26 replies to this topic

[fergy26]

Hi, having a serious problem with the mini lately. On tickover the warning light is dimly illuminated however after about 5 minutes of driving it will start getting brighter as the engine is under load. It can get to the point that the car cuts out however if i depress the clutch it will return to the dim glow for a short while.

 

I have checked and cleaned all the earths and the mini seems to be charging ok when on tick over and the fan belt is tight. Any ideas what it could be?

 

Many thanks

Richard

[KernowCooper]

Have you actually checked the charge rate with the engine running at 2000rpm+, it should be between 13.7-14.2v if its not and the belt is tight then it looks like you have a diode pack fault, this will shown up as not meeting the 13.7-14.3v test. Pull the plug from the back of the alternator and see if the terminals are not burnt out.

[dklawson]

As above, start with voltage measurements to determine if the alternator is trying to charge the battery.  

 

In addition to diode problems, I have seen similar behavior on high-mileage units where the brushes have exceeded their wear limit.  

 

Regardless, check the alternator soon and correct whatever is wrong so you do not damage the battery or find yourself stranded somewhere.

[fergy26]

Tried the alternator off my brothers mini which I know works and there is no improvement. The light will glow on tickover but the brightness increases as I rev it. Just trying to find a battery for the multimeter.

Any more ideas to what it could be?

[dklawson]

There are the obvious suggestions for things like clean all the alternator mounting points so there is no corrosion or paint present and of course making sure that the belt is properly tensioned.

 

Since the engine starts you know the engine block has to have a good earth connection.  

 

OK... time to ask what may appear to be a silly question but this comes up every now and then.  You are talking about the red warning light and not the orange one aren't you?  I assume you mean red but the question must be asked.

[fergy26]

Yes defiantly the red warning light haha. I've cleaned everything up but still no luck unfortunately

[dklawson]

The charge warning light connects to the small terminal on the alternator and it only illuminates when the output of the alternator is low.  When you substituted your brother's working alternator for the one in your car the problem should have gone away.

 

All I can suggest at this time is that you start with the plug on the alternator and inspect the loom leaving it going all the way back to the firewall.  If there is any point where the loom and wire insulation has worn through and the small (brown/yellow?) wire from the alternator is touching earth... that could both cause the warning light to stay on and potentially stop the alternator from charging.

 

I am at a loss to make other suggestions.  I will think about this and should I come up with anything I will post again.

[fergy26]

Ok much appreciated, thanks

[lrostoke]

another long shot is that the lights have been swapped

 

have you tried unplugging the oil sender light see if it goes off.

 

other than that assuming 2nd alternator is fine sounds like a bad connection on the wiring.

 

the wiring for the ignition bulb is pretty simple

 

ignition switched 12v supply to one side of the bulb, the earth side is the feed from the alternator.

 

you could make up a test bulb that plugs into the alternator, then you eliminate that side.

Edited by lrostoke, 02 November 2013 - 02:58 PM.

[fergy26]

Quick update, the light seems to stay dim with everything on? I.e lights, main beam, heater. But when I put the hazards on the ignition light pulses between bright and dim?
Also the starter solonoid seems to have a fault, I've tried cleaning the contacts but if I wiggle it about none of the ignition will come on?
Could the solonoid be the source of the problem?

[lrostoke]

power for the car is attached to the solenoid.

 

should be main battery cable plus a lot of brown wires, browns are the main feeds to the car.

 

try tightening the connection

[greenwheels]

power for the car is attached to the solenoid.

 

should be main battery cable plus a lot of brown wires, browns are the main feeds to the car.

 

try tightening the connection

Add 'cleaning and' in front of tightening. As Minis get older corrosion gets in the electrical connections and plays silly games.

[dklawson]

I assume when you say you cleaned the contacts that you mean the threaded terminals.  The actual solenoid contacts are "inside" the unit and typically not serviced.

 

So you start the engine and use the flashers and the light brightens and dims?    

[lrostoke]

come think of it the main charge wire from the alternator attaches to the solenoid battery terminal.

 

So its starting point to issues there

[fergy26]

When I turn everything on and keep the revs constant the light is only dim and then when I turn the hazards on the lights dims a bit more but flashes brighter with the indicators