I have my dash apart and found evidence of heat damage on the relay socket (green/red wire) The lights work, but I am wondering if I should replace the socket while I have ready access. If so, what is the best source for one where I could unplug and replug the factory wires? Also, what causes it to get so hot?
thanks

You need to replace the terminal, not the plastic housing. Just nibble away the plastic housing where it is charred, cut off the terminal as far back as you can without having to splice more length in, and put a new terminal on the wire. The cause is invisible oxidation which increases the contact resistance which in turn generates heat, relaxing the spring contact force, causing further oxidation, and completing the tail-chasing cycle.

If you really want to put a new housing around the terminals, check davebarton.com for relay socket housings and I'm sure he will have terminals and crimpers.

Excuse the pics of the much easier job this was when this relay was located under your feet instead of behind the center vents.




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Art Benstein near Baltimore

Two antennas met on a rooftop--, The wedding was O.K., but the reception was great!

Thanks so much for the quick response and elegant solution. Also, very helpful to me was your description of the oxidation as "invisible". I have on hand some "deoxit" spray cleaner; I think that I will give all of the connections a quick spray and a thin layer of dielectric grease while I'm at it. Is this a good practice?

Yes. DeoxIT D-Series spray, or concentrate (dilute with 91% Isopropyl Alcohol, or another compatible residue-free carrier solvent to dilute) that you can use in small, accurate sprayer.

The liquid form, when the carrier solvent evaporates, the DeoxIT-D active compound(s) remain on the conductor contact surface. Read the product copy for a description.

https://caig.com/deoxit-d-series/

Do NOT use electrically conductive, corrosion inhibiting paste like No-OX and De-OX and the like meant for high current (amps), high power (volts), AC and DC systems.

I thought there was a DeoxIT-D dielectric grease. I guess not?

Some extra info, lest you know already.

The 1986+ US DOT 240 headlight are wholly awful. The beam pattern is not well defined. The lens material can fog on both surfaces - exterior and interior. Also, headlight alignment can go wonky. Though the adjustment is a frail affair at the assembly backside accessed through the hood up engine bay.

The adhesive between lens and reflector body embrittles and loses adhesion, so the lens and reflector body separate, allowing moisture and detritus intrusion. A hot halogen bulb encountering liquid can explode inside the headlight assembly, ruining what may be a salvageable assembly. You may see the ugly end result as yellow headlight lenses that disallow proper headlight beam casting. The light should pass though the lens clearly. (Punny. ha.) I've already written here how to clean and seal the headlight assemblies somewhere.

At the bottom center edge of the lens, use a finger to gently pull and lift the lens.

When I get a 240, not since 2007 or or so, I treat all connectors and grounds with a connect / reconnect (or slight unscrew / re-screw ) at collected grounds secured to sheat metal) with Deoxit-D. So, rarely do I encounter the invisible corrosion like that at the fuse panel back side that disabled power windows in the 1990 240 wagon in 2015 or so.

Questions?

Hope that helps.
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Give your brickboard.com a big thumbs up! Way up! - Roger Ebert.

When (what year) did the terminal and relay move behind the center vents?

And for a real longterm fix, also at Dave Barton's site there is information about how to use a relay on each side of the car to deliver the current needed to drive the bulbs. Then only a tiny amount of current (enough to engage the relays) will move through the factory wires/switches/connectors. An added benefit will be brighter/more light out of the headlights.
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82 242-6.2L; '17 Mazda3; '16 Crosstrek