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Boys,
Self-adjusting orifice tube or Volvo orifice tube?
I mean, you can vacuum out the R12 and oil and do this instead if you don't find a 93 to lift the metric fittings from...
https://parts.smithvolvo.com/p/Volvo__240/Conversion-kit/42863163/9145666.html?
Everything fits with some creativity!
Are you putting a whiteblock in your 940?
Getting it to fit involves poking 4 holes on the uprights of the core support and bending some thin sheetmetal 75 degrees. Hardly a drastic change. Just checked last night in fact
I'm still working on retrofitting a '93 system into my '85 (fuel pumps and seats took priority).
There are 4 main functions within the orifice tube AC system:
1) When the snowflake button is pressed, the main AC relay delays turning on power to the AC system for a few seconds after turning on the car. This prevents trying to start with the compressor engaged. The AC system power also automatically runs the cabin heater box fan on low to prevent icing up the evaporator.
2) The pressure switch on the accumulator turns on and off the compressor clutch - high pressure turns on compressor.
3) The pressure switch by the orifice tube turns on and off the front cooling fan relay - high pressure turns on cooling fan relay.
4) The ECU gets signals for AC Button On and Compressor Clutch Engaged. I'm assuming these are used to bump up the idle and spark advance as needed to prevent idle from dropping when the compressor kicks in.
I read that 91-92 got the improved HVAC set up prior the switch to r134.
Curious to see how your project plays out.
Correct, very similar except for the fittings were metric and they did not get a parallel flow condenser.
Sorry, I didn't understand your diagram -- is there a relay that MS turns