Alternator Issues After Replacing Dials

[Guest ScottG]

I previously had the standard sierra dials installed in my 2B, I have since removed these and installed an ACEWELL digi dash,. This setup doesnt have an option for a alternator warning light.

 

So I purchased a SAVAGE warning light which I planned to use as this function.

 

However I cannot get it to work-

 

Can someone please confirm that I need a light in the system to start the charging of the alternator - searching would suggest this is the case. At the moment the alternator is not charging the battery- the volgate is 11.9v with the engine running.

 

I then go ignition live to one side of the light and the blue wire from the standard dials to the other side?

 

The SAVAGE switch is a LED so will I require a resistor between the two connections also? If so what size?

 

Thanks in advance!

[Dave R]

not sure that you will get it to work with an led, really needs a bulb to provide the initial current to excite the alternator

[Guest ScottG]

Blast, the Savage light was going to complete the set. Surely a resistor accross the two pins acts in the same way a filament bulb does?

[Dave R]

you may make the alternator excite, but you wont get correct indication from the led, as it needs to allow current to flow both ways...

 

and an led only works the one

[Guest ScottG]

So I need to put a standard 12v 1.2w bulb in to get both the correct indication and excitation?

 

Could I put a bulb in Parrel behind the dash somewhere to excite the alternator accordingly? Then take a 12v feed from that and a GND to the Savage warning light on the dash?

 

Failing that I guess something like this is what I need? http://www.cbsonline.co.uk/product/Battery|Ignition_Warning_Light_Large_Aluminium_Bezel_WLLBATT

Edited December 30, 2011 by ScottG

[Longboarder]

A recurring theme. Alternator with LED warning light. Depends on the alternator wiring. Most denso like an ignition live excitor and a bulb, ie two separate wires to the alternator. Lucas just the bulb which also carries the excitor current. I have just checked a spare standard warning lamp at 25 ohms so a 25 ohm resistor should be worth a go.

 

Nigel

[Guest russell555]

ok...daft question alert..

 

when i removed my sierra dash and put in an etb digidash,the first thing i noticed was that i had to rev to above 3000 rpm to excite the alternator to start charging....

just a thought?

[Guest ScottG]

Its a Bosch alternator.

 

I will raid the cuboard at work next week and see what resistors I can come up with.

[Longboarder]

I'm no good with electronics but it does seem that dash warning bulbs are pretty small wattage so can only provide zero point something of an amp as the excitatory current. The alternator just needs to get started on this and then the regulator hives off as much excitatory charge as it needs to maintain voltage. So any resistor from 10 to 50 would probably do. Might you need to put in a diode somewhere or some other sort of electronic trickery. Hang on a sec. A LED is a diode. Told you I knew close to sweet FA about electronic stuff.

 

Nigel

[Guest ScottG]

Sucess.

 

Took the bulb out of the old instrument cluster and put it in parallel with the SAVAGE light and the light now operates as expceted (albeit it after a blip of the throttle)

 

The resistance of the bulb was only 15-20ohms so I would go with your 10-50 as above.

 

Fantastic help again all. Many thanks.

[Jez Morton]

I do know a little bit about electrickery, on the Sierra the charge bulb is usually 1.2 watt which should equate to a resistor of around 120 ohms with a power rating of 1.2 watts min i think you can get 1.5watt. If you wire this in parallel with the LED this will work fine I don't think any extra diodes are required.

 

Jez

 

Just to add when I worked out the resistor rating I based it on the power rating of the bulb, measuring the resistance of a bulb is not the way to go as when energised the filament heats up to around 2000 degrees and with heat resistance increases. Think about it a 10 ohm resistor will allow a current of 1.2 amps to flow as opposed to the 0.1 amp a 1.2 watt bulb will pass. Also a 10 ohm res would need to be 12 watts, compare a 12W and 1.5W resistor. Most standard resistors you get from Maplins etc would be 0.25watt.

[Guest QuadraDave]

Found this diagram on on a website hope it helps Dave D

Edited December 30, 2011 by QuadraDave

[Longboarder]

Stone the crows, there is a second diode. I must be a natural at this. Sort of intuitive thing I guess amongst us geniussesses .

 

Nigel

[fry61]

To-day diodes,tomorrow thyristors;questions will be asked!!

[Guest peter2b2002]

I allways thought it was 12v through a bulb to the alternator exite it which made the bulb glow the when the alternator was running and charging it put 12v back through the bulb via a diode thereby turning the bulb off,

peter2b