2000 V70 SE / 270K miles / B5422S Denso / AW-5

About to undertake the next project:
Splice in new headlight pigtails (available from ipd) to replace crumbling wires/insulation in the headlamp socket compartment. This job is long overdue; had a blown fuse lately because of electrical short in the now-bare wiring.

I'd like to get upstream enough in the harness to cut out then resplice all of the rotten wire. It looks like the headlight housings (front grille too?) need to be removed to do the splicing job.

Any experience with this procedure out there?

Actually, the wiring was much more damaged than foreseen. For background, on this car (2000 V70) Daytime Running Lights (DRL) are always on, and Sylvania SilverStar H7 headlamp bulbs are used for both Low and High beam.

The LH headlamp was repaired today; will do the RH headlamp later this week.

With the headlamp unit removed from the car and upon inspection, the wiring insulation on all wires had rotted and shed away, resulting in bare wires all the way up to the three-pin connector that plugs into the car's wiring harness. There are four 18 ga. (maybe smaller; 20 ga.) headlamp wires inside the housing: two Brown feed wires, one White wire (high beam), one Yellow wire (low beam).

The touching bare wires as they merged into the three-pin connector were the cause of the electrical shorts and fuse-blowing. The proper repair would have been to repin the three-pin connector with new wires and terminals. I didn't have the pin removal tool nor male terminals for today's job; maybe for next time when I can fully prepare.

To get around the wiring and repinning job for today and with the headlamp assembly on the bench, the bad wires were cut out, leaving enough bare copper wire strands to repair with new insulation. For insulation instead of electrical tape, I used 3 mm heat shrink tubing on each wire, which provided a viable insulation covering all the way into the three-pin connector. Then, new ipd sockets w/pigtails were solder-spliced, one for High beam and one for Low beam.

Then, reinstalled the headlamp assembly, plugged in the harness, new fuses (15A, one each for High and Low), and there are now fully working headlights; no shorts.

My guess is likely the combination of always-on DRL, SilverStar bulbs and 20 years ultimately completely damaged the wiring insulation in that small, confined and high-heat bulb chamber.

Will test drive the car tonight !

Most of the damage to the wiring will be inside the headlight housing where the heat is contained. Before you go 'wild', wait until you get the 2 new connectors.
--
Keeping it running is better than buying new

Have you seen this rotten wiring with your own eyes or are you just assuming it's rotten?

The cheap plastic socket for the H7 lamps crumbling apart isn't the only thing happening.

The female parts of the connection (the ones in the socket that the blades of the H7 go into) loosen. This results in an ineffective connection. You get more heat. Lots of times you get scorching and blown fuses.

On 4 of these cars I've simply cracked away the cheap plastic socket body, pinched the female connectors a bit with pliers to increase bite and plugged the light back in. It doesn't matter which wire goes on the bulbs' blades as a filament light bulb isn't polarized.

In all these cases blown fuses was a symptom.

The structure and length of the connector keep the wires separated every time. They actually cannot short.

As I recall there has never been a case where the wire insulation was even involved. The insulation always looked good.

If indeed you have cracked insulation I'd consider doing a neat electrical tape job.

I add a THIN wipe of silicone grease to the bulbs' blades to ease assembly.

Honestly, try that first.

I too bought a replacement socket and I've never needed it. I just did what I described above. I bet it'd work the same for you. Don't go nuts cutting back into the car's wiring. It VERY LIKELY isn't necessary.