My front-right corner light has gone from bad to worse. The running light was not working, and now the turn signal light has stopped working (the bulb is new). The right turn signal now flashes at about twice the regular speed, but the front does not light up. I'd like to try re-wiring the fixture. Can anyone tell me where to find the other end of the wire leading to that light?

Before you rewire, and you really don't want to do that, make sure your light is getting power by testing the plug with the parking lights on and/or the flashers on.
Most of the time it is the contact in the light assembly that has corrosion on it and it just needs a through cleaning.
BTW, if you replace one corner bulb, replace the one on the other side also. What else are you going to do with the extra bulb that comes in the package?

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)

When the running light first failed I checked for power to the plug, and found power when the flasher was on, but not when just the lights were on. What does the fast flashing suggest?

For most cars, a fast flasher means one bulb somewhere on that side is burned out or not getting electric contact. 99% of the time it is a contact problem. I suggest you take out the bulb and use an emery stick (fingernail scraper) to clean the contacts in the socket. Maybe do the same to the other bulbs on that side of the car. The sockets have two thin wires that serve as contacts (+ and -), so even a tiny amount or corrosion breaks the current flow.

When these cars were new, I recall many complaints about bad turn signals. Was there a recall? I cleaned one of my turn signals and used some dielectric grease on the bulb, and it has been fine for 5 years.

The fast flashing is a warning that one of the lights is not working, either front or rear.
When you checked for power, did you check it at the connector or the bulb base? If you checked at the base, clean it thoroughly and check it again. If you checked at the plug connector, make sure the wiring is not chaffed where it goes through the fender.

Klaus
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The 164 has a new home, all I am left with are a 95 854T and a 98 V70R :)