Interior Lights Only Work When Key is Turned - 68 DeVille

[Highwayman68]

It always feels good to find the solution to an issue.

However...
I am now concerned about why the wire fried instead of the fusable link. I would suggest having your mechanic replace the fusable link just to prevent what can be an even bigger issue in the future.

[TJ Hopland]

I think he said the link was still in place and appeared to be in good condition. 

Its not unusual to see those style connectors having issues when they are heavily loaded like in this case where its a main feed.    Evey time I have pulled a bulkhead connector apart the mains have always looked a little stressed.   When I in there I usually take the time to clean them and pinch the female ends down a bit for a little more grip.   I think they could have doubled those up or used a different style larger terminal for the main feeds but they never did.   I think the cars changed around 81 but trucks stayed that way till 88. 

[bcroe]

However...  I am now concerned about why the wire fried instead
of the fusable link. I would suggest having your mechanic replace
the fusable link just to prevent what can be an even bigger issue
in the future.

As I see it, the purpose of fuseable links (and fuses) is blow instead
of allowing an over current situation to fry the wiring.  The original
failed lug here seems to be caused not by over current, but old age. 

The old car wiring was never designed to last decades, no precious
metal contacts or moisture proof connectors.  A connection will
begin to oxidize, and its resistance increases.  If carrying a lot of
current, it will start to heat up, then the process snowballs.  I have
seen this many times in high current circuits of my own cars.  My
usual fix is cut out the failed connector, then solder and shrink tube
the wires together.  If a connector must be retained, I try to find a
waterproof version in my collection, and/or OX-GARD them together. 

Its a credit to the mechanic who was able to work through this and
correct the faults.  Not so much the body shop, but they didn't
cause a wiring failure.  But they also failed to make proper repairs. 
Bruce Roe

[DeVille68]

good! Thanks for posting the solution.