Author Topic: 1100 Sport Indicator Wierdness  (Read 663 times)

Online Old Jock

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1100 Sport Indicator Wierdness
« on: April 18, 2019, 06:42:19 AM »
More out of academic interest than anything else really

So I've removed the standard instrument cluster and installed SpeedHut Gauges. The Speedo has 3 lights embedded in it. So I thought I'll use one for neutral one for high beam and one for the indicators

The standard cluster only uses one bulb as a warning light, this is goanna be easy, I just wire the led I want in the gauge to light to the single one that was used in the standard panel for the indicators and I'm done.

Not quite

Just turnned on the indicators and now I have all of them flashing no matter if I choose left or right.

Looking at Carl's diagram it appears (to me anyway) that both indicators have a parallel feed to the bulb, no diodes WTF. I would have expected the bulb to allow the voltage to backfeed to the opposite indicator circuit.

Thinking about it it's probably because the indicator warning bulb is relatively low resistance compared to the LED.

When the bulb is used the resitstance is low, relatively speaking, so not much current will backfeed.

However introduce a high resistance LED and more current will take the line of least resistance (literally) and backfeed to the opposite circuit

I just posted because this could happen if somebody decided to install LED warning lights in place of the standard bulbs.

I can check this easily by breaking the warning light connection, if the indicators return to normal then I'll need to install Diodes into the 2 separate lines

Johnn 

Offline RinkRat II

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Re: 1100 Sport Indicator Wierdness
« Reply #1 on: April 18, 2019, 08:08:45 AM »

       They do make flashers that are LED compatable, don't know if it will help in your case but it may save a headache or two.

           Paul B :boozing:
A Miller in the hand is worth two in the fridge.

Online Old Jock

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Re: 1100 Sport Indicator Wierdness
« Reply #2 on: April 18, 2019, 08:58:35 AM »
Hi RinkRat

That's not the problem with this fault. but the thought is appreciated & I posted simply as a warning or for anybody searching on this type of problem

When you only have one warning light on the dash for both indicator circuits, obvioulsy a wire has to be run from each of these 2 circuits to the bulb. The problem is that the current coming from the circuit you want to light the warnning bulb can then feed into the other circuit and then all the indicators come on not just the side you have selected. Electricity will always take the path of least resistance until it finds ground (or chassis in this case)

Two ways around this are the warning bulb resistance is low relative to the  main circuit's resistance so that (nearly all) the current flows through warning bulb and none back feeds into the unwanted circuit OR diodes are installed into each circuit to prevent the current backflowing where you don't want it to go. A Diode acts like a check valve, so the currennt can only flow in one direction.

It just surprised me that the bulb resistance is low enough in the case of the stock set up to prevent the other circuit recieving enough current/voltage to light it. It's just another example of Electrical Luigi's circuit design wierdness schemes.   

Offline Murray

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Re: 1100 Sport Indicator Wierdness
« Reply #3 on: April 18, 2019, 09:08:30 AM »
If you put a diode either side of the LED with the cathode towards the LED it should block the current from the other side. Obviously make sure its 12volt rated. A LED flasher won't help in this situation if my understanding of the circuit is correct.

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Re: 1100 Sport Indicator Wierdness
« Reply #3 on: April 18, 2019, 09:08:30 AM »

Offline wirespokes

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Re: 1100 Sport Indicator Wierdness
« Reply #4 on: April 18, 2019, 09:25:35 AM »
Did disconnecting the flasher LED stop the rest of them flashing?

So far, it all looks like hypothesis to me.

From what I know, LEDs are much much lower resistance than incandescent bulbs. To get them to work as turn signals with a regular flasher requires the addition of resistors.

Online Old Jock

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Re: 1100 Sport Indicator Wierdness
« Reply #5 on: April 18, 2019, 10:14:34 AM »
No its not hypothesis Wirespokes

LEDs have a high resitance, unless I've totally lost the plot

The higher the resistance the less current flows V=IR (aka Ohm's Law) also the higher the Wattage of any device the lower the resistance, otherwise current will not flow to support the Wattage
 
When installing resistors to keep current flow the same when LED indicators are fiitted the resistors are placed in parallel not series. The voltage then remains the same and some of the current flows through the resistor to compensate for the lack of current the LED requires (a horrid way of doing it anway)

Disconnecting the flasher simply stops the indicators working at all as the flasher provides the power to the switch, the switch selects the circuit, but with a common warning light there is point after the switch where the circuits are joined and some method or device is required to stop the current flowing into the circuit that you do not want current flowing through

I just tested the circuits with Diodes and as Murray indicated no crossover between the Left and Right circuits, problem solved

John

Offline wirespokes

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Re: 1100 Sport Indicator Wierdness
« Reply #6 on: April 19, 2019, 12:05:59 AM »
Ah, yes, you're right! I'd forgotten the resistor is placed in parallel with the LED, not in series. Thanks for that.  :bow:

Sounds like you do have it all figured out!

 

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