Here are the tools and steps required to perform the interior light switch mod.
If you are not technically inclined please purchase the fabricated bypass circuit from http://www.rv-partsplus.com/home/accessories/ per 87silver ref: Dome Override thread https://www.chevyhhr.net/forums/problems-service-repairs-42/dome-override-26350/

Decided to use the fuse panel / bcm cover as opposed to locating it elsewhere, moved the fuse information about 1" to accommodate the new switch. Your choice of location within the limits of the length of the new circuit.

Tools
25 watt Soldering Iron
Wire Cutters
3/8" drill (battery powered preferred)
3/4" hole cutter bit or Forstner bit
1/8" drill bit (to center drill 3/4" hole)
Dremel power tool (diamond cutter and mini drum sander)
Exacto cutter or sharp knife
Crimping tool

Parts and supplies
Solder
18 gauge wire (Walmart auto dept)
Fuse holder (Radio Shack # 270-0015)
10 amp Switch (Radio Shack # 275-0693)
10 amp ATM mini fuse (use Dremel to remove top)
1/4" flex or spiral loom
Electrical Tape
2 small insulated push on slide connectors (to fit switch connections)
Heat shrink tubing

Directions:
Assembly -
1. Fill void in modified fuse with epoxy (assure that the fuse link in the center is removed)
2. Cut fuse holder wire so that 1/2" of wire is left on it and strip 1/8" of insulator off on both sides
3. Solder a 3 inch 18 gauge wire to one side of exposed fuse connection
4. Solder the other end of the above wire to one side of the fuse holder
5. Use heat shrink in both soldered ends of the wire above
6. Solder a 8" piece of 18 gauge wire to the opposite side of the fuse holder
7. Crimp the other end of the 8" wire to a slide connector with end stripped about 3/8"
8. Cut a 15" piece of 18 gauge wire
9, Solder one end to the other fuse terminal (see images) strip end about 1/8"
10. Shorten the 15" wire so that it is the same length as the total length of fused side
11. Use heat shrink at fuse connection of the 15" wire
12. Solder other end of this wire to another slip connector
13. Circuit is complete

Installing -
a. Remove fuse info on rear of cover - relocate info label 1" to left from original position
b. Drill 1/8" pilot in fuse cover panel where shown in image or in your desired location
c. Drill 3/4" hole using pilot hole as a guide with a 3/4' circle cutter or Forstner bit
d. Enlarge this hole about 1/32" in diameter using a small Dremel drum sand or similar tool or file
e. Mount switch in cover panel
f. Push slide connectors onto switch
g. Remove the 10 amp fuse from position # 27 and insert the modified fuse end of the circuit into fuse position #27
h. Position or push excess circuit loom/wire into open area between the bcm connectors
i. Re-install fuse cover

Images:

 

I guess I'm missing something..........what does this do?

 

Mike - It will allow the interior lights to be turned off for those that do not wish them to be on with the doors open for an interval of 20 minutes. For example; If you are working on the vehicle, cleaning it, or any other reason one may have the doors or liftgate open for an extended interval. etc... The bcm timer that dims the interior lights is set for 20 minutes as opposed to other GM vehicles that are set for 5 minutes.

Please excuse no explanation.

Visit the thread Deflace posted https://www.chevyhhr.net/forums/showthread.php?t=26350

 

to me that looks very similar to the 6 dollar aftermarket switch set for foglights sold at pepboys if you add a fuse tap to it

 

Very thorough write up.

 

Thanks, will check this out at my local Pep Boys and see if it will work for those interested.

 

I might just have to do this.

 

Guess one could modify this auxiliary harness kit, its cost is about three dollars less than the parts listed, it uses a glass buss type fuse as opposed to a mini ATM.

 

Why change the appearance, spend the money, and risk making a mistake when all you would need to do is remove the fuse from the panel?

 

I know this an old topic and I just remembered to come back to. Basically, because I hate the fact that my Blue Lightning did not come with a dome override switch (which was a dumb idea on GM's part especially since this is a vehicle made for tailgating and having the hatch open) so I wanted to check on some options other than pulling the panel and removing the fuse each time. I don't blame the dealerships or my salesman as they have been very accommodating all the time. When I was looking for my next vehicle, I even pulled up the 2008 manual and read it that way I knew what I was getting. The 2009 manual said the same thing and although GM did not offer it with the 2009's, it was still in the manual. This is a grudge against GM and Chevrolet for making this dumb decision based upon a so called survey that supposedly said that customers did not want the dome override switch which I find hard to believe. It probably was more like a cost cutting move the same as the radios since mine does not have the function to control the chimes.

I had the idea of just installing a 2008 HHR Light with the dome override switch and every service manager that I talked to from about five dealerships said that would be possible if the body control model of the vehicle was recalibrated to accept the light. The wiring for both the 2008 and 2009 are the same. However, I was told by a rep from GM that the 2009's did not have the calibration feature which I find that hard to believe. If anybody can let me know more about this, cool. In any case, we'll see what happens.

Thanks

Blue