Alternator Woes ...

[larsen_huw]

Right .... i don't do electronics well ... and there's a few people here who seem to know a lot more about electronics than me ... so:

Why the F@$k won't my alternator charge up the battery properly. I know the alternator works ... as it does intermitantly charge the battery. I've checked the physical side of things ... fan belt is properly tensioned and i've re-crimped the spade connectors on the alternator.

Anyone got any suggestions for what to try next?

The car's a 1982 Ford Capri ... left the factory as a 1.6L .... now a 2.1L ....

http://www.evecapri.freeserve.co.uk/Huw1.jpg

http://www.colinluck.btinternet.co.uk/Huws_Capri.JPG

You can just see the alternator behind the left side of the radiator.

[rivolette]

Hey look who's asking for help! If you don't know the solution, there's no hope for the rest of us. lol.

1) I'd check the regulator. It's most likely on the "inside" of your alternator. A lot of 'em back in the 80's were embedded. Charging the battery "occasionally" is not a guarantee that the alternator is healthy.

2) Do a load test on the battery. How old is it? It is possible that it's starting to take charge intermittently.

That's a start. We can eliminate some more possible causes when I get back from work! (Or whenever you eliminate the two above...)

[larsen_huw]

I think i can eliminate the battery ... it's only 9 months old, and came with a 4 year gaurentee .... I've charged it up overnight and it seems fine now ... I don't have a multimeter or any electrical equipment, so can't do a load test right now.

The Haynes book of lies (DIY maintence manual) mentions something about a charging regulator ... and in a really crappy sketch, shows it to be located somewhere it blatently isn't! :)

[rivolette]

Your regulator is very likely embedded in the alt. And try and get your hands on a battery load tester. It's the only sure way to find out. Sometimes it's possible for a defective battery to roll off the mill.

A lot of mechanics do that load test for free BTW.

[larsen_huw]

OK ... cheers for the tip.

Got my MOT on Saturday .... will ask if they'd mind doing one then. :)

When your car only has 4 fuses in, it doesn't use much electrical power! :D

[boss]

First of all, charging system consists of three items.

1/ altenator
2/ battery
3/ Warning light

1/ First of all buy yourself a hydrometer ( you spoke of having the battery tested on sat, you cant test a battery with a heavy discharge tester unless the battery is fully charged.)

2/ open battery top and fill hydrometer and compare readings of the six cells, make sure the battery has reasnoble life in it before carrying this test,

3/ if all cells rise a little on reading level then it means that battery is discharged, if all rise into the white or green then its good.

4/ if any 1 or 2 cells differ from the rest then your battery is defective.

Now to the alternator.

1/ remove the connector block from the back of the alternator and use a jumper wire into the thick red wire in the connector block, quickly strike the other bare end against the alternator to see if you get an arc, if yes good if not check the earthing of the alternator against the engine block and check your red wire back to the battery +.

2/ check to see if red alternator warning lamp comes on dash when ign is on, if yes good but if not place a jumper wire into the small wire on the connector block at the rear of the alternator i think the wire is blue, and connect the other end to a suitable earth eg engine block, check to see if light illuminates, if so then alternator needs new brushes or new regulator.

4/ how to check if the alternator is charging without ammeter after making sure that all the above is good. run engine and switch on headlights and blower motor, hold revs at @ 2000 rpm and disconnect battery negative, if engine still running good but if not it means that the alternator cannot charge the blower and headlights and energise the coil let alone put something back into the battery this indicates that therse a faulty diode in the regulator, putting ac into the battery instead of dc, you cannot store AC current.

Alternator cannot charge without having a magnetic field present, there are two ways of doing this,

1/ by using a bulb ( dash warning light) to draw current through the alternator primary circuit which all cars are designed for or the alternator can self excite after you rev the engine over 3200rpm even without a bulb connected.

I hope this is of use, i have rebiult my fare share of alternators and sterters.

[larsen_huw]

Wow.

Plenty of good info here.

I'll take it a bit at a time.

...

1/ First of all buy yourself a hydrometer ( you spoke of having the battery tested on sat, you cant test a battery with a heavy discharge tester unless the battery is fully charged.)

2/ open battery top and fill hydrometer and compare readings of the six cells, make sure the battery has reasnoble life in it before carrying this test,

3/ if all cells rise a little on reading level then it means that battery is discharged, if all rise into the white or green then its good.

4/ if any 1 or 2 cells differ from the rest then your battery is defective.

I topped up the water levels with Deionized water and trickle charged the battery overnight ... starter motor now leaps into life rather than barely turning the engine over! :)



... Now to the alternator.

