Alternator LED

[danielbrookes]

Hi, hope this is an easy one.  At the moment if I run the car I get 13v at the battery and the LED battery light is dimly lit.

If I flip the wires on the reverse of the LED the light does not come on but I get 14v at the battery.

Do I need to put a resister in between LED and alternator?  If so how many ohms?  It’s the Denso alternator from Kitspares.

Wiring loom is my own and everything else works without issue.

thanks,

Dan

 

[knights_templar]

If its the small alternator that GBS use on the Zetec, a resistor should not be neccesary.

How have you wired the LED?

should be 

+ ignition live to + of LED,  - of LED to alternator.

[danielbrookes]

4 minutes ago, knights_templar said:

If its the small alternator that GBS use on the Zetec, a resistor should not be neccesary.

How have you wired the LED?

should be 

+ ignition live to + of LED,  - of LED to alternator.

Thanks, I had read that elsewhere as well. I will need to check and confirm for sure after my Sunday morning dog walk; but from memory I have wired it as above. 

[fry61]

I believe LED's are not suitable ---- the "Ignition lamp"  in the olden days was there to give a small feed to the alternator to excite the beastie into producing current; once current (& voltage ) were being made the lamp went out due to equal voltage on both sides of the lamp.

LED's just don't have a low enough resistance to supply the alternator with a start current.

With Florin I have an LED on the dash but have a tungsten filament lamp ( hidden under the dash ) connected in parallel to provide the start current.

[danielbrookes]

Just checked and it is wired as above. My diagnosis is wrong though.

When car is running the battery led is dimly lit.  I get 14.3v at battery, 14.3v on positive side of LED and 11.3v at negative side which comes from the alternator.

Its a type one and is wired as per 

Any ideas what I should investigate?

[fry61]

Just try changing the LED for a tungsten filament lamp -- only needs to be around 5 watts --- it should go out when the engine is running on tick-over or just above (1,000 rpm )

Also check you have a good earth to the alternator body ( use a test lamp or a meter )

Edited March 3, 2019 by fry61
Additional information

[danielbrookes]

Earths good, tried with a bulb and voila - works a treat, bulb goes out and alternator charges.

Is there any way to get it working with the LED? The reason I ask is I have quite a nice little light cluster.  To get the existing LED out will be an absolute faff about.

[danielbrookes]

Bit the bullet and removed my light cluster, I shouldn’t be so lazy! Off to get a bulb that fits and hopefully that will be all fixed

[fry61]

If you haven't already gone to spend your pennies ------------------ it just needs a filament lamp connected in parallel with your "nice little light cluster".  Then hide this extra lamp under the dash. ( could be on passenger side foot-well to give a little illumination for your other half's entrance/exit.

[danielbrookes]

All sorted thanks guys.  New bulb was £1:50 from Halfords, probably not the cheapest but convenient for me.

Car now runs, alternator charging and battery light goes out