I used to remodel homes and have done quite a lot of new electrical work in the past with that said I need some advice on how to proceed with this old work issue we just moved into a house that has 1980's wiring but, some age related electrical issues - primarily loose connections have developed.

Currently i have replaced a majority of the outlets (only kitchen and the bathroom outlets left) I have found numerous pigtail connections with blackened wires but no indication of burnt insulation.
we had a short the other night when my wife turned off the ceiling fan light it knocked out three of the five upstairs light fixtures

The shorted fixtures appear to be wired in series and the closet light fixture must have shorted and blackened the box along with some of the drywall so i turned off the breaker to that line and I am trying to decide whether I should replace the whole line from the breaker box or just go through all of the fixtures and replace the wire nuts and tighten all of the connections.


Pulling the wire from the basement will be a pain but if it is the safest thing to do I will do it.

 

You probably don't need to pull new wires or cables.

Clean up and tighten up all of the connections.

Easier said than done; you need to check them all. Remove all electrical tape. For each wire nut that was really loose you should remove it and make sure the wire ends are clean bright copper before refastening. A wire nut or comparable fastener is always needed; just twisting and taping will not do.

You may see bare ground wires just twisted together in each box. These too need to have a wire nut added. Also add a short length (pigtail) to the ground wire cluster to reach the green screw of each switch or receptacle in the box.

Note that if insulation is cracking off the wire end from having been charred then you have to snip off that portion of the wire end and work from there which can be a bit tricky.

If only the end is charred but the insulation on the wire looks good going back into the wall then the wiring inside the wall is not damaged.

You don't have any shorts (if you did not trip any breakers or see any spots where not only did insulation chip off but also bare wires touched and melted). You have "opens" which are the result of loose connections finally coming apart.

Nothing was (nothing should have been) wired in series like old fashioned and modern miniature Christmas tree lights. But a loose connection will break a daisy chain with the result that several other fixtures and receptacles (downstream) can go dead.

Loose connections generate a lot of heat which is why you saw charred areas and items. Many fires over the years and decades and century have resulted from loose connections.

If you see a (rare) soldered connection with no sign of overheating or charring, you do not have to take that one apart. Just retape it.