1/ remove the connector block from the back of the alternator and use a jumper wire into the thick red wire in the connector block, quickly strike the other bare end against the alternator to see if you get an arc, if yes good if not check the earthing of the alternator against the engine block and check your red wire back to the battery +.

Oh yes! It does! :D Was getting sloppy yesterday as i was getting more and more frustrated with it .... twice after firing it up to check if it was charging i forgot to disconnect the battery before fiddling with the leads ... twice i got the shock of my life (luckily not literally! :) ).

... 2/ check to see if red alternator warning lamp comes on dash when ign is on, if yes good but if not place a jumper wire into the small wire on the connector block at the rear of the alternator i think the wire is blue, and connect the other end to a suitable earth eg engine block, check to see if light illuminates, if so then alternator needs new brushes or new regulator.

Yes, the wire is blue ... and the warning light did come on before i started playing with it yesterday ... will have to check to see if it still does ...

... 4/ how to check if the alternator is charging without ammeter after making sure that all the above is good. run engine and switch on headlights and blower motor, hold revs at @ 2000 rpm and disconnect battery negative, if engine still running good but if not it means that the alternator cannot charge the blower and headlights and energise the coil let alone put something back into the battery this indicates that therse a faulty diode in the regulator, putting ac into the battery instead of dc, you cannot store AC current.

I have one of the Capri optional extras of a non-working heater motor! :) I'll use the lights on full beam and the rear window heater.


... Alternator cannot charge without having a magnetic field present, there are two ways of doing this,

1/ by using a bulb ( dash warning light) to draw current through the alternator primary circuit which all cars are designed for or the alternator can self excite after you rev the engine over 3200rpm even without a bulb connected.

I hope this is of use, i have rebiult my fare share of alternators and sterters.

So if i understand you correctly the alternator should charge the battery at over 3200rpm even if the warning light on the dash is blown? The problem has always occured at both above and below 3200rpm.


Thanks for all that great info. I'll try your suggestions tomorrow and see what happens and let you know.

[tich]

Hope you are doing ok with all this but to clarify I would say the fault is either a faulty battery, a faulty alternator (or part of), a current drain, or even a fualty starter motor.

Whilst the previous info is good I would suggest buying a cheap volt meter (about £10 upwards) for more precise info on what is going in and coming out of battery and alternator. Technically you cannot properly test an alternator with a voltmeter but in the real world if it is achieving correct voltage at correct time then the readings are good enough. You need to be getting a charge of between 13.00 volts at just over tickover with all electrics on and a maximum 14.50 volts with no electrics on at high revs (say 3500 rpm). Test this at the alternator and at the battery and compare. I will make comments if you can get figures.

To test battery practically, fully charge battery and leave standing for 24 hours before connecting to car and then see how it performs. Or if cant wait 24 hours then put on car when fully charged but switch on headlamps for 20 -30 secondds (full beam) before starting car. Turn off lights and wait 2 mins before starting though. If battery copes with this it is ok; if not it is suspect especially if new. Or take voltage reading when charged and stood for a few hours. Reading should be between 12.40 v and 12.60 v.

To test for a drain with battery on car, disconnect earth lead overnight. Re connect just before starting and see what happens.

Loads more info but plow through this lot first and make comments?

[boss]

If you really want to get to the nitty gritty, get hold of that cheap ammeter (10) put blach lead in common and red into the 10A hole, disconnect battery negative arnd connect red ammeter lead to batt neg cable with croc clip or vice grip and connect the ammeter black to the batt neg pole, make sure that these do not touch each other, it wont cause a short but it will cause wrong readings.

DO NOT TURN IGN ON!!!!!!!!!!!!!!!!!!!!!!!!

turn you ammeter to the 10A setting and turn sidelights on you will see a reading of up to 2amps, now turn the sidelights off and lock the car and go away for exactly 5min, come back and check to see what the reading is:

0.00-0.02= good
0.00-0.10= will take 4 days to drain battery without use.prob radio not wired through ign like it should be.
0.00-0.18= this is the current needed to energise a relay check to see that a relay is not energised.
0.00-0.50= this is the current that a small 5wbulb takes, check to see that a boot ligh is not staying on or a door light or an underbonnet light.
Anything higher than 0.50 will drain battery in 12 hours.

If there is a discharge disconnect one thing at a time and keep checking the ammeter reading to see of reading has gone back to zero.

[larsen_huw]

Right.

It's been a busy couple of days .... haven't had time to do anything to the car other than cain the nuts off it on the way to work and back! :)

Right .... red warning light on dash is dead .... it doesn't come on at any point ... even when the ammeter is telling me the battery is discharging. Haven't had a chance to earth the blue wire in the back of the alternator though, so don't know if it's a dead bulb or a duff circuit.