Beta Control Panel with LEDs

[pearley]

My neighbours Beta 75, about 17 years old with twin alternators, has stopped charging the domestic batteries. It has the C type control panel but with LEDs rather than normal warning lamps. The domestic LED doesn't illuminate either with ignition on or if engine running. It still doesn't charge if the engine speed is increased so I'm assuming an alternator fault.

 

However before I start looking as it probably a rats nest of wiring how is the alternator charge circuit arranged?

 

 

Edited February 29 by pearley

[Tony Brooks]

8 minutes ago, pearley said:

My neighbours Beta 75, about 17 years old with twin alternators, has stopped charging the domestic batteries. It has the C type control panel but with LEDs rather than normal warning lamps. The domestic LED doesn't illuminate either with ignition on or if engine running. It still doesn't charge if the engine speed is increased so I'm assuming an alternator fault.

 

However before I start looking as it probably a rats nest of wiring how is the alternator charge circuit arranged?

 

 

 

Not Beta specific.

 

If it were the belt then the LED should still light the moment the ignition is turned on.

 

In an ideal world and assuming a 9 diode alternator, the domestic alternator warning lamp would be fed via a relay that is energised by the same terminal n the switch as the engine warning lamp. After the usual hand and eye checks on connections, possibly fuses, and cables, I would suspect the relay.

 

To add:

 

Still assuming a 9 diode alternator. If you have the ignition on, engine stationary and the take the D+ (warning lamp) connection off the alternator and touch it to clean metal (negative) the lamp should illuminate. if it does, then the chances are the alternator brushes are worn out. Often they come as part of the regulator.

Edited February 29 by Tony Brooks

[pearley]

2 minutes ago, Tony Brooks said:

 

Not Beta specific.

 

If it were the belt then the LED should still light the moment the ignition is turned on.

 

In an ideal world and assuming a 9 diode alternator, the domestic alternator warning lamp would be fed via a relay that is energised by the same terminal n the switch as the engine warning lamp. After the usual hand and eye checks on connections, possibly fuses, and cables, I would suspect the relay.

But I would expect the alternator to self excite when revved and it doesn't. Domestic voltmeter shows definitely not charging.

 

Pouring with rain here so will have to wait before I start looking.

[Tony Brooks]

2 minutes ago, pearley said:

But I would expect the alternator to self excite when revved and it doesn't. Domestic voltmeter shows definitely not charging.

 

Pouring with rain here so will have to wait before I start looking.

 

Nine diode alternators use the current from the warning lamp (or current from the LED plus a bypass resistor) to start energising the rotor field. no warning lamp - no energisation current.

 

See my addition to the above post re testing.

[nicknorman]

The Beta 43 at least, has a relay behind the panel. The ignition switch etc is powered from the starter battery. When it is turned on, it energises the relay which connects the leisure battery + to the alternator D+, via the warning light (and a resistor in parallel). So as a first step I would check that the relay is working properly and connecting the leisure battery + to the warning light when the ign is switched on. If not check the other side of the relay. If no +12v, could be an issue with the multi-way plug because the leisure battery + connection is via the domestic alternator B+ and up through the multi-way connector to the panel. 

 

Presumably the leisure battery isolator switch is on and working properly?

 

Other causes for this issue is basically something else in the circuit from the leisure battery + to the alternator D+ via the relay, the bulb and resistor, the multiway connector and the D+ terminal, or a faulty alternator

 

For fault finding I would start with the easiest things to reach. Having checked for 12v on the warning light, you could move to the D+ terminal on the alternator - if it has +12v on it when the ign is on, the alternator is faulty (brushes worn out etc) but if it is 0v then it is likely the mutli-way connector in the wiring loom.

 

 

So just to clarify (because the above is a bit waffly!) and summarise your question "how is the alternator charge circuit arranged":

 

There is a thinish green/yellow stripe wire from domestic alternator B+ on the engine, via the wiring loom and multiway connector, to a relay behind the panel, to the warning light, back down the wiring loom via the multiway connector as a blue/yellow stripe wire, to the domestic alternator D+. The relay is activated by current from the starter battery when the ignition is switched on.

Edited February 29 by nicknorman

[Tony Brooks]

5 hours ago, nicknorman said:

or fault finding I would start with the easiest things to reach. Having checked for 12v on the warning light, you could move to the D+ terminal on the alternator - if it has +12v on it when the ign is on, the alternator is faulty (brushes worn out etc) but if it is 0v then it is likely the mutli-way connector in the wiring loom.

 

It won't have 12V on it if unless the cable is disconnected and the voltage measured at the end of the cable, not the D+ terminal.

 

With the cable still connected the bulb/LED + resistor form a voltage divider with the rotor with the rotor having far less resistance, so the voltage at the CONNECTED D+ terminal will be far lower then 12V, but I have never measured it - easier to dab the cable to negative and watch the bulb.

[nicknorman]

1 hour ago, Tony Brooks said:

 

It won't have 12V on it if unless the cable is disconnected and the voltage measured at the end of the cable, not the D+ terminal.

 

With the cable still connected the bulb/LED + resistor form a voltage divider with the rotor with the rotor having far less resistance, so the voltage at the CONNECTED D+ terminal will be far lower then 12V, but I have never measured it - easier to dab the cable to negative and watch the bulb.

My point is that if there is +12v on the D+ terminal, it means there is no circuit through the rotor, typically because the brushes are not connecting. If everything is working then the voltage would be around 1v, but then the light would be on. Which it isn’t.

[ditchcrawler]

8 minutes ago, nicknorman said:

My point is that if there is +12v on the D+ terminal, it means there is no circuit through the rotor, typically because the brushes are not connecting. If everything is working then the voltage would be around 1v, but then the light would be on. Which it isn’t.

Zero and no light could indicate a bust wire, inline plug/socket 

[Tony Brooks]

23 minutes ago, nicknorman said:

My point is that if there is +12v on the D+ terminal, it means there is no circuit through the rotor, typically because the brushes are not connecting. If everything is working then the voltage would be around 1v, but then the light would be on. Which it isn’t.

agreed

[Tracy D'arth]

The multiplugs ( possibly 2 pairs ) in the loom are a trouble point.

The resistors in the display panel for the warning lights are known to go open circuit which will stop the alternator energising.

[nicknorman]

14 minutes ago, Tracy D'arth said:

The multiplugs ( possibly 2 pairs ) in the loom are a trouble point.

The resistors in the display panel for the warning lights are known to go open circuit which will stop the alternator energising.

However, if the fault were the resistor open circuit, the light would be on.

[ditchcrawler]

I would wiggle the plugs first

[pearley]

Thanks, I well aware of the problems with the multiplug and had already suggested the owner look at them.