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Hi Mike,
Methinks Volvo took a long time to get the 240's AC right because it wasn't a luxury marketed at home in Sweden. I guess the feedback was slow.
Ken is right - that relay is an improvement made as a "running change" in mid-79 model year, and although the principle remained through all later 240 years, the method changed. In 79 they tried to kill two birds with that relay; stalling after starting due to hot compressor head, and evaporator freeze-up when the blower wasn't turned on.
In 79.5-80, the relay delayed AC and gated AC by the blower switch. This means the heater blower must be on, and 10 seconds of alternator D+ output must occur before the compressor is allowed to be switched on by the thermostat control.
In 81, the heater blower function was changed (eliminating term. 86 function on the relay) such that AC no longer depended on the blower motor switch, but the freeze-up was addressed by running the blower in lowest speed whenever the key was on.
Then, best I can tell from my green books, 84 introduced the microswitch at the AC thermostat control, operating the blower at low speed whenever AC was on.
So, there are three relays that I know of, yours being the earliest, with terminal 86. If you can't find a replacement (swapping is always the easiest approach to troubleshooting) can you use some wiring diagrams to be certain you need a relay or give you a way to adapt one of the later versions? Or would schematics of the relay internals (have for all three) help you repair yours?
some ancient history on this trouble here
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Art Benstein near Baltimore
Have an awesome day and know that someone has thought about you today...I did.
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