Alternator Led Warning Light

[Guest mcramsay]

Righty oh, apologies if that came across as argumentative, I genuinely wanted to know the reason! Sadly I can't find a lamp that will match the other LEDs I'm using.

[Longboarder]

I read it simply as a question, not argumentative at all. And thought I will supply an answer.

Just shows how complicated conversation is without tone of voice, hand gestures, posture, facial expression can be.

 

Nigel

[Guest mcramsay]

Ok I I bought a warning lamp, and the resistors I mentioned earlier, I want to use the led on the dash as it matches the other instruments. So should I wire the warning lamp I bought in parallel with the led and hide it under the dash or use the resistor? I want to use the option least likely of blowing the led or causing a fire!!!

[Guest chris brown]

IMO I'd use the resister as it will be more reliable than the hidden bulb

[Guest mcramsay]

Well tried with the resistor and it blew the led when I started the car. I managed to drill out the led from the holder and file up a red warning lamp holder so it fitted in the existing led housing. So now it all looks the same but the warning led is now a lamp with a red glow hidden behind the decal . Run out of time tonight but I will give it a go tomorrow!

[Guest mcramsay]

Still having issues, with the bulb connected it lights up but the alternator does not start to charge and the light stays on. I put a connection straight from the lamp down to the alt to bypass the car wiring. But still the same result. The bulb has a resistance of 30 ohms.

 

If I take the light out of the equation and put a switched 12v into the alt rather than going through a lamp it all works fine, the alternator charges fine. I'm wondering if the bulb is not letting enough current flow to the alternator? Should be giving the alt 0.4A currently

[sj-bradley]

How did you measure the resistance of the lamp?

 

Sounds like you did this when cold. This will lead to a false reading as it will be much lower than when the lamp is working and lit.

 

That would make it a 5 Watt lamp which is too much for an indicator on the dash board and would be as big as a sidelight. What is the wattage rating or can you measure the current through the lamp when attached to the battery?

 

For 1 1.5 Watt lamp on 13.8 volts (typical battery) You would expect approx 108 mAmps (milli amps) or 0.1 amps.

 

Hope this helps

Simon.

[Guest mcramsay]

That makes much more sense, thanks Simon. I got to the bottom of it in the end, the lamp is not giving enough to get the alt to charge. Well it does work I have to rev the engine slightly to get it charging. I will look for another bulb at a later date.

[fry61]

Sounds like normal -- alternator will not give output on idle -- 8/900 rpm -- just try winding the throttle stop screw up a little & the alternator will probably kick in around 1000/1100.

 

Don't forget to re-set idle though.