18 replies to this topic

[Noah991]

I have taken my mini to have the electrical looked at and no answer was found. Here is the prob, the battery is not fully charging. When I drive down the road with the lights on, wipers on, and turn on the rear defroster, it draws all the electical power. The wipers even stop. It not only happens with all those on, just lights and wipers kill it. Had the battery checked and alt checked and mechanic said both were fine. Any suggestions.

[Tom Sanderson]

could be a short in the wipers or lights

[Noah991]

I have tried looking for a short and no luck so far. Also, it does it without the lights or wipers on. Seems every 4-5 days it dies, no matter how long I drive it.

[Tom Sanderson]

have you had a look underneith to see if the battery cable has been chafing on something and when you start the engine it moves about and catches on the body flatning the battery

[Bounce]

do you get a red light on your dash with the ign on?


also have you checked the battery voltage with the engine off (around 12v) and the engine on (around 14v) this indicates if the alternator is charging the battery or not.

[cooper_shaz]

do you get a red light on your dash with the ign on?

This is a crucial part of the charging system as it completes the circuit....

If it is fused you battery charging circuit is incomplete, have a look through the old posts here as this has came up many times

cheers

[Noah991]

No, no red light comes on while driving. Also, just ran it for over an hour after getting it jumped and when I made it home had to turn it off for less than one minute to open garage door and it was completely dead. Did not run the lights, wipers or anything while driving. Had the battery and alt checked about three weeks ago and the mechanic said they were fine. Will have them re-tested...

[dklawson]

Let's elaborate on the charge indicator light question.

Is the charge light on when you switch on the ignition... BEFORE you start the engine? It needs to be.

As mentioned, the lamp has to be working to power the field coils of the alternator before it gets up to speed. If the lamp is disconnected or burned out, even an otherwise fully functioning alternator will fail to make any electricity.

[Bounce]

Let's elaborate on the charge indicator light question.

Is the charge light on when you switch on the ignition... BEFORE you start the engine?

And if it is, get a cheap multi meter and check the voltages over the battery yourself. If your battery voltage is low (should be 12V) then charge your battery over night with a car battery charger.

If the voltage is extremely low (less than 8V) you will need to buy a new battery, or your battery charger may have a re-conditioner function for flat batteries, this works for a while but ultimatly your battery will not hold its charge for very long and you will have to charge it every time your car is standing for a while.

If the battery is flat or only holds a few volts, check the electrolite levels (the water surrounding the plates inside). ensure the elctrolite is completely covering all the plates. If there is little or no electrolite in the battery, it is quite possible that your battery is shorting to earth somewhere (boiling off the electrolite). To check this, disconnect the positive lead on your battery, and with your multi meter set to the omega symbol, connect a multi meter lead to the positive battery lead and the other to the negative lead. If the reading is between 0 and 10 ohms you have a short to earth and thats what is discharging your battery. After the short is fixed you will need a new battery.

[icklemini]

Check all the earths - Alt to engine, engine to body, body to battery...

TTFN,
Dave

[Noah991]

The batter light does come on when i turn the key, before starting the engine. Will try to find a multimeter in the next day or so and check the battery. The battery is sealed, so can not check the fluid levels

[THedooBZ]

im having the exact same problem with mine at the moment, yesterday i drove home from work got out of the car to open the garage and it refused to start back up.
the battery is new and the alternator charges the battery.

does anyone know what reading the alternator should have when the engine is running???

[Bounce]

normally between 13-15V

[THedooBZ]

well thats my prob sorted then, when the ignition is turned on its 12v but when the engine is running i only get an output on the alternator of 0.5v.

then again could change it to find that its a fault in the loom.

[Bounce]

You can measure the output from the alternator, depending on what type of alternator, there is normally a plastic cover covering the contacts (3 of them) on the left hand side as you look at it. Put you multi meter on the two outer contacts and that'll prove if its you alternator. Also as stated before, ensure that you get a red light on the dash before you start the engine and that it goes out when the engine is running. The lamp completes the circuit allowing your altinator to trickle charge your battery