R100GS PD charging light not lighting up.

[bubbles]

My 1991 GS appears to have a charging fault, it has Thunderchild diode board which has been fitted for probably 20 years, and I’m struggling to understand what the voltage regulator looks like. The Haynes wiring diagram shows the voltage regulator with 4 wires, 3 connections D+, D-,DF but I’m unable to find that on my bike. I have taken the instrument panel apart and checked the charging lamp and that’s ok. I understand the charging system on my 1978 80/7 and have changed the voltage regulator, alternator, rotor, stator and diode board on that in the past but I’m at a loss to know where to start on the GS, any help would be appreciated.

 

[Stirlingmoz]

The regulator is usually under the tank on the right side of the frame behind the headstock.

Once you’ve located it, a quick check you can do to determine if it is the voltage regulator or alternator system giving you problems is to remove the plug from the voltage regulator. Jump the blue and black wire and start the bike up. If the charge light goes out, you have an issue with the regulator. If the charge light stays on, the problem is likely in the alternator or diode board.

Alternator brushes are also worth checking

 

[bubbles]

The regulator is usually under the tank on the right side of the frame behind the headstock.

Once you’ve located it, a quick check you can do to determine if it is the voltage regulator or alternator system giving you problems is to remove the plug from the voltage regulator. Jump the blue and black wire and start the bike up. If the charge light goes out, you have an issue with the regulator. If the charge light stays on, the problem is likely in the alternator or diode board.

Alternator brushes are also worth checking

Yep that’s where it is on my 80/7 but can’t find anything that looks like the voltage regulator on the GS?

 

[mikeyboy]

I’m not familiar with the thunderchild rectifier,
Can you post a photo or two of it along with the wiring connectors?

 

[bubbles]

I’m not familiar with the thunderchild rectifier,
Can you post a photo or two of it along with the wiring connectors?

Thanks for your interest, will see what I can do tomorrow.

 

[Stirlingmoz]

Nothing similar to this red oblong ‘Wherle’ regulator ?

(Picture is of my old monolever while testing the beancan)

 

[bubbles]

Nothing similar to this red oblong ‘Wherle’ regulator ?

(Picture is of my old monolever while testing the beancan)

View attachment 511213

That’s exactly what I was looking for, but can’t find.

 

[bubbles]

General view of the right had side of frame

This is the side of the lower item in the first picture

 

[DrFarkoff]

This is the side of the lower item in the first picture

If that plugs into the Grey bit with the two big Phillips head screws ?

That should solve your problem !!




Aluminium Bit is the Ignition Amplifier

Grey Bit I suspect is an aftermarket regulator

Black Block is Indicator relay including hazard / 4 way Flashers

 

[bubbles]

The connections of the above item.
O

 

[bubbles]

If that plugs into the Grey bit with the two big Phillips head screws ?

That should solve your problem !!


View attachment 511253

As you can see it has multiple connections.

 

[bubbles]

Is this the voltage regulator?

 

[bubbles]

The Thunderchild diode board.

 

[DrFarkoff]

@bubbles

 

[DrFarkoff]

View attachment 511254View attachment 511255
Is this the voltage regulator?

No See above

That is the Ignition amplifier

 

[bubbles]

@bubbles

View attachment 511259

Thanks for your reply but that has too many connections to be the voltage regulator?

 

[DrFarkoff]

Thanks for your reply but that has too many connections to be the voltage regulator?

Is this photo from your GS ???

I suspect that it is! As that is a GS type Crashbar mounted oil cooler



@bubbles .......... I think I get it now !!

The "Grey" bit with 2 screws is actually the Indicator module !!

That connector that I highlighted earlier should plug into the regulator

What is attached to those 2 darker coloured screws facing forwards, below the shiny phillips ??

If it is a bit of black plastic The reg may have simply fallen off and unplugged the connector and fallen off

 

[mikeyboy]

I suspect the thunderchild rectifier does not have a separate voltage regulator,
Edit,,
Hmm
Looking at the wiring diagram shown above ,it would appear that the TC rectifier uses standard connections,
Is there more to the installation instructions ?
I find it hard to believe that the regulator has fallen off?
And the system,presumably was working ok until recently?

 

[Stirlingmoz]

The photo of the plug that @DrFarkoff posted and circled is definitely the one that normally plugs into the regulator.

Could the source of the charging fault you mention in the original post be because the regulator has 'left the building' ?

If the plug is hanging loose, the regulator may also have been hanging loose and has somehow become detached ?

 

[DrFarkoff]

@bubbles

Use a length of wire and GROUND the Blue wire with the ignition on

Your ignition light should light up

That's where the regulator should be "OR" Wherever that will reach to ??

Mine is a pre 1991 R100GS so don;t have everything in the same place but the Loom colours are all the same