ABS and Battery Cluster Lights Always On?

[Basilius]

I recently replaced all the bulbs in my vehicle (headlights, tail lights, dash, cluster, etc) with led bulbs, and now the ABS and Battery dash cluster lights are always on when the engine is running. I haven't had any battery problems, there are no blown fuses anywhere, and I only have rear wheel ABS brakes. Is this something to be concerned about, or is it because of the led swap?

 

[Uncle Gump]

It has something to do with the led swap...

 

[Dirtman]

I believe the ABS needs to see voltage from the brake lights. I'm not 100% sure. With LEDs the voltage drop from the lights may be to minimal for the computer to see the difference. Load resistors MAY fix the issue but I'm just guessing here.

I don't know why the LEDs would effect the battery light though. I would simply test the battery and alternator, may just be coincidence that the batt or alternator is simply bad.

 

[Curious Hound]

Yeah. At least the battery light is dependent on resistance also because of the way that circuit compares voltages.

@RonD has a writeup on that somewhere in bunches of threads.

 

[RonD]

The Battery Light and ABS Light in the cluster are like most of the other warning lights, they each get 12volts with Key ON, and are then Grounded by their respective devices/units which causes them to light up

The Battery Light circuit does have a resistor by-pass in case bulb should burn out, so alternator doesn't quit working
But shouldn't matter if bulb is LED or incandescent.
Simple test would be to test battery voltage engine off, 12.3v to 12.8volt is expected
Then start engine and re-test battery voltage, 14.3v to 14.8volt is expected<<<if still 12volt then alternator is OFF, not working

ABS bulb doesn't have a by-pass its just gets 12v key on and ABS module grounds it to light it up

Both of these bulbs ground wires are on the 10 pin connector on the cluster, may be they got shorted to ground when plugging back in cluster

If alternator is not working then unplug the 3 wire connector on alternator, test light green wire, it should have 12v with key on/engine off
If not then LED is blocking voltage so you would have to change it back to incandescent bulb
LED stands for "light emitting DIODE" and a diode only allows electricity to flow ONE-WAY, which can be a problem in a circuit like that

 

[Basilius]

The battery is about 14.4v with the engine running and about 12v with the engine off, so I think that the alternator is okay. I don’t understand about the led bulb blocking voltage. Is this a problem that needs to be fixed? I might try swapping different led bulbs or just reseating them and see if that helps.

 

[Curious Hound]

I don’t understand about the led bulb blocking voltage.

LED'S are not really "bulbs" like traditional incandescent lights. They are semiconductors. They only conduct electricity under certain conditions. In the case of an LED, they only allow current to flow in one direction. Similar to a check valve in a piping system. You may just have those installed backwards so they are not conducting. In other words, blocking current flow, which is what Ron was referring to. In the case of the battery light, when the engine is running, the alternator voltage is greater than battery voltage. If the voltage difference is high enough, currentvwill flow back from the alternator to the battery and could make the backwards LED emit light.

 

[Basilius]

The LED bulbs were the problem. I tried a bunch of different leds (including non-polarity) with the same results. I replaced them with halogen bulbs and it fixed the problem.