Flickering headlights

Post by **winger300** » Tue Oct 21, 2003 8:34 pm

When my car is stationary the headlights are fine, but whilst driving the flicker slightly, and the light behind the speedo flickers also.

I have changed the car to negative earth, but i think it has only recently starting happening.

Could a slack fan belt be causing this? Is there anyway of adjusting the tension?

Post by **rayofleamington** » Tue Oct 21, 2003 10:02 pm

Your second question first -
The belt shouldn't be too tight as this will cause damage. If it is too loose it'll slip - I do mine by feel :? but someone will probably enlighten you with the official way to check the belt tightness.
Yes there is an adjustment for the fanbelt. Under the dynamo is a long slotted bracket. Undo the nut/bolt that fixes the dynamo to the long slotted bracket then the dynamo top (pivot) bolts need to be slightly loosened. This allows the dynamo to pivot on the top bolts . I use a long bar between the block and the dynamo to keep the belt tensioned when doing the bolt back up.

However, a loose fanbelt will not cause lights to flicker - even if you loose the fanbelt altogether the lights will be constant (until they dim and fade as the battery goes flat.
It sounds like a loose connector somewhere

Post by **57traveller** » Wed Oct 22, 2003 8:34 am

Assuming you are still using a dynamo, and the drive belt tension is o.k., have you checked the brushes and commutator in the dynamo?
Similar happened to me some time ago and it turned out to be a stuck carbon brush.

Post by **Kevin** » Wed Oct 22, 2003 11:59 am

Dont forget to check the earthing points they can cause some interesting symptons.

Post by **winger300** » Thu Oct 23, 2003 2:31 pm

It most probably is a dynamo problem, when the car is idling, the headlamps dim noticably. And i've had a flat battery on a number of occasions.

When the battery is flat, the headlights go out altogether when the engine is at idle speed.

Post by **rayofleamington** » Thu Oct 23, 2003 7:09 pm

the headlamps dim noticably

that is normal with a dynamo as they have negligible output at idle.
If they dim down so much they don't light up the road then that may just be a poor battery.

My (new) 1961 4 door has flickering lights too - in fact all all the lights flicker :? But it has an alternator conversion

I'll have to have a good look at it when I get some spare time.

Post by **winger300** » Sat Oct 25, 2003 12:23 pm

I think i have two problems,

one is that i only do short journeys, maybe no more than 10 minutes to Uni/back. So im having to re-charge my battery every week.

When i rev the engine the electric output wavers considerably, sometimes my cd player cuts out. So could this be the sign of a faulty Regulator?

I wasn't going to mention this since you have an alternator, but reading your other post since your alternator is at fault.

Alternatively could my problem be the dynamo brushes? I bought some new ones, but have no idea how to replace them.

Which component should i be looking at first?

Post by **rayofleamington** » Sat Oct 25, 2003 1:15 pm

the cd player cut out may relate to voltage or just to vibrations :?
On short journeys of 10 mins up to 4 times a day you shouldn't need to charge the battery every week, so there is something wrong.

I strongly recommend to check your regulator/dynamo output!
Some of the problems may relate to a poor battery, (or a very weak dynamo) but I also suspect you have a combination of problems.
If you can't get hold of a voltmeter easily, you're free to pop down the road to Leamington this afternoon or Monday / Tuesday evening.

but yes - my flickering lights are most likely down to a rubbish alternator.
When the charging output goes much higher than 14.5 volts the battery life reduces drastically (>15 volts ruins the battery)

Post by **winger300** » Wed Oct 29, 2003 10:26 pm

or of course the problem could be loose wires on the dynamo terminals

Post by **rayofleamington** » Wed Oct 29, 2003 11:01 pm

I take it you found the problem then ?

Post by **winger300** » Sun Nov 30, 2003 11:50 pm

i thought i had solved the problem.

However it seems to still be playing up. I've done two long journeys recently, with wipers/lights/heater on, and at the end of each journey i have had a flat battery.

When the car is moving everything works fine, just when it idles, the wipers stop, lights dim almost to nothing etc.

I suppose this rules out any faults with the dynamo, The ignition light goes out as per normal, but the battery just isn't being charged.

Perhaps its just a duff battery?

Post by **rayofleamington** » Sun Nov 30, 2003 11:57 pm

it may well be a duff battery.
you can have a battery test done - there is a piece of test equipment that draws high current from the battery and monitors the power output.
Or Just charge it then leave the lights on for a while - if it drops quickly then the battery is duff.
Unfortunately it takes a good guess to decide how long you can leave the lights on to get a valid result.

Post by **pskipper** » Mon Dec 01, 2003 11:30 am

My battery is even worse than that

After a whole days charging it had just enough juice to click the fuel pump twice and then died! Hay ho, new battery time

Post by **alainmoran** » Mon Dec 01, 2003 12:06 pm

Most places which sell batteries are highly likely to have a battery-tester on hand, which they will gleefully use on your battery, as it means a likely sale.

They should also have some way of testing your charging circuits, it might not be the battery which is dead, it could be your charging circuit, although if the charging circuit is dead it may very well have taken the battery with it.

Post by **rayofleamington** » Mon Dec 01, 2003 12:47 pm

if the charging circuit is dead it may very well have taken the battery with it.

More likely that's the failure mode of an alternator (not a dynamo) - when they stop regulating correctly the higher charging voltage will damage the battery, blow bulbs, fry relays, etc..
I've had that more than once

People forget to check their car when changing the battery so the new battery gets damaged as well.
From memory Andrew has tested with a Voltmeter anyway so it's not an overcharging issue

Post by **alainmoran** » Mon Dec 01, 2003 1:09 pm

I was thinking more along the lines of if the dynamo isnt pushing ANYTHING out, then the battery may die of premature old age, due to being cycled so often.

But since the output of the dynamo has been checked in isolation to the rest of the system then that's unlikely to be the problem.

Post by **Kevin** » Mon Dec 01, 2003 2:12 pm

After a whole days charging it had just enough juice to click the fuel pump twice

Philip you should buy yourself a hydrometer you would have been able to tell if it was recharging or not, and also the condition when you took it off, it has been known for a jammed starter to convince some that the battery is duff, a hydrometer is very useful and quite cheap to buy.

Post by **brixtonmorris** » Mon Dec 01, 2003 2:21 pm

the car can run without a battery. start it and disconect the battery if charging system is working morris will run without bat

Post by **alainmoran** » Mon Dec 01, 2003 3:24 pm

That's a VERY good way to test the charging circuit ... if it dies when you disconnect the battery then you KNOW that its not charging ... nice and simple, but effective.

Post by **rayofleamington** » Mon Dec 01, 2003 3:39 pm

but don't they normally die at tickover without a battery?