Alternator issues??

Crazylurcher · Sep 28, 2012

Hi guys, just bought a 1966 sII and I ve noticed a red light in the bottom left corner of the dash that gets brighter the higher the engine revs.

After looking under the bonnet I found that the fan belt was loose and so I tightened it confident that this would solve the problem. As it turns out its helped a little but not solved the problem, the belt has about 15mm free play in it now and I m loathed to tighten it anymore,

Thoughts?

dominicbeesley · Sep 28, 2012

With engine off check to see if you can move the fan round by hand (i.e. check for slip) you may have oil or anti-freeze on the belt. I've managed to "rejuvinate" contiminated belts in the past by rinsing off with brake cleaner or carb cleaner.

Is the battery ok?

Then check and double check wires to alternator and grounding. If wires are loose or corroded the light will glow and your battery won't properly charge, also check they've not rubbed through where they are routed round the block.

After checking all that and being satisfied its time to start suspecting alternator could be brushes, knackered regulator, etc...

Crazylurcher · Sep 28, 2012

Battery and belt both seem fine and there dosnt seem to be any contamination or slippage. What would make the light brighter as the engine revs higher?

dominicbeesley · Sep 28, 2012

If the regulator is dead or dying it can cause overvolts which I beleive causes this symptom (and will not do yer battery any good). I've not had it happen to me before though so can't confirm.

I'd triple check the wiring first though..it could be a connection the comes more loose as you vibrate it more.

I got a new alternator from Woods Auto Electrics in Huddersfield for a reasonable price

Just noticed though that yours is a S2...didn't they have a dynamo rather than an alternator?!?

Crazylurcher · Sep 28, 2012

I m not really sure to be honest, I would love to change it back to a dynamo if that were possible

I m going to get a voltmeter on the battery tommorow

pobby · Sep 29, 2012

You need a volt meter across the battery
With the engine running What your looking for is ;

13.8 - 14.2 volt is perfect charge rate
13.5 - 13.8 volt is except able charge rate
13.0 - 13.5 volt is putting out enough charge to keep everything going but not really enough to recharge battery properly
Below 13 volt the alternater isn't putting out enough and need changing

If you get more than 14.5 volt then the alternater is over charging and will boil the battery

It's hard to test an old battery with our special equipment like a drop tester do it's best to try and think how old it may be. Normal life of a battery is between 3 and 5 years but that dosnt mean an old battery is no good it's just a guess

Run the test and see what you get but it sounds to me you probally need an alternater

Crazylurcher · Oct 2, 2012

pobby said:
You need a volt meter across the battery
With the engine running What your looking for is ;

13.8 - 14.2 volt is perfect charge rate
13.5 - 13.8 volt is except able charge rate
13.0 - 13.5 volt is putting out enough charge to keep everything going but not really enough to recharge battery properly
Below 13 volt the alternater isn't putting out enough and need changing

If you get more than 14.5 volt then the alternater is over charging and will boil the battery

It's hard to test an old battery with our special equipment like a drop tester do it's best to try and think how old it may be. Normal life of a battery is between 3 and 5 years but that dosnt mean an old battery is no good it's just a guess

Run the test and see what you get but it sounds to me you probally need an alternater

So did the test today and battery without engine running was 12.5 without the engine running, with the engine idling over it picked up to 13 volts, with some revs applied it slowly rose to 14.4, light is on pretty much constantly now

Oldseadog · Oct 2, 2012

It certainly sounds like a bad earth. The slow rise up to 14.4V and the light staying on supports this.

Check that every earth is sound, even if you have to disconnect them (best way!) and make them off again.

Clean them thoroughly with a soft wire brush and smear with vaseline before reassembling them.

Even though they may initially feel quite tight, all it takes is a build up of corrosion to reduce the efficiency of the circuit.

Crazylurcher · Oct 2, 2012

Oldseadog said:
It certainly sounds like a bad earth. The slow rise up to 14.4V and the light staying on supports this.

Check that every earth is sound, even if you have to disconnect them (best way!) and make them off again.

Clean them thoroughly with a soft wire brush and smear with vaseline before reassembling them.

Even though they may initially feel quite tight, all it takes is a build up of corrosion to reduce the efficiency of the circuit.

I d never thought of the earths, I ll make that my tomorrow job and let you know how I get on, is it just the alternator earth?

Oldseadog · Oct 2, 2012

All the earths could do with a good check ... battery to engine, chassis to engine, engine to alternator, chassis to body, engine to body.

If you have a good multimeter, you should get no more than 2 Ohms between any of them, as you are ideally looking for a dead short throughout.

It can be a bit of a ball ache, but it's well worth doing.

Crazylurcher · Oct 2, 2012

Fingers crossed it solves the problem, just an apparent oil pressure problem to sort at some point and I ll have a dash free of warning lights

Alternator issues??

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dominicbeesley

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pobby

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