6 replies to this topic

[JaiminPatel]

Hey all,

 

I've had a '95 Rover Mini for 2 years now and this problem started almost a year ago, whenever I switch the lights on (with the engine running) the battery drains no matter if its sidelights or dipped beams. The battery charges if the lights aren't used and holds its charge normally too.

 

My experience with fixing cars is not great so I took it to a garage where they replaced the battery and alternator, the car was working well for a brief time before the same problem came back. The engine earth strap has also been replaced recently and the battery earth strap hasn't rusted.

 

I was wondering if it could have anything to do with other electrical faults like the headlight flasher which stopped working around the same time the problem started or the break lights which stopped working as well. 

 

It would be great to not be limited to using the car in broad daylight.

 

Any suggestions and opinions about what's causing the problem are most welcome!

 

Thanks!

Edited by JaiminPatel, 17 July 2017 - 08:18 PM.

[phillrulz]

Hey all,

 

I've had a '95 Rover Mini for 2 years now and this problem started almost a year ago, whenever I switch the lights on (with the engine running) the battery drains no matter if its sidelights or dipped beams. The battery charges if the lights aren't used and holds its charge normally too.

 

My experience with fixing cars is not great so I took it to a garage where they replaced the battery and alternator, the car was working well for a brief time before the same problem came back. The engine earth strap has also been replaced recently and the battery earth strap hasn't rusted.

 

I was wondering if it could have anything to do with other electrical faults like the headlight flasher which stopped working around the same time the problem started or the break lights which stopped working as well. 

 

It would be great to not be limited to using the car in broad daylight.

 

Any suggestions and opinions about what's causing the problem are most welcome!

 

Thanks!

Follow your post, top right that way you will get notifications when someone replies, Hmmm i know you said about the new engine strap and battery strap but id feel inclined to measure a resistance from the engine / alternator body to the actual battery negative. But i feel its more likely engine side. Working on the idea once its cranked the alternator and engine could in theory work as a floating earth system. 

[cal844]

Have a look behind the speedo binnacle(clocks) there may be some inline fuses(blue/red/blue/white wires) are the white plastic fuse covers melted?

Ow remove and clean the earth terminals behind the ECU(large crosshead screw) to clean metal then also clean the 3 way connection near the alternator behind the grille.

Also remove and clean all connections at the fusebox(remove the foam sound deadening pad from this area of bulkhead if fitted)

[Sask_Mini]

I'm not a mini expert but I do know electrics.  It sounds to me like you have a low resistance short to ground, could be a bare wire that is shorting against the frame of the car somewhere.  It's strange that you wouldn't find any blown fuses though if that was the case.  It would take a fair amount of current to drain a battery while the car was running.  

 

If it was me the first thing I would do is take a multi-meter and measure the voltage across the battery terminals with the car running and without the lights on.  You should see somewhere around 14V.  Then do the same thing with the car running and the light switch on, the voltage at the battery should remain the same.  If it drops way down to 12V or lower then it means one of two things.  Either you have a short somewhere in the wiring that isn't going through a fused circuit or your alternator is weak and can't keep up with the increased load caused by the lights.  My gut feeling based on the fact that you are having some other electrical issues is that your alternator is alright but you have some wiring that is frayed/loose/corroded.   

[KernowCooper]

My first check would indeed be a charging check with the engine above 2500rpm with the lights off and as mentioned above your looking for around 14v, if ok then repeat the test with the lights on at the same revs, if then ok at around 14v then decrease the revs slowly down to idle and watch the voltage, if this drops down to 12v and below unlike a older car ones with a ecu will require a higher voltage and cut out.

 

Do the charging checks and shout back.

 

Its not unknown for some of the replacement alternators to die quite quickly, some replacements are very poorly made/reconditioned.

Edited by KernowCooper, 20 July 2017 - 09:03 PM.

[JaiminPatel]

Thank you very much for the suggestions, I've just checked the voltage across the battery when running and even without the lights on it's at 12.5 volts and any electrics I use decreases it further. Do you think I would need to replace the alternator again for a stronger one?

[Sask_Mini]

Sure sounds like a bad alternator to me, or a bad cable connection to the alternator.  Most part shops have a machine that can test an alternator, so if you take it off and take it in to them they could confirm that the alternator is indeed bad.

 

Or you could take it back to the shop that replaced your battery and alternator and tell them that it failed in relatively short order.