It is possible to replace the bulbs in these button units. I have done it myself. I have not replaces the lights in my TB yet but I had to do this on my Yukon. You need to very carfully pry out the button from its seat in the steering wheel. If the wiring harness is any thing like the Yukon there is not ANY extra wire and it is a bit of a trick to get unhooked but it is possible. Once the button is out you have to carefully take the switch apart by taking off the back. It is tough but possible so just be paitient. Once inside the switch you will find two bulbs on a surface mount board. This is where one better be comfortable with a soldering station. By carefully heating the base the old bulb will come off. Be careful as you will need to resuse the base. The bulb (Radio Shack #272-1092) is the bulb(s) you will use. Remove the old bulb and also any cover that may be on that bulb. Again my Yukon had a blue filter on the bulb. I was able to get this off and resuse it. After you remount the bulb in the base you need to solder it back in place onto the tow pads. Carefully put the switch back together. You can now put the switch back in. I found that a 90 degree bend in a hook helped "hold" the harness connector so I could snap it back in.
In hide site I should have taken a few pictures. I did this project one afternoon and never though about pictures until I got done. It never occured someone else may want to try this and save the $$ of the switch. I am cheap so 2.00 for lights was better than a new switch. Besides I have a sweet soldering station the wife bought me for fixing a circuit board problem in our washing machine, so I thought I would give this a try thinking what did I have to lose. If I do it again I will take pictures.
Ask me if any thing needs to be cleared up and I will do my best
Hope some of this may help
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