Those of you that have installed the HHR rearview mirrors (with autodimming, OnStar, compass AND maplights), you may be disappointed with the dim and yellow light from the map/cabin light LEDs. If you are a reasonable hand with a soldering iron, this is to show how to replace the original LEDs with much brighter and whiter LEDs. Note, the LEDs are surface mount, and not the easiest things to solder, so if you are worried about that, stop reading now!
First, you have to get yourself some replacement LEDs! The ones that come in the mirror are 3.5mm square, surface mount LEDs, running at probably 2700K color temp (or maybe even lower). I didn't want the ultra blue-white LEDs, so I chose to go with 4000K, which is white color, but still with a slight warm cast. I used Phillips/Luxeon 3535L LEDs, they are very bright and available in color temps from 2700K all the way to 6500K. You may wish to use something in the 5000 or 5700K range, but that's up to you. I bought them from Digi-key - cost was just $0.46 each LED (I got 3 in case I needed a spare) plus about $3 USPS post shipping. So with a total under $5, it won't break the bank! This link should take you to the filtered shortlist at Digi-key, for the LEDs from 4000-6500K - click on the part number in the column toward the left, to order your choice: Digi-key LEDs page
OK, after a few days, your LEDs should come in, so time to take your mirror apart. The mirror bezel is simply clipped to the plastic body by 12 clips around the edge. Use a plastic pry tool (like for an iPhone) or maybe a small screwdriver wrapped in tape, to push in at the seam angled toward the body. Start at the bottom right and go all the way round, releasing each clip in turn. The green arrows on this photo show where the clips are:
Once the front and back are apart, undo the 3-wire pigtail connector from the main board and set the mirror, bezel and main board out of the way. Next, undo the two T8 torx screws, marked "1" below. With the LED board loose, you'll need to unclip the plastic lenses from the bottom. Wiggle the board and reflector out of the way backward as much as possible and press hard against the clip marked "2". Takes some effort (DON'T break it!) but once it's free the lens will pop out from below. Repeat for "3".
Once the lenses are out, you'll be able to wiggle the LED circuit board out from the mirror body - the rubber buttons will
bend. Unclip the reflector assembly from the board so you can get at the LEDs. I took the rubber buttons off too, but you probably don't really need to. This is the board with all the 'bits' removed. The cathode/negative sides of the LEDs, are towards the middle of the board (see the thicker lines on the silkscreen):
Now the MOST difficult part - removing the old LEDs. I found the best way was to use two
soldering irons to melt the solder - one in each hand and on each side of the LED (in green circles below), then 'tweezer' the LED off the board between the irons. Your method may vary. The board itself is pretty tough, there's a lot of copper to act as heat sinks for the LEDs, and if you damage the LEDs themselves, it doesn't matter since you're replacing them anyway!
This is what it looks like with the left LED removed:
Now you can solder the new LEDs on. The Luxeon LEDs have one corner indented on the cathode side, so those corner indents should be oriented toward the middle of the board. I cut a thin strip of masking tape to keep the LED in place while I soldered each side. Just touch your iron to the exposed pad area on the board to melt the solder and the LED should settle in.
This photo shows the LEDs lit, after replacing just the right hand one. You can see the LED is MUCH brighter and whiter than the original. To test the board at each stage (recommended) just poke a piece of thin single-core wire into the loose end of the pigtail connector and connect them to a 12V power supply - actually a 9V battery should work too. Red wire is +12V and black wire is ground. Short the white wire (middle pin) to ground to turn both LEDs on, or leave the white wire unconnected and use the buttons to turn each LED on individually.
Then, as they say, "assembly is the reverse of dis-assembly"!
That's all folks. (Cross-posted on all three fora, 'cos not all read every forum.)