Morris Minor Owners Club

Sorry if this has been asked before but...

Last week I came to start the old gal and there wasn't enough power from the battery to start the engine. All the lights came on as usual but the couple or three times I fired her up the power drained to nothing. I bump started her and got to work. After work the same thing happened and I bumped her again. At home I recharged the battery overnight and for a week everything has been fine. Today the same problem again, little or no power to fire up.

I've been checking that everything has been turned off when parked up so I know that isn't the problem. I run the car everyday to and from work, a round trip of 14 miles and on my rest days for running errands etc.

Where do I go from here, do I start with a new battery, I've checked the terminals, and all is ok. How do I check the dynamo and other bits and in what order. I'm less than brilliant with eletrical things but am willing to have a go myself rather than pay £30-£40 PH for someone else if it is simple enough.

Other than this problem she is a fantastic little motor (shes a 1960 948)
All advice gladly welcome,
FUNKY

Sounds very much like a battery which is on its way out.

How old is the battery ... have you ever replaced it?

If its pretty old, then its probably worth replacing it, if its pretty new then have your charging circuits checked out BEFORE you replace the battery.

You may be able to get away with adding some bat-aid tablets, and topping up the levels, but that's only really worth it if the battery is relatively new.

hi
are you sure everything is off.and no electrical leaks.
i had a similar problem and discovered i had forgotten to take the key out of my immobiliser

have the battery checked.


check the charging system. does the ignition light go out when engine is running above idle.
if no then the dynamo could be at fault, possibly brushes.

could even be the regulator.

After you had charged the Battery did you check it with a hydrometer as with older batteries this soon shows up any duff cells that are on the way out.

You can also check the dynamo by reving the engine with the headlights on, they should shine brighter. This is more noticeable when the battery is low. Mind you this doesn't tell how much it's charging.

Halfords still sell Hydrometers, but battery acid is hard to come by!

They also sell tablets (in a little tube) that revitalise old / tired batteries. My battery used to be good for about 3 starts (and that car starts well) after a full charge. I popped 2 tablets into each cell, charged the battery for 24 hours and have had no problems since.

The hydometer still says the charge isn't optimal (neds topping up with acid), but it's a lot better than it was.

Ben

The Hydrometer measures the specific gravity of a battery not the acid content, over time particles fall off the cells to the bottom of the battery and in the end the particles cause a form of short circuit between the cells, thats why when you use a hydrometer you can get 2 dead cells and the rest is still OK.

OK Chemistry part 2...

Battery cells are filled with diluted sulphuric acid. When the battery is charging, the plates change chemically, and release hydrogen from one plate, and oxygen from the other.

In effect, the water in the acid is being turned into hydrogen and oxgen - it's just the right proportions to form water, and this is actually a nice explosive mixture (just the right proportions) - so don't examine a charging battery with a match"

The sulphate part of the acid doesn't go anywhere, and all the hydrometer is really measures is how charged the battery is - you shouldn't need to top up with anything other than purified water (unless you tip the battery over and spill the acid). As the battery ages, bits drop off the plates, and because these are very close together, the plates can short out, resulting in a dead cell. At that stage, it's far simpler and more reliable to buy a new battery..

Colin

Thanks for that Colin I thought I was on the right track and it shows how useful a hydrometer is.

Thanks all..

I've had the battery checked by a local garage and they saw it is fine, there are no problems with it, I've then charged the battery and revved the engine with headlights on and there is a slight flicker only just noticable.
I'm now thinking about taking the Dynamo off and checking the brushes, (what is the cylinder on top of the Dynamo)? Can I get replacement brushes by them selves. What would you recommend next
Thanks

Funky

The cylinder is the ignition coil. Yes, you should be able to get replacement brushes easily enough.

If you remove the Dynamo, then undo the two large screws
on the end plate (where the two terminals are) the end plate
will pull off complete with the two brush holders. Hopefully
you will find that the part of the brush which normally runs
un the copper the copper commutator has a blackened face
as opposed to the normal polished look. The litle coiled springs
which press the brushes down are designed that they will
not actual reach the commutator and ruin it if the brushes wear
too much. replace the brushes anyway and be careful to lift
them up when refitting the end plate

Sorry, I didn't mean to imply that a low hydrometer reading meant you needed more acid, as has been said, it only indicates how charged the battery is.

I said I needed more acid because when I got the battery it was quite low on fluid and even after a top up and long recharge, the reading was still low (about half charge). Having said that it has given me no problems since I put the tablets in - I guess half charged is charged enough!

since I put the tablets in - I guess half charged is charged enough!

Thats OK Ben just keep taking the tablets

LOL!

funky,
if the battery is ok, then you should be able to start the car up to dozens of times.
Get a test done (by a garage.... who will try and sell you a battery regardless )
Or charge it ovenight, and see how many times you can crank it (eg.. disconnect a coil lead)
If you can only turn it over half a dozen times or less, then it can be 2 things - a duff battery or a dodgy starter motor.

If the battery is fine, then worry about the charging circuit, but probably 9 times out of 10 it's just the battery