Morris Minor Owners Club

After much playing about and checking thigns over we came to the conclusion the batteryb was at fault... she has a new battery now .... but that hasnt solved the problem

My problem is that the battery keeps going flat, so i imediatly put the blame on the dynamo, the lights grow brighter when i increase the power however so i wondered if that meant my dynamo is infact not at fault
Could the voltage regulator have anything to do with this problem? I'm a little confused

Thanks

Tris

how long does it take to flatten the battery?

Moved to 'electrical', as it seems to be an electrical question, not a mechanical one

Thanks BigG .. forgot about this section

erm... 24 hours in this case, did a 100 mile trip yesterday though and shes been out a bit today too

Tris I suppose you did test the battery to make sure it has lost charge and that it not something like the engine earth strap giving up the ghost intermitantly.

yes it had, after 24hrs on the charger its fine....

something is still drawing current even when it is turned off. you need to buy/borrow a mulitmeter with an ammeter function, and take each of the 3 fuses out (2 in the fusebox and the other just below it) and see if any current is flowing across the fuse terminals. It will be difficult to trace the source of the current "leak" but by finding out which fuse the current is going through this should help to find out what electrical device is to blame. and if it sounds tricky just think how difficult it would be in a modern car fusebox!!

As above I suspect a current drain when the key is switched off.

Turn off the engine and check fuses as above, or quicker is to disconnect the battery and check for a current drain there (ALWAYS use the highest current range on the meter first and work down until you get a reading).

Have you fitted anything new thats always connected? Radio etc?

24 hours is a fair time to discharge the battery, so the drain is reasonable.

It may be that the key switch has worn, and when you remove the key it is turning back on the ignition circuit thus draining your battery through the coil? You can check to see if there is a voltage at the coil with the key removed.

if the regulator is faulty it may be connecting the dynamo to the battery when it should not, check to see if there is a voltage across the dynamo with the key removed or indeed with the engine simply stopped.

Take care with all the above, if the ignition is being left live then there is a small chance that the engine can be started with a jolt, or at least an ignition spark can be produced. If the dynamo is being powered by a fault in the regulator then it will be trying to act as a motor and trying to move.

If the Ignition switch was turning itself on then the coil would burn out pretty quickly so it would not appear to be that problem.

I had a problem like that a few weeks ago- and wrongly suspected the regulator. It turned out to be simply the "fan" belt needed tightening as the belt was too loose on the dynamo pulley. See if you can easily turn the dynamo pulley by hand - causing the belt to slip.

I had Grandpa checking for current flowing across fuses and through other components in the engine, will check again and the fan belt also. so if the lights are brightening there is definately nothing wrong with the dynamo? My mate rekons that it may not be charging the battery "enough" but i dunno... i hate electrics!!!

There might be nothing wrong with any of the electrics, but simply that the fan belt is not turning the dynamo properly, as John says.

I had the same problem: against the load of headlights, wipers and heater fan the belt was slipping and not turning the alternator fast enough. It was turning enough to keep the equipment working but not enough to charge the battery as well. Tightened the belt and it's fine.

mines very tight if anything, its not slipping at all.
when checking for a current/power in the battery i got a reading of 10 volts. the earth wire is intact and in good condition also

The next most likely cause after 1. loose belt, 2. dodgy battery is 3. Dynamo brushes on the way out.

I would suggest removing the dynamo and stripping it to inspect carbon brushes- if worn, then replace.

Before removal it may be worth doing a charging voltage check. Put your meter on its dc voltage range across the battery. On tickover it should show about 12v, rev up to about 2000rpm and it should show between 13 and 14.4 volts any less and the dymamo is not giving any output. To check the regulator remove the cover and look at the contacts, raise the engine revs and you should see the contacts move as the dynamo starts to charge. From your post it sounds like you have something draining the battery but it does'nt hurt to check things.

Your 10 volts is desperately low. But if the lights brighten - then it must be charging. Try taking the lead off the battery after a good run in daylight. Next time you go to the car - reconnect obviously - is the battery still ok ?