Since it started immediately after a rainstorm, do you notice water pooling anywhere in the cabin or elsewhere?

You might want to find a Subaru specialist near you; the member recommended list is here.

 

Finding electrical problems is the same for any car made. So your mechanic is afraid of electrical diagnostics, or he doesn't understand electrical diagrams, or it's an excuse that it's a Subaru and he doesn't want to mess with it.

First check is at the light socket. You can use a cheapo test light to check for power and ground. Power is provided to the bulb via the BIU and ground by the light switch.

Do you have single bulb or 2 bulb headlights? Wiring is different between the 2 types. The 2 bulb light has a low and a high beam bulb. The single uses 1 large bulb with 3 wires.

Is the high beam indicator on all the time? The indicator is connected to the RH bulb.

Did the mechanic change any wiring at the light to control the light, and if so, what did he do?

There is a separate fuse for each headlight. The fuse box under the hood has a diagram of the fuses and both fuses are next to each other.

If the LH light is working, you can discount a switch issue.

 

Thanks so much. I think my mechanic is unfamiliar with Subarus and feels uneasy poking around too much. This is the first finicky problem the car has had, so he has just done basic stuff.

What you suggested sounds good, but impossible for a non techy type like me to follow. (I am an 83 year old professional gardener with zip car fixit smarts.)
Sadly, I am in Canada, but thanks for reaching out.

 

Loose electrical connections between the motor and modules that let water in will trigger random blinking lights on the dash. It happened to me. My brown connector looked ok, but it wasn't fully connected.
Lighting, if it's just one light, and no blown fuses, look at it's local wires. One is likely broken, loose, or corroded. If it's a group of lights, and no blown fuses check the switches. They wear and sometimes need replaced. Even if there are blown fuses, this would indicate there is likely an exposed wire shorting somewhere and would need to be found and corrected anyway.

 

Thanks sio much for the response. This sounds very promising. We drove through heavy rain with huge ponding on the road. So if water got at any loose connections I guess that would do it.
Unfortunately, I lack the tech expertise to troubleshoot. I think I have to get an actual Subaru mechanic to look. Sadly all the ones I knew and trusted have left.

 

With some luck, the stuff will dry on its own in time and dry warm weather. Unfortunately, I'm sure that is scarce right now in your parts.

 

With some luck, the stuff will dry on its own in time and dry warm weather. Unfortunately, I'm sure that is scarce right now in your parts.

With some luck, the stuff will dry on its own in time and dry warm weather. Unfortunately, I'm sure that is scarce right now in your parts.

We had hoped leaving it out in the sun for hours post the rain event, would dry it out. and of course, as you mentioned, not much sun or heat for us right now. Hubby says he will attempt to follow some of the ideas posted here.

 

That signature shows up on every one of my post and it states, "If you are in Austin, TX.......". There's 3 Subaru dealers within 40 miles of each other and they all suck. Many people in this forum have had trouble with misdiagnosis or guesswork. So I put that there so people can see it.

If you were in Austin, is probably dinsrhe problem within 5 minutes. It's most likely at the bulb socket or the wires to it. That's if the fuse is good and the light doesn't work.