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BN4 Generator Woes

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prutland

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After a very wet journey - low beam lights and wipers, I pulled up into my driveway and turned the motor off to open the garage doors. The car wouldn't restart - flat battery. It appears that the generator either wasn't charging at all, or wasn't charging sufficient to overcome the electrical load from headlights and wipers.

I have removed the generator and checked brushes, cleaned the commutator etc. Also confirmed that the generator works as a motor (as per Moss YouTube video).
I also found an online version of a Lucas Generator and Control Box testing handbook and have also carried out a couple of the recommended tests with the generator reinstalled.

I am trying to better understand the test results and I am hoping that someone out there may have some insights:

Test 1: Generator disconnected, voltmeter reading from "D" terminal to earth.
This showed 0.8V at 750 rpm and 2.0V at 2000 rpm (3000 rpm at generator). Based on my reading of the testing handbook, this is as expected and shows that the armature and brush connections are OK.

Test 2: Similar to above but with "D" and "F" connected. Voltmeter reading from "D" terminal to earth.
This showed 9V at 800rpm and 16V at 1100rpm. Again, based on my reading of the testing handbook, this is as expected and shows that the generator is operating OK.

Have also tested continuity from generator to control box and that shows full continuity of the wiring.

Other testing:
Resistance "D" terminal to "F" terminal: 8 ohms
Resistance "D" terminal to ground: 6.7 ohms
Resistance "F" terminal to ground 1.9 ohms

Do any of these results look odd? I still need to check the control box but I am trying to confirm that nothing in the generator testing indicates an issue?

Paul R
Melbourne
 
Paul-I had a similar problem and it turn out to be the ground connection on the Regulator. The ground connection was loose and therefore the regulator did not charge the battery.

If the ground is good check cut in and cut out at the regulator. I believe a VOM is all you will need to check the charging settings of the regulator. Peter
 
On your last trip, did you happen to notice if the 'IGN' light on the tach was glowing? If so, you were running off the battery and the charging system is likely the problem; if not, it could be the battery (though they most often fail when starting). I'd check the battery with a load tester before I went into the charging system.
 
Thanks both,

I did some more diagnostics today. Adjusted the regulator voltage to be closer to spec, but didn't have the opportunity to check the cut in / cut out, that will be a job for another day'(next weekend!). I am also going through cleaning all the control box wiring connections. Ground appeared to be OK, but time will tell once I have finished with the cut in / cut out.

With regards to the IGN light, I must admit that I didn't notice. It is usually hidden behind the steering wheel spokes, but I strongly suspect that it was lit. I have just installed some LED bulbs for the instrument lights so the IGN light is actually visible in daylight, so I have no excuse!

Battery likewise seems to be OK. It certainly started the car OK a number of times throughout the day, including first thing in the morning when everything was cold.

I will report back in due course.
 
What's the condition of the starter motor? You indicated that when everything was cooled down, the car started OKay. Did you confirm dead battery condition? Before switching to a high torque starter unit, my original would not engage and turn the engine over under certain hot conditions. The "no start" situation could also be attributed to a dead cell in the battery.
 
Thanks gonzo,

A problem with the starter motor was not something that sprang immediately to mind, but is a possibility given the drowning it must have received on the journey.

I recall hearing the starter solenoid when trying to start the car, but (perhaps wrongly) assumed that the battery must have been nearly flat. The starter does occasionally stumble when starting , usually a pause between pressing the starter and the starter motor starting to turn the motor over - usually when cold.

I guess I will see what I discover with the cut in / cut out. If that draws a blank then perhaps the starter motor will be the next thing to investigate. Hopefully not an intermittent fault which would be more of a challenge to find!
 
The field coils in starters--generators too, I think--are wrapped in a cloth-like insulator material. This can degrade over the years and cause intermittency, esp. when hot. There are a few shops around in the 'States that can rebuild them; presumably you have some in Oz too.
 
I have now tested the cut in / cut out and all appears to be in order. The cut in / cut out voltages both appear to be to spec. The generator light goes out at around 900 rpm, and doesn't come on with headlights on or similar
This doesn't give me much of a clue as to what was going on. Potentially pulling the generator out, cleaning all contacts, checking all wiring connections and adjusting the regulator voltage may have fixed what was wrong, or possibly everything was wet from the rain and something decided not to work.
I took the car out for a run today and it performed faultlessly, even temperatures of 5 degrees Celsius didn't affect starting. It will be a watching brief going forwards to see if the issue recurs.
I did learn something about checking and adjusting a control box so not all was wasted.
 
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