Headlights worked a couple weeks ago, but because it's summer and my wife doesn't drive the car at night, we didn't notice that both headlights were out.
Checked:
- Bulbs: Good
- Headlight switch: Good, I think (see below)
- Lo/Hi beam relay (the one in the engine compartment): Good. Switches and latches fine and continuity is as it should be on the relevant terminals.
- Headlight relay: The main suspect, but it's a $60 part that I would rather not spend money on if I can avoid it. It's also deep inside the bowels of the console, and I don't have much weekend left to go diving for it. I couldn't hear it click when I switched the headlights on, but then again it's DEEP in there.

Symptoms: Key in position II, headlight switch position -
- 1 (off) No headlights, no instrument cluster lights.
- 2 (parking) No headlights, parking lights (yellow lights on front corners) on, instrument cluster lights on.
- 3 (headlights and parking lights) No headlights, no parking lights, no instrument cluster lights.
Pulling the Hi/Lo beam lever doesn't momentarily switch Hi beams on in any position.
Same when the car is on and running.

Details on the headlight switch:
- In position 1, there is no continuity between any terninals.
- In position 2, there is continuity between terminals 3 and 7
- In position 3, there is continuity between terminals 1 and 4

IPD sells a replacement for ~10 bucks that has 6 terminals at 1,2,3,4,5, and 7 (6 is an empty slot), but mine only have 4 at 1,3,4, and 7 (slots 5, 6, and 2 are empty). Do I simply have the wrong type?
On the plug, I noticed that 5 spots have terminals, and there are wires attached to all. I didn't think to check the terminal numbers when I had it out, and not sure I want to open it up again just for that, but I thought I'd mention it.

I saw posted elsewhere (brickboard, maybe?) that if the headlight relay goes out, you should be able to pull the Hi/Lo beam stick and get Hi beams momentarily if the switch is still good. If the switch is bad, you won't; but the switch appears to be good. What's next? Go ahead and get the relay? Switch too? Further troubleshooting?

 

I seem to remember that on some 240s there is a headlamp relay located near/under/above the left dead pedal - subject to corrosion/water damage. Sorry don't have a wiring diagram for that car - but I would look for a a simple square bosch relay near there.

 

I've heard of that, but apparently, since 1989(?), it's been buried deep behind the console. I pulled every relay I could find from the old Volvo that finally got towed away, but missed that one. Now I know why...
See the first section here, and the video:
https://www.240turbo.com/headlightrelay.html
The guy in the video shows how deep the relays are buried, and he says the replacement is a "single-throw" relay, but it's more than that: It's a Double Pole Single Throw. O' Reilly has "Import Direct" ones for $60; I'd rather get genuine Bosch from IPD or Amazon even, for 1/4 the price.
I just find it curious that the high beams don't come on at all, when everything I've read so far says that they will unless your switch is bad. My switch is not bad.

 

To get more clues take some voltage measurements. The head light and relay terminals are a good place to start. Measure with respect to chassis ground and record on a sketch of each connector.
It would also help to do one set of measurements when the lights are working (if possible) and another set when they are not.

 

Today the lights are back on. I have no clue what is going on. I didn't do anything. I hate intermittent problems...

 

After digesting this for a couple days, I think I might open up the console, find the relay, and do the ol' un-plug/re-plug tango to re-seat all the connections, with a good helping of anti-corrosion paste. If the socket has melted, I can get a replacement from Prancing Moose.
If that doesn't do it, I'll chase down the wires looking for broken wires or rubbing that's created a short.
That's this weekend's project, I'll report back on Monday...

 

Found the relay, it was behind the brake pedal, don't know how I missed it before. All tested good, but the plug was melted on the power terminal, as suspected, creating a bit of difficulty for the power to get through. I chipped away the melted part to expose the terminal and bent the tangs down a bit for better contact. I have ordered a new plug housing and a spare relay for good measure from Dave at Prancing Moose.

I noticed the high beams weren't coming on, and the Lo/Hi beam relay still worked, so I may have a bad switch in the stem. I just did a test, and indeed, it is very intermittent. I'll get a high beam after flicking the thing 3-4 times. I looked replacement prices, and the best price I can find is almost $300. Maybe I should string that wire out to a momentary switch on the dash or something. Or is there a way to rejuvenate that switch? Cruise control and turn signals work just fine.
I'm now really wishing I had taken that off the old car...