charging problem ...

bodger · Post by **bodger** » Tue Apr 14, 2015 7:24 pm

Please , any ideas ...?
Came back from holiday to find my battery flat ..
I checked the alternator output via multimeter on the battery terminal on the rear of the alternator and its .. going from about 14 volts and dropping off to 1 , 2 or even zero and then back up again ...
Ive changed to rectifier set and it still does it ...
But the thing that puzzled me is ... i took the sense wire off the alternator and with ignition on i get a steady 11 to 12 volts but with the engine running and the small wire then voltage fluctuates from almost zero to 12 +volts ?
Please help

ChrisJC · Post by **ChrisJC** » Tue Apr 14, 2015 7:47 pm

Never go on holiday!!

Maybe you need new brushes.

Chris.

bodger · Post by **bodger** » Tue Apr 14, 2015 7:53 pm

Lol ...
Hi chris

The strange thing is i cant get my head round is the voltage going up and down on the sense wire ... ?

mike-b · Post by **mike-b** » Tue Apr 14, 2015 9:25 pm

Certainly sounds like an alternator fault, however the sense wire should be live (12V) or close to it with the ignition on, this is best checked disconnected from the alternator.
if 12V is found (ignition on engine not running) try earthing the sense wire - your ignition light should now be on. if so that part of the system can now be deemed as OK.
Having ruled that out - you say you have changed the rectifiers - I would be looking at changing the voltage regulator, but firstly I would check the brushes. If its a Bosch alternator the brushes & regulator are "as one" unit..
What is the engine to Negative connection like? To prove that point I would use one half of a jump lead clipped to the alternator and the battery neg.
Note also if it is a Bosch alternator the brushes can be quite long but still not work properly, I have had that problem and it was a sod to find because they looked good and long enough.
Hope that helps.

bodger · Post by **bodger** » Tue Apr 14, 2015 11:02 pm

Thankyou Mike.
The sense wire when disconnected from the alternator and the ignition switched on shows approx 12v
But its left disconnected from the alternator and now with the engine running the voltage fluctuates between 2 volts and 12 volts approx

bodger · Post by **bodger** » Wed Apr 15, 2015 2:15 pm

Update ...
rewired the charge light ... alternator back to instrument panel
fitted new regulator
redid earth chassis to engine connection .......

Still voltage going up and down at alternator/ battery terminal
ie: 14 v to 1v (approx ) ..up and down

DaveEFI · Post by **DaveEFI** » Wed Apr 15, 2015 2:42 pm

99% of problems with alternators (assuming connections are ok) are cured by a new regulator.

Not come across a fault like your which wasn't.

bodger · Post by **bodger** » Wed Apr 15, 2015 2:58 pm

New regulator and rectifier set fitted and it still does the same as it did before i fitted them ..
all connections are fine , ive even rewired the charge light / sense wire
and earth connection to engine

mike-b · Post by **mike-b** » Wed Apr 15, 2015 2:59 pm

The sense wire from the ignition switch should be live when the ignition is on, it is there for a purpose. That feed from your Ign switch is there to "Excite" the alternator when the alternator is running slowly - say at tick over. As the speed of the alternator increases the alternator can then "Self excite" and it puts a feed along your sense wire to your Ign light.
The Ign light now has a Pos feed to both sides, one from your Ign switch the other the alternator. Electrically a "bulb" with a feed to both connection will not glow, in other words it goes out because it has not got a negative so there is no circuit. All it does is confirm the alternator is "Self exciting" and must be producing an output from its exciting circuit.
That does not mean the main output is good though as the exciting circuit has its own rectifiers though they are part of the rectifier pack.
I would open the alternator and check the 3 windings at their ends NOT through the rectifiers. If a winding has gone open circuit it will play havoc with your charging system.
Also check the rectifier & winding connection are good.
Check your windings using continuity and then check what resistance each winding has.
They should be about the same - not exactly - but near enough to say they are very close.
You say you changed the rectifier pack, so if the windings are good likewise the rectifiers you only have the regulator & brushes left.
The alternator will not work properly without that sense wire connected.
What make of alternator are you using?

bodger · Post by **bodger** » Wed Apr 15, 2015 4:14 pm

Hi mike , the alternator is a bosch 0 124 415 002 ..100A

When i took the rectifier set off the other day waiting for the new one to arrive
i checked the windings then ...

there is no continuity to earth on them and there is good continuity across the pairs

i then fitted the new set ...

This morning the new regulator/ brushes arrived and is now fitted ...

there is no differance as there was before i fitted the new parts

mike-b · Post by **mike-b** » Wed Apr 15, 2015 8:02 pm

You say there is no difference now you have fitted new rectifiers, regulator & brushes.
After that lot the only thing left is the windings and you have checked them as well.
I don`t consider you an idiot ( we all make stupid mistakes - me included ) you are sure all the connections are in the correct place?
If I was in your position now I would be looking at the cars wiring especially the neg returns to battery, even to the point of fitting a temp return from the alternator to the battery neg.
Without the sense wire connected to the alternator the output will fluctuate from very low to 12V or thereabouts, the alternator must have that connection.
Have you changed the ignition light bulb? It does make a difference, any old 12v bulb will not do, it needs to be at or close to 1.2 to 2.2 watts.
When you stated what alternator you had I done a check on Google and found your alternator type. These things are cheaper than chips, £29.99 Yes 29.99..
Without looking at the car wiring I can`t do a lot from here - you have checked everything and / or replaced it.
If it helps at all ........ try this www.megavaux.co.uk. at the top of the page near the `phone number you can do a search. input this part no. 9195753 at 29.99 its a bargain and a spare plus it could prove a point - alternator or car wiring fault.
Let me know what you find, I really want to know what this problem is.
regards, Mike.

bodger · Post by **bodger** » Wed Apr 15, 2015 9:30 pm

Hi mike , im thinking it must be the vehicle wiring now ... wish id saved the £70 ive just spent on the regulator and the rectifier ...aaagghhh
The sense wire voltage when disconected from the alternator fluctuates too ... with the engine running ... stable with just the ignition on though ...
Got me well puzzled now .

Can i run a clean battery 12v feed straight to the alternator small terminal ..or will that damage the alternator ?

Spongo · Post by **Spongo** » Thu Apr 16, 2015 8:20 am

Could it be the battery itself has gone duff in multiple cells and that is what is causing the issue?

Is there electrolyte in the cells?

DaveEFI · Post by **DaveEFI** » Thu Apr 16, 2015 8:50 am

As a matter of interest, has the alternator done a vast mileage?

bodger · Post by **bodger** » Thu Apr 16, 2015 8:56 am

Spongo wrote:Could it be the battery itself has gone duff in multiple cells and that is what is causing the issue?

Is there electrolyte in the cells?

Stange thing is the battery has recovered since it went flat ( see first post )
And it seems to be charing fine ..even though the alternator output is fluctuating ...
Yes ive tried 2 differant multimeters