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MG MGF Technical - Woes Part Deux - battery ? fob ? Alternator ?

Could really do with some advice,

1. Car broken into while on holiday so getting new roof i.e. they cut hole (thanks for rec carhoods.com)

2. battery went dead before and after hols

Shortly before i went on holiday i got locked out of my car as the when i activated the fob the central locking wouldnt work.

I got a new battery to replace the original in there from halfords which matched upto mgf model i have. (98 1.8i)

Everything was okay. I do remember at the time activating my fob and hearing the central locking make a rattling noise before actually locking ???

so new battery and all is ok. except after i got back to find car broken in....

the battery is flat again. My friend jump started me fine. I drove the car for 45 mins to work no probs. I now just went in teh car park to start her up and the battery has faded again. Also i've noticed the same central locking rattling before actually locking again ?

So is my flat battery due to .....

1. prob with fob (do i need new battery in it ...i think it struggles ?)
and subsequently can the fob cause the car to eat my battery juice via the central locking ?

2. alternator (what does the alternator do ?)

or something else.

Theres obviously a drain but where from is a mystery.


help would be valued as i want to try and diy...the car is costing me lots of money via dealers though i do have a warranty with warranty direct.

Jimm
Jimmy

The alternator turns rotational movement of the engine into electrisity to charge the battery. If you have a volt meter:
open the boot
start the car
run for a while
open the bonnet with the engine still running
measure the voltage across the battery terminals
the voltage should be between 14.5 volts and 15.5 volts, if not then the alternator is probely shot.
Will Munns

I think that there may be a couple of separate problems here.

1. A problem with the central locking: clattering is often a sign of a poor electrical connection to the central locking motors in the doors.

2. A problem with the car's battery: charging/discharging.

Will's test will tell you whether there is a problem with the alternator/charging circuit.

However, it is important to note that brand new batteries are often supplied without a complete charge. A 45 minute drive ought to be enough to bring it up to near full charge, but it depends on whether you've managed to keep the engine speed above 2500rpm. 45 minutes in stop start traffic won't be enough - especially if the radio and other electrical devices etc have been switched on as well.

Assuming that there is a problem (see if the battery does flat again once you are confident that it has a full charge), then you need to suspect a current drain. The central locking/ alarm/ imobiliser system is unlikely. More likely is a problem with the boot lamp circuit - with the wire shorting to earth thanks to a break on its run next to the boot hinge, or with the lamp not switching off. Alternatively, occasionally, MEMS can have a fault whereby it fails to go to 'sleep' after ignition off...

So a couple of things to check there Jimmy - keep us posted on how you get on.
Rob Bell

Most battery dealers will be able to do a test to check the charge voltage of the alternator.

I cannot believe that a key fob problem would cause the battery to go flat as either the central locking works or does not work.

As for a battery drain maybe something simple like the boot light staying on as this is not something new as Rob mentioned.

Tom
Tom Randell

Okay gr8 stuff,

I have an alternator tester whilst it doesnt tell me the volts over the battery it does tell me after the engine is running whether the alternator is okay i.e providing enough power which it says it is - it also shows me the percentage of charge on the battery which it records as 75-100.

I've tried this with electrics all on and then all off with engine running and its been coming up correct.

So i dont think its alternator problem and will rule out.

When i turn the engine off and attach my battery analyser it shows 25 % charge.

So i'm gonna start with your advice and fully charge the battery. Also i've noticed some yellow chalky residue on the battery clips (i hope its not something simple like not enough contact!! So i'll clean these aswell).

fingers crossed all will be ok.

With regard to the central locking its fine unlocking its having problems double locking.

will let u know how all goes.

Jimmy

>central locking its fine unlocking its having problems double locking.

Problems - like it won't do it or it clicks a lot - if it wont lock it is due to a problem as Rob describes (it won't double lock whilst a door or bonnet or boot is open)
Will Munns

it locks but when you try and double lock there is lots of clicking.

I was going to the following that i found in the archives is this a good place to start ?

Alarm system test
The alarm system can be tested by following the procedure described below:
1. Ensure doors, bonnet and the boot lid are closed.
2. Sit in the driver’s seat and close the door.
NOTE: The next three actions must be carried out within 2 seconds.
3. Depress the driver’s doorsill button.
4. Switch the ignition on, off and on again.
5. Raise the driver’s doorsill button.
If the test mode has been entered correctly, the horns will give a short beep and the engine

immobilisation buzzer will sound.
Opening either door, the bonnet or the boot lid, or operating the driver’s doorsill button, will cause

the alarm LED to illuminate for approximately one second. If the LED does not illuminate, there is a

system fault.
The volumetric sensor can also be tested while in test mode. To test the volumetric sensor, press the

unlock button on the remote handset several times. The alarm LED will illuminate for approximately 1

second each time movement is detected in the vehicle.
The test mode is cancelled by switching the ignition OFF.
jimmy

okay well i dont need to do that above.

The alarms seem fine...as i set them off the turned off again

I do have a question though.

My central locking seemed a bit intermittent as in i turned the engine off and usually the alarm light comes on after a while as the engine immob kicks in ??? is this right ??

cos in this instance i did not notice the light on...or does the door have to be shut ?

anyway also notice some wires far behind teh accelarator pedal are these for the central locking ? i think i read that somewhere ?

so i gently pushed these and my fob and central locking seems a lot more repsonsive ?

should i be even able to see these or should they be tidyed away ?


jim.
jimmy

This thread was discussed between 01/07/2004 and 02/07/2004

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