Morris Minor Owners Club

seems im kiiling batteries at an alarming rate. personally is uspect my lighting wiring, as without any lights on the car runs lovely. however when i turn my lights on for any peroid of time the battery just vanishes to the point the ignition light start to flicker if i leave the engine at tick over.
i originally put this down to the battery so i replaced it with the very nice large battery from my granada, gave it a full charge and a week or two later its happening again!

my wirings abit of a mess os i originally suspected a short somewhere, anywhere in my car, but after a fwe days of driving only during daylight with no troubles leads me to believe its just a lighting issue.

problem is, surely if i had a short my lights would fail to work all together as the connection would just bypass the bulbs? but as it is theyre lovely and bright. my other theory is i have a bad connection in there somewhere, or that my earths are in a poor location in relation to the battery (i have the lights earthed through the radiator) but as i= v/r if i had a large resistance from a bad connection, current would fall not increase, and as power =i^2*r i cant see how that would produce enough power to kill a battery.

any ideas gentlemen?

if I had a short my lights would fail to work all together

Not sure about that, I'd be looking for lighting wires that are getting hot.
Does it happen on side lights or only headlights?

only head lights, or so it seems.

phurn wrote:the ignition light start to flicker if i leave the engine at tick over.

have you tried speeding up the tickover? with lights on you're putting a greater demand on the engine which will slow it down.

are you using a dynamo or an alternator? if you've never changed whatever you have, it could be the charging that's not working right, not necessarily the battery at fault.

i believe its an alternator, though tbh ive only given it passing inspection.
out of interest wheres the tick over adjustment?

i can't find a picture for you, but it you follow your accelerator cable to the carb, you will find the throttle lever. this lever type thing has a 'stop' which is adjusted by a small screw. if you're looking at it from the front it'll be just to the left of the dashpot (bell-shaped thing on top of carb).

if you're struggling i'll take a pic for you

First things first, get a voltmeter (voltage function on a multimeter, either digital or analogue is fine. Measure the voltage across the battery terminals (a) with the ignition off, (b) with the engine running at fast tickover with the lights off, and then (c) as for (b) but with the lights on.

Is the fan belt adjusted correctly? With lights on, there is a greater load on the charging system, and if the fan belt is loose then it might slip and fail to charge correctly. If we need to look at the wiring then we need to know whether the car has a dynamo or an alternator. It's not difficult to check!

[frame][/frame] C39 Dynamo[frame][/frame] Alternator

i definatly have a big fat alternator. i know its charging atleast to some degree as when the battery is low and i rev the engine the lights get brighter.

well ive missp;alced my multimeter now so thats a shame =[ on he other hand i did increase tick over a touch as it soundd a li low to me anyway, and while the drain appeared ot be better, it still hasnt gone away so im douting low tick over was the problem.

shame really, i was hoping ot avoid chopping the wires up as theres ben alot of replacements and bodgery... and everythigns ben replaced with red wire!!!!!! how infuriating.

It's nothing to do with the lighting - unless you have added many extras ? It's all to do with poor charging - as already suggested - have you tightened the fan belt (or even better - fit a new one!)? The fact the lights get brighter confirms it IS charging at least to some extent!!

I haven't changed it but I've inspected it and it seems healthy and tight. Its maybe just coincidence I've only had this problem since I replaced the headlight then? Before then the car ran like a dream.

Tbh I've assumed its charging fine because if I sit at highish revs for a min or two everything runs as normal for about 10 mins before things do dim again, ill have to look at my alternator then!
I do hear my indictor relay click in everynow and then so I think there's a slight short somewhere anyway.

If the belt is worn - it can be tight but sitting in the base of the V groove and slipping under power.......

ill have a look on friday, though id have thaught if that was the case it'd charge better at tick over than at revs? when infact the opposite is true.

An alternator can manage a bit of charge at tick-over - but not the full business. Also belt less likely to slip at low revs.......

thats my point, if its slipping wouldnt it charge better at low revs? where as i ahve to rev it to get it to do anything =/

It may very well NOT be the belt - I just suggest it's the easiest/cheapest thing to check !

and ofcourse ill check it. i wasnt critising your suggestion, merely trying to understand why it might be that?

Friction drops with speed, the faster one thing moves across another the less friction there will be.

Fan belts work on friction.

Driving in the snow and ice shows the effect nicely, at tick over or just above you can get the car to move.
Give it too many revs and you wont get anywhere, and more revs make it less likely to move, not more.

ok so ive been playing all morning and eventually noticed my alternator is kicking out about 12.8v at tick over, if i really rev it it'l go up to 14 odd volts but i assume this isnt normal behavoir? so i set about cleanign up all my connections, making sure the earth is good. and between the alternator earth and the battry i get a reading of about 0.7ohms which i consider more than acceptable! same goes for the engine block so im hapy with that. now when im running the car i get a battery voltage of 12.1 then it slwoly rises and sits at 12.8-9. however if i turn anything on it drops to 11.8 so things are not good.


as per, i checked the fan belt, and t looks ight enough and in good condition, however i noticed i could turn the alternator over by hand with the belt staying in the same place so maybe slippage is an issue there as i preume im not ment to be able to do this?