Club 80-90 Forums

Had a bit of a prob with leisure batt charging, but oldiebutgoodie gave some good advice but now a bit puzzled. He said the warning light couldn't be an LED and all the batteries would not charge unless a warning light was working and in circuit. What he said makes absolute sense. BUT the 'blown' bulb I took out about three years ago was an LED, the holder is OME for an LED and the Haynes man shows a pic of it being an LED. I got a pack from Maplins and put one in and it glows, goes out when the engine starts and the batteries are getting about >13v with engine running.
So is it an OME LED or what, and am I OK to put a Maplins LED in?

The warning light is an LED but the printed circuit board has a bypass resistor fitted across the led to act as a bulb load to energise the alternator.

I can only surmise that the led is being able to excite the alternator but as a led will be around 5 or 6mw compared to the 2w that a bulb gives you it is stretching it's capabilities a bit. The only thing that I can think of is that you have a modern self-exciting alternator fitted instead of an original.
I just did a quick check on one wiring diagram (1980 Air cooled) and it is marked as a bulb not led.
It will be interesting to see what others have encountered whilst delving into their pods.

E D I T after above:
Aaahhh - so they are still operating on around 2w for excitation.

Sorry to contradict, but afaik that's not quite how it works, well not on the later WBX'ers anyway (I know little about air-cooled's = may well be correct info for them ). The alternators are self exciting. It is an LED and it has a live feed to it's +ve side (via a dropping resistor to give the ~2V the LED uses). The blue wire that comes from the alternator sends i'ts full output (around 13.8 V) to the other leg of the LED when the motor is running. So, when the engine is on but not running, the LED has a circuit to earth through the alternator and so lights up, but when that blue wire becomes "live" after the engine is started up the voltage on BOTH legs of the LED is then the same, so no current flows and therefore the LED goes out.

The blue wire is also of course used to turn on the split charge relay, as it goes live when the motor is running.

Just had a quick look at an 86 diesel - yes, you are right it has a resistor both sides of a led. (not the full 13+v to the out leg)
So we are both right. That indicator is for a more modern self exciting alternator as I said it may be.
It shows the value of specifying exactly what year and engine when asking a question.

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So, Ian and Lins, back to your problem. Perhaps start at the beginning.

1= Yes the Maplins LED is fine.
2 = What is the voltage on the leisure battery when the engine is running at a fast tick over ?
3 = Do you know where your split charge relay is ?

ghost123uk wrote:

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So, Ian and Lins, back to your problem. Perhaps start at the beginning.

1= Yes the Maplins LED is fine.
2 = What is the voltage on the leisure battery when the engine is running at a fast tick over ?
3 = Do you know where your split charge relay is ?

Thanks to both for the advice.
1=OK
2=c. 13.4v
3=In engine bay

I'm pretty certain everything is OK now. The main problem was a very poor (just a twisted pigtail) joint on the feed wire from the relay up to the Leis Batt that had very badly corroded.

Have a good time in France (taking the bike?)

Glad you got it sorted, though 13.4 is a bit low, you may consider a new brush pack for the alternator at around £13 and 10 minutes to fit. This should give you 13.8 to 14.0 volts and will charge both batteries faster and better.

Ian and Lins wrote:Have a good time in France (taking the bike?)

Aye, off in mid September now, (after the Maplas Steam rally and the fitting of LPG on the 18th of September ) unless we get an Indian summer, in which case we will wait for the rain to re-appear !

Taking the bike = no, but I I wonder what it would be like to do a France trip on a 1959 Matchless 650 with just a small tent, sleeping bag and camping gaz Ummmm

Gotta be pretty cool. I used to do the Bol when it was down near Marseile (sp).
My brother and a few members of the VMCC are regulars at the Coupe Moto Legend near Dijon (June) and I wouldn't mind that as a 'focus' if I can spare the time from work.

You've got me thinking now... Nah, no way Gill would go for it