Thanks! the aftermarket LED is blue and it's noticeably bigger than the stock red led. can i still measure the voltage of a blinking led? i would like to measure the voltage of the aftermarket led as well.
also, i wanted to connect the aftermarket led wires to the stock wires of the C24 connector (orange) at the back of the center panel switch assy. but it seems that may not be possible unless the aftermarket blue LED is currently seeing 12v which may not be the case since it's attached to the pcb of the aftermarket alarm
I'm not sure I'm fully understanding you. Is the aftermarket LED dangling on wires by itself waiting to be installed somewhere, or is it soldered to the PCB of the aftermarket unit?
Do you want to replace the stock Red LED with the Blue, or just power the stock Red from the aftermarket unit?
If you simply want to power the Red from the aftermarket unit, depending on how it's set up, you have 2 options. If the Blue is on its own wire, you're going to need to trace the wires from the PCB on the stock unit to see which ones power the stock LED. Then, cut them from stock power (tape up the stock wires on the main harness; that's live voltage) and splice the wires from the stock plug into the wire for the blue LED (cut the Blue out of the equation).
If the Blue is on the aftermarket PCB, you'll need to solder a length of wire to the aftermarket PCB, and then splice into the stock plug.
If you remove the blue, you'll need an inline resistor. Blue typically takes about 3.4v versus 2.0v for Red, so you'll want to lower it to a Red safe voltage range. An online LED Resister calculator says that you'll need a 47ohms, 1/8w resistor for that. Just solder it inline either immediately before or after the LED, it doesn't matter. It doesn't matter the direction it faces, either.
If you leave the blue, it will work, but they will both be pretty dim, as neither LED will get their full voltage.
I won't bet my life on it, but I can guarandamntee you that neither LED is receiving 12v, so don't worry about that.
From my limited experience, physical size doesn't *necessarily* mean a change in voltage. Even those smaller SMD LEDs seem to follow the same basic voltage patterns. It's just the housing that refracts/magnifies the light that changes. Of course, I can't promise anything, but that's what I've typically found. Case in point, the green LEDs for the Auto-Windows are actually SMDs. I removed those and soldered in some white 3mm LEDs and they work great. White LEDs can take a higher voltage than green, so I wan't TOO worried about blowing anything.
You should be able to measure the flashing LED the same. The flash isn't in the LED, but somewhere in the circuit before it. It's just a break/reconnection of the voltage. So when you measure, you'll just get a break/reconnection also.
You can measure from the PCB itself if you're careful. Make sure all connections are plugged in, and hold the MM prongs to the metal 'tape' on back of the PCB near your LED. That's what carries the current to/from the LED.
