Battery drain

SomersetJeff · 18th March 2023, 18:52

I've had an issue on my 2.0CDTi tourer with battery drain. Put the car on charge a couple of days back and, when I came back to the car (left it unlocked, bonnet open so nothing to wake the car up), I could hear something humming slightly in the engine bay towards the front offside, so it sounds like something is staying alive and draining current.

Any pointers where to start would be gratefully received. Thanks.

Briodyjl01 · 18th March 2023, 20:58

Does it have high line nav?

SomersetJeff · 18th March 2023, 21:27

No, just about the only thing it doesn't have.

YHT · 19th March 2023, 08:22

Bought a car with this problem; it was the satnav/radio.
I disconnected the -ve from the battery and put a multimeter set to amps between the terminal of the battery and the disconnected cable. Them pulled the fuses one by one (putting them back in straight afterwards) until I found one that when I pulled it out the current dropped. It was the radio/satnav which has now had the fuse out for some 3 years; really must get around to reading up all the advice on the issue thats been posted on this site. I see you dont have a sat noav but the technique should enable to trace the drain on the battery. Helps to have someone keep and eye on the multimeter if you are delving under the dash in the cabin fuse box. Good luck.

KWIL · 19th March 2023, 08:59

Quote:

Originally Posted by SomersetJeff

I've had an issue on my 2.0CDTi tourer with battery drain. Put the car on charge a couple of days back and, when I came back to the car (left it unlocked, bonnet open so nothing to wake the car up), I could hear something humming slightly in the engine bay towards the front offside, so it sounds like something is staying alive and draining current.

Any pointers where to start would be gratefully received. Thanks.

Windscreen washer motor?

SomersetJeff · 19th March 2023, 16:23

Probably a bit further forward than the washer motor, I probably need a stethoscope to work out where it is as well as trying the fuses. I guess the washer motor would be switched live as well whereas this is always on.

SomersetJeff · 10th April 2023, 10:26

Been doing a bit more investigation (with a stethoscope) on this before starting to pull the fuses. Seems like the hum I'm noticing is coming from the alternator. As soon as the battery is connected, the alternator hums. Is that normal?

Ducati750cc · 10th April 2023, 12:32

Quote:

Originally Posted by SomersetJeff

Been doing a bit more investigation (with a stethoscope) on this before starting to pull the fuses. Seems like the hum I'm noticing is coming from the alternator. As soon as the battery is connected, the alternator hums. Is that normal?

No it's not normal, the hum will be caused by one or more diodes failing in the alternator diode pack.

A diode is, to put it simply, a one way valve, it allows current to flow only one way.

When they fail, two things happen, one when the engine is running the alternator output reduces so the battery charging is less than optimal, two with engine off it allows current to flow from the battery to the alternator discharging the battery.

The packs can be replaced with a bit of stripping down and soldering and are not overly expensive, around £25 for an average alternator, but going by it's age, there is the chance of further components failing down the line and being that they are not the easiest to get at, it would be better to get a new one, a good reconditioned one, or take yours to an alternator / starter motor re-conditioners.

When diodes fail, with the engine running, there is sometimes the faint smell like hot resin around the alternator and it may feel hotter than it should to the touch.

It wants doing sooner rather than later, in the meantime you will need to disconnect the battery when parked for any length of time to prevent ending up with a flat battery.

If you have access to a clamp ammeter, clamp it around the thick red output lead from the alternator, with engine and ignition switched off you will find current flowing, a higher parasitic draw he expected..........there should be just a few milliamps, if it is one or more amps a sign of a faulty diode.

Or if you have a DVM, set it to AC not DC and put the probes on the battery terminals with the engine running, there should be no AC voltage showing, if there is it's another clue to a faulty diode.

Mike Noc · 10th April 2023, 19:30

Quote:

Originally Posted by SomersetJeff

No, just about the only thing it doesn't have.

Does it have a fuel burning heater?

SomersetJeff · 11th April 2023, 08:17

Thanks, Ducati750cc. I will try the DVM across the battery and see what results I get. It does sound like this is the issue - alternator hums and then if I leave it connected for any length of time, the battery is dead.

Looking at where the alternator is located, it looks like abit of a nasty job to replace.

Quote:

Originally Posted by Ducati750cc

No it's not normal, the hum will be caused by one or more diodes failing in the alternator diode pack...

18th March 2023, 18:52	#1
SomersetJeff Regular poster Rover 75 Tourer Join Date: Jul 2021 Location: North Petherton Posts: 65 Thanks: 0 Thanked 1 Time in 1 Post	Battery drain I've had an issue on my 2.0CDTi tourer with battery drain. Put the car on charge a couple of days back and, when I came back to the car (left it unlocked, bonnet open so nothing to wake the car up), I could hear something humming slightly in the engine bay towards the front offside, so it sounds like something is staying alive and draining current. Any pointers where to start would be gratefully received. Thanks.

18th March 2023, 20:58	#2
Briodyjl01 Gets stuck in Rover 75 Tourer, Rover 75 Saloon Join Date: May 2018 Location: Castleford Posts: 978 Thanks: 237 Thanked 185 Times in 113 Posts	Does it have high line nav? __________________ Too many Rovers to count ……

18th March 2023, 21:27	#3
SomersetJeff Regular poster Rover 75 Tourer Join Date: Jul 2021 Location: North Petherton Posts: 65 Thanks: 0 Thanked 1 Time in 1 Post	No, just about the only thing it doesn't have.

19th March 2023, 08:22	#4
YHT Loves to post Rover 75 Saloon Join Date: Jun 2017 Location: suffolk Posts: 270 Thanks: 46 Thanked 25 Times in 23 Posts	Bought a car with this problem; it was the satnav/radio. I disconnected the -ve from the battery and put a multimeter set to amps between the terminal of the battery and the disconnected cable. Them pulled the fuses one by one (putting them back in straight afterwards) until I found one that when I pulled it out the current dropped. It was the radio/satnav which has now had the fuse out for some 3 years; really must get around to reading up all the advice on the issue thats been posted on this site. I see you dont have a sat noav but the technique should enable to trace the drain on the battery. Helps to have someone keep and eye on the multimeter if you are delving under the dash in the cabin fuse box. Good luck.

19th March 2023, 16:23	#6
SomersetJeff Regular poster Rover 75 Tourer Join Date: Jul 2021 Location: North Petherton Posts: 65 Thanks: 0 Thanked 1 Time in 1 Post	Probably a bit further forward than the washer motor, I probably need a stethoscope to work out where it is as well as trying the fuses. I guess the washer motor would be switched live as well whereas this is always on.

10th April 2023, 10:26	#7
SomersetJeff Regular poster Rover 75 Tourer Join Date: Jul 2021 Location: North Petherton Posts: 65 Thanks: 0 Thanked 1 Time in 1 Post	Been doing a bit more investigation (with a stethoscope) on this before starting to pull the fuses. Seems like the hum I'm noticing is coming from the alternator. As soon as the battery is connected, the alternator hums. Is that normal?