C123 230E Battery drain and charging problems

[Gizzardio]

Hi All

I have a C123 230E and battery was totally dead after I last drove it. I replaced it with new and then this also drained overnight so obviously there's some parasitic discharging going on with the ignition off.

Also I noticed that my dummy warning lamps do not illuminate when key is set to run position before start.


I've trawled through the forums and tried to collate all the tests recommended and the results here.

1) Test voltage across battery with engine running

12.5V - would expect 13.5 -14V here so not charging as it should.


2) Test voltage at blue wire at alternator with ignition on. Should be ~2V with warning lamps illuminated. Check also with engine running. Should be ~12V

With ignition on and connected plug, this is 10.5V without engine running. With ignition off and connected plug it remains 10.5V.
With disconnected plug, ignition on it reads 12V and with ignition off read zero.
Also above check with ground to both alternator casing and earth point.
The live + twin red wires at alternator read 12V whether ignition is on or off.

3) With ignition on, jiggle the alternator, connection plug etc to see if warning lights come on

No change


4) Check fuse 12 and voltage at either side to ground. Remove fuse 12 and check for 12V at blue wire at alternator connector or not

Either side of fuse read 12V with fuse in. Just live side read 12V with fuse out as you would expect.
Fuse still removed, no voltage at the blue wire with disconnected plug and ignition off. 10.5V at blue wire with plug connected and ignition off.


5) Check resistance / continuity of D+ (blue wire connector) through alternator, i.e. to ground

Reads 997ohms


6) Check voltage at blue wire at alternator with ignition off. Should be no voltage at all. Key on should get slightly less than battery voltage and warning lamps turned on in dashboard.

Ignition off reads 10.5V to ground. Resistance reads 538ohms between either red wire terminal and the blue wire terminal.


7) Check resistance between blue wire (with unplugged from alternator) and negative terminal of battery

Unplugged from and plugged to alternator shows infinity ohms.


8) Alternator diode test. Disconnect live + to battery. Set multimeter to diode test. Place red lead from multimeter on casing of alternator and black on post that + live was connected to. Should read about 500-800mV. Reverse the leads and should read 1 or out of range

Unplugged and using alternator terminals only. First with red lead to casing and black to + red wire terminals reads 660. Also the case for the blue wire terminal.

When reversed, red wire terminals both show 1 (out of range) but blue shows 1158. I THINK THIS IS ONE OF THE KEY TESTS HERE AS SEEMS LIKE DIODE FAILURE IN REGULATOR AT LEAST.


9) Test volt drop from alternator with black lead on + live to battery live and red lead on battery + post. Should be less than 0.2V. Can do same test for earth / ground to alternator.

Plugged to alternator, with ignition off. Was about 0.04V drop for red wire terminals and 0.9V drop for blue wire terminal. Shouldn't be any volt drop at blue wire with ignition off I would've thought as should be open circuit?


I didn't do the AC voltage test yet as I couldn't start the car after the testing and had to recharge my jump kit.


So my conclusions from above is that I at least have a problem with alternator not charging, diodes allowing current to flow from battery into alternator and out of the blue terminal to ground and wiring seems OK so far. Might not be the full story but IMO these items have to be rectified before more testing.

What you think?

 

[optimusprime]

Just take 2 screws out of the alternator regulator ,, replace the regulator with new one this is your problem ,,,but only if the charging light bulb is lit up in the console If bulb is not lit then the bulb will need replacing ...the bulb is the fuse for the alternator charge citcuit..

 

[Ted]

It’s very simple to test these.
With ignition on and engine not running, disconnect the plug.
Charge warning light should be off.
Ground the blue wire. Charge warning light should be on full brightness.
The charge warning light should work as above as it provides initial excitation for the rotor.
Check you have a good 12 volts on the red wires. I prefer to use a test light.
If the above checks out, and the fan belt is ok and rotating with the engine running, the alternator is faulty.
As @optimusprime says, it’s probably easiest/cheapest to replace the regulator on the back as this is the most likely part to fail, plust you get a set of brushes into the deal as part of the regulator.

 

[Gizzardio]

Thanks I will try the above then replace the regulator as it's a cheap and simple fix like you've both suggested.

If I ground the blue wire and the charge warning bulb doesn't illuminate then it could be the bulb has blown or something else is going on

 

[Ted]

Most likely the bulb. You need this working for it to charge properly.

 

[Gizzardio]

Hmmmmm. Please more guidance needed!

I've fitted the new voltage regulator. I cleaned the ground contact as advised above whilst I was there and checked the slip ring that seemed ok in my limited experience.

But didn't fix the issue. Still showing 11.9V at blue wire with ignition off. Also, and probably as a result, I'm not getting any warning lights showing on ignition on position.

Additional tests done now:

10) Removed battery indicator bulb from binnacle, tested, and shows 100Ohms through so that's OK.

11) With the bulb removed, I re-rested the blue wire, ignition OFF, and still showing 11.9V. Battery is 12.6V at terminals.


As someone said, the bulb is the fuse for the blue wire, so if that's the case, then with it removed, there should be no voltage at blue wire.

Then the above leads me to suspect that the only way any voltage could be showing at blue wire is leaking from the +ve red wires at the alternator, through the alternator itself.

One thing I forgot to mention before - When this problem first arose I did notice a burning smell from the engine bay after I'd been out. Could it be that the alternator innards are shredded and causing a connection between battery +ve and the blue wire? My understanding is that there should be no connection and that the blue wire created the necessary magnetic field that the +ve side spins around in order to create it's 14V or so output voltage back to the battery.

 

[Ted]

The warning light provides the initial excitation via the blue wire.
As per previous post, with ignition on but engine not running, remove the plug and ground the blue wire. If the warning light comes on then that circuit is good.
You don’t need to check for any voltage on the terminal the blue wire goes to on the alternator. If you aren’t happy grounding the blue wire, ground it via a test light. That will limit any current flow and the warning light should glow dimly.
Assuming you have a good 12v to the red wires that is all you need to test.
It’s possible that one (or more) of the rectifier diodes has blown but you can only test this with the alternator removed and dismantled.

 

[Gizzardio]

I have grounded the blue wire before with plug removed, and the warning lights didn't come on.

I have found a local alternator testing and reconditioning place who offer full bench testing so I'll take it down there and eliminate the doubt surrounding that too.

 

[Ted]

If the light didn’t come on (ignition on, engine not running) then you need to check it out. Most likely the bulb but you say you have tested that - might be worth substituting it.
As this provides the initial excitation, you will find that it doesn’t charge unless revved right up. It should then charge as normal.

 

[Gizzardio]

So here's the answer...

It was my alternator rectifier diodes failing plus a loose wire around the stator. I did think in my first post it was something to do with leaking current back through and seemingly the B+ side making the D+ side constant live even without ignition.

Had a new rectifier fitted and replace rotor, and refitted to car. All warning lights display as expected on ignition then turn off on running. Tested output and showing 14.1V at battery so charging seems within range.

Thanks for all help. Hope someone else finds this useful in the future too

 

[alabbasi]

I've not read everything but have you tried pulling fuses? if the battery drains overnight you have a short on a circuit. You can connect a test light between the battery and the terminal and if the light is on, pull fuses with the ignition off until the light goes out and you'll know which circuit has the short.