Battery light?

[Treecutter]

Does anyone know which wire I need to tap into to get a dummy/battery light to work. I’m swapping a big block into the car and ended up not using the factory cluster and I have a red led I was going to use instead of installing a gauge. If I’m thinking right I should be able to run it off of pin 1 and everything work right.

 

[Treecutter]

Anyone??

 

[DieHarder]

Not sure where you found that diagram but it's not the one I have in the manual for the 2005 - 2010 Mustangs. Given the way the circuit works I don't think it's the best solution for what you're after.

Instead of a dummy light I'd suggest a programmable voltage gauge. If you like combo gauges Innovate makes a water temp/voltage unit that displays water temp in the center and uses a string of programmable led's & color (red/yellow/green) to indicate the level of voltage. That way you can set thresholds and alarms (see manual link below):

https://www.innovatemotorsports.com/wp/content/uploads/2022/05/MTX-D-Water-Volt.pdf.

 

[Treecutter]

I found it on a google search. I’d rather not have anymore gauges. I just need to know the light went out so it’s charging. The pinout I found of the cluster looked like the battery light ran through the canbus wire. I was hoping to run a wire to the engine bay from the light and bypass the rest. But it may not work. If I don’t figure anything out I will play with it once I get the car running and see what I can figure out.

 

[VBSTANG06]

If that is the correct plug you could backstick pin 1 w/multimeter set to DC- if there is voltage then ECM is showing dummy light I believe. I think it's worth a shot.

 

[86GT351]

If that is the correct plug you could backstick pin 1 w/multimeter set to DC- if there is voltage then ECM is showing dummy light I believe. I think it's worth a shot.

Logical assumption.

 

[Treecutter]

If that is the correct plug you could backstick pin 1 w/multimeter set to DC- if there is voltage then ECM is showing dummy light I believe. I think it's worth a shot.

I will test it after I get the car put back together. I was just thinking someone may have know which wire it was.

 

[JC SSP]

I don’t think anyone on here will go with an “idiot light” to notify them they have a charging or alternator problem. Stock or aftermarket gauge works best.

 

[DieHarder]

I found it on a google search. I’d rather not have anymore gauges. I just need to know the light went out so it’s charging. The pinout I found of the cluster looked like the battery light ran through the canbus wire. I was hoping to run a wire to the engine bay from the light and bypass the rest. But it may not work. If I don’t figure anything out I will play with it once I get the car running and see what I can figure out.

That was the point. The gauge displays colors on the outside ring. You can set the threshold to say 14v for green. So, as long as it's green you know for certain it's charging at 14v or better and you get a water gauge to boot. Otherwise, simplest workaround would be to use a normally closed relay in series with an idiot light and connected to a 12v source (w/Key On). When the relay activates (alternator is running) it disconnects from the 12v source and stays that way until the key is turned off. However, it won't necessarily tell you how much voltage the alternator is putting out. Hence, the reason to use a programmable gauge to monitor the voltage output.