Thread: Aftermarket gauge light issues

I've got 3 VDO gauges in my car. All have LEDs in them and all get both the ground and power from two wires bridged across all three units (see the red power wire in the image below). One of the gauges has already burned out one LED. Now in the same gauge the second bulb is on the way out, in the span of 6 months. The other two gauges light up fine, in fact the second bulb that is going out was one that had worked for a year in one of the other two gauges. I have used the same bulbs for quite some time in my dash cluster with no issues, so I don't believe they are cheap/bad bulbs. In that one gauge, the bulb will start flickering, sometimes fast, sometimes slow. After a few weeks like that, it will just go out.

I figure the gauge light connector must be bad since I know it isn't the bulbs and it isn't either the power source or the ground as the other two are working great. Am I on the right track?

Most will say to solder the wires to get a better connection, but I'd have done it the same way if I was you.

I've seen LEDs flicker even with a good connection. This typically means the LEDs are drawing more current than they can handle and are on the way out. Do you know what size resistors are being used for the LEDs?

But if it was a resistor issue, wouldn't all three be flickering, not just one?

Well there isn't anything wrong with the resistor, its size is just allowing too much current to the LEDs, which causes them to fail quicker. The weakest LED will fail before the others, and start flickering first.

If you care enough, I can figure out if this is really the problem if you can get me a basic wiring schematic and the resistor(s) color code...

The three lights are wired in sequence from a wire that is tapped into the wire that provides the power for the light around the cig lighter in the car. I cannot recall which bulb of the three is the first to receive the power before sending it off to the next one, but it is entirely possible that the one flickering is getting the power first. As I said, it is directly wired to a tap in that cig lighter ring for power so the lights turn on with my dash lights. I don't know what the resistor color code is for it or where to find it other than to say that if it exists, it is somewhere in the OEM harness in line with the wire I tapped.

Is this what I would need?

Load Resistor Kits

The resistors for your LED gauge lights are probably within each gauge. You could add an additional resistor outside the gauge to supplement what is already within it, but since you don't know what size resistor is used in the gauge, it's hard to tell what size to add.

Adding a resistor outside the gauges wouldn't fix the LEDs that already went out, it'd just keep the rest of them from going out. At a guess, I'd go for the 25 ohm resistor, but that one is a lot larger than what you need for an LED.

You'd have to replace the LEDs to fix the ones that broke, AND add resistors to keep them from going out again.

The math is pretty simple, but I use this LED resistor calculator all the time. Again, you still don't know what resistor is already being used within the gauge, so this doesn't help you much

If you really want to fix it, you'd have to take the gauges apart and see how the LEDs in them are configured.

Or are you using something like this?

Very similar to that. This is the bulb/socket I used in my gauge cluster but I used the same bulb in the VDO gauge that is flickering:




I figured the bulb that burned out/flickered is toast and I can replace it. I don't think there's much to take apart in the socket for the VDO gauge, it seems like a simple socket with the wires attached. I don't think there's anything else in there. I presume that if I got a resistor, it would fit on the power wire before the power got to all three gauges. So: Power source ==> resistor ==> Gauge 1 ==> Gauge 2==> Gauge 3. The gauges came with a standard wedge bulb, I put in the LEDs myself. Here's the socket it comes with, which according to that page a flickering bulb is a symptom of a bad socket:

VDO Gauges 600840 - VDO Replacement Light Bulb Sockets - Overview - SummitRacing.com