[wirenut699]

I searched the forum and did not find any other complaints like yours. Seems odd. I've never had this problem. My factory lamps in my 96 blazer lasted 9 years.

When your brother replaces the lamps each time, does the new one work immediately? with no effort or jiggling?

Did he, or can he check with an OHM meter if the actual filament on the old lamps are actually open circuited? (broken filament)

Check the socket for signs of heating and / or corrosion. It does not take much corrosion to stop 12 volts. Corrosion can give the impression that a filament is gone. The act of pulling out the old lamp and inserting the new lamp can sometimes scrape away enough corrosion to get the lamps working again, temporarily.

You say it's been happening since he got it - as in - for 6 years?

No insult intended, but make sure your brother is using the correct lamp. Different lamps even though they may be auto type can be rated 12volt or 14 volt and have different hour ratings. 12 volt lamps burn out much faster than 14 volt lamps.

If he has been changing them constantly for 6 years, he may have lost track of the correct lamp.