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Charging warning light LED conversion

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Novamonte

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Hi! I have a BT7 Tricarb in pretty much original condition, positive earth, dynamo, original regulator and so on. As the high beam and charging warning lights are very dim and difficult to see I plan to replace them with a blue and a red LED. I have found a silicone LED holder that fits nicely in the holes in the back of the instruments and with two cables that would make it possible to use them even with positive earth (by simply connecting the + cable from the holder to earth). I am however not sure if the charging system will work with an LED instead of a filament lamp or if it depends on current being able to pass through the lamp (which an LED obviously will not allow). Has anybody tried anything similar with success or has enough knowledge of the charging system to confirm whether the conversion would work?
Cheers
 
Not sure about the use of an LED, but if you want to maintain at least the original look of the indicator lamps, then both of them should be red. Blue high beem lamps did not come along until later in the series.
 
There are LEDs available for dash lights; for example:

https://mossmotors.com/led-dash-bulbs

The speedometer and tachometer have colored lenses for bright headlights (blue) and charging (red); at least on my BJ8. I originally replaced all the incandescent bulbs with LED, and they all worked as expected, but came across an admonishment in the Moss Motors catalog that LED bulbs should not be used in the charging circuit. Although I never had an issue using an LED in the charging circuit I bowed to the catalog and other sources--including someone on this forum (Richard M?) who is knowledgeable--and put the incandescent bulb back in (I forget the explanation). While you're at it, consider a safety upgrade for our wimpy running/brake lights:

https://litezupp.com/epages/ac0e8ca...ab-e6c1-4d6b-ab90-9213bdc3f061/Products/L57RP

LED on left:

LEDs.JPG
 
Thank you so much Rob and Bob, very helpful! There are no colored lenses on my BT7 (older style tach and speedo in black and champagne color). There may well have been in the past though. As per Rob's post I will use red lights for both. I had searched the Moss and AH sites for positive earth LED's but had somehow missed these. This is of course a much simpler solution for the instruments. I will also try them for the charging and headlight indicators and buy red + new holders if it works. Thanks also for the link to the running/brake light buld. I had planned to add a LED in the reflectors as per this post: https://www.healey6.com/Technical/Conversion of Reflector to LED.pdf and connect them in parallell with the existing brake/indicator lamp, but a positive earth bulb is of course simpler - I wasn´t aware that these are available. I guess I may have to add resistors to keep the flasher going though, unless I can find an electronic replacement that works with positive earth. Perhaps simply switching the connections will be enough - I will test that.

Again, thanks for your help.
 
someone on this forum helped me with the lense issue. i had one but the other one was gone. take a red folder tab and punch a hole with a drift. then just a dab of glue and stick it in. quick and cheap. looks like the other one i found that was in my speedo.

i converted to alternator but when my alt stopped charging i could see the bulb pretty easily.

IMG_0238.jpg
 
Thanks Drone Dog - excellent idea. I have a set of drift punches, one of which should certainly be the right size, so I will try that.
 
Moss says their exterior LEDs 'require negative ground,' so I assume the flasher is for negative ground cars only. The resistor kit should work with positive ground--resistors don't care which way electrons flow--and the LiteZupp people supply positive ground exterior LEDs (they're Triumph enthusiasts).
 
would you still need an electronic flasher if you leave your front bulbs alone? they should trigger the normal flasher shouldn't they?
 
Can't say for sure--I've only put LEDs in my BJ8's running/brake sockets; flashers are a separate circuit--but I'd assume you'd need either the electronic flasher or the resistors as each side's front and rear turn signals are on the same circuit. You could call the Moss people and ask.
 
I don't think they will draw enough current. One bulb recently failed and the result was faster blinking and that the indicator lamp didn't work, so I assume that the result would be the same with an LED. The resistors are easy to install though.
 
When i put LEDs in my BT7's brake / turn signals, one side worked fine without a resistor, the other didn't. Easy to install at the flasher relay on the inner fender.
 
Most of The little colored lenses that were glued into the indicator bezels have by now fallen out due to the failure of the original glue. If your lucky, you'll find them loose inside the instrument when you open them. I very seldom see both of them installed in even well restored cars, especially the early 3000 cars.
 
I'm not sure the charge indicator light will work using a LED.

IIRC, the light goes out when the generator output voltage and battery voltage are closely balanced. When the generator isn't charging, the lamp is lighted by battery voltage, but when the generator is charging the generator voltage is slightly higher in the opposite direction, but not enough to light the lamp. Thus, the lamp could see voltage in either direction. That's ok with incandescent bulbs, but LEDs are polarity sensitive.
 
John Turney said:
I'm not sure the charge indicator light will work using a LED.

IIRC, the light goes out when the generator output voltage and battery voltage are closely balanced. When the generator isn't charging, the lamp is lighted by battery voltage, but when the generator is charging the generator voltage is slightly higher in the opposite direction, but not enough to light the lamp. Thus, the lamp could see voltage in either direction. That's ok with incandescent bulbs, but LEDs are polarity sensitive.
Click to expand...

Best explanation I've heard yet. The LED in my BJ8's charging circuit seemed to work the same as a bulb with one exception: the LED was either full on, or off; the incandescent bulb would fade away as engine speed increased. Although it appeared to work the same, the LED probably didn't extinguish until a bit higher RPM/charging voltage.
 
Thanks all for very useful advice. This forum is a fantastic source of wisdom for a rookie AH owner.
I thought there was an issue with using a LED for that purpose, but now I also understand why.
 
I changed all the dash bulbs in my TR6 to LED’s. Now I can actually see my gauges. The only one that did not work was the ignition lamp. I ended up putting the incandescent bulb back in for that lamp.
 
Novamonte, I don't know much about LEDs but I do know how the ignition warning light works. The ignition warning light has two hot wires on it. There is a white wire that is connected to the ignition switch's on position, this gives voltage from the harness (it would be battery voltage when the generator/alternator is not running). The other wire is either yellow or brown/yellow depending on the year of the car. This is the wire that you see at the generator terminal. When the generator is not charging this wire is effectively going to ground through generator. Hence with the ignition switch turned on but the engine not running the white wire is getting voltage from the ignition switch, supplying it to the bulb holder and the other side of the bulb is grounded thru the generator and the bulb will light. When the engine is started then the generator starts to charge the brown/yellow wire is no longer grounded and it has the charging voltage applied to it. Now in this state the bulb has the same voltage on both sides of it and the bulb will not glow. With the same voltage on both sides, there is no difference in potential and no current can flow. In some cases where the voltage regulator is adjusted to high you can see the light start to glow. This is because the generator is putting out too much voltage and is much higher than the system voltage which is much nearer the battery voltage and the bulb sees a difference in potential and can glow.
 
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