location: Oswestry Posts: 308 Thanks: 159 Thanked 99 Times in 57 Posts	i had a battery drain issue when I first got my MG ZT - turned out leavinf the satnav disc in the system made it drain the battery, and removing it cured that problem. Check for any drain sources, and then move on to the alternator if need be. Mantra is - check cheapest first, and move up...

16th December 2019, 18:45	#5
COLVERT This is my second home R75 Saloon. Join Date: Feb 2009 Location: France/or Devon. Posts: 14,003 Thanks: 3,851 Thanked 2,167 Times in 1,816 Posts	To check alternator output get a voltage reading at the battery terminals on tick over. You should see 14 to 14.5 volts .