I recently acquired a 1992 Volvo 740T that had every courtesy dash light burnt out. A quick trip to the Volvo dealer revealed that each bulb/socket assembly would be around $15 each! I was facing the likelihood of dropping $60 and another $12 for 3 wedge base bulbs for the other courtesy lights.
Here is how I replaced every burnt out bulb for less than $6, not including shipping.
Step 1: The Offending Assembly
This bulb assembly would cost me about $15 dollars at the dealership, the second required wedge base bulbs, about $4 each.
Step 2: Replacement Bulbs
After removing the burnt bulbs, I carefully measured them and found replacements at 1000bulbs.com, each package has 10 bulbs. That leaves me plenty for another project later on. You can see in the second picture how they match up.
The wedge base bulbs are easy; grasp firmly, pull. Replacement is the opposite.
The one piece assembly required a little more work.
Step 3: A Little Doctoring
Using my trusty Dremel and the thinnest fiber cutting wheel I could find, I made a cut up the side of the assembly, exposing the bulb lead. I had to cut just up to the base of the socket to make it easier to thread the new bulb leads.
Once the bulb leads had been threaded through, all I had to do was solder them down and snip away the remaining lead.
Since the bulb plugs into a wire harness, there is no need to shield the exposed wire.
Step 4: Finished
I pulled the harness from behind the dashboard to test the lamp assembly. It works fine and responds to the dimmer as well.
NOTE: After I reassembled everything I discovered one bulb wasn't working! It turns out, a soldered lead had failed, so I re-soldered it and it worked perfectly (point is, avoid cold solder connections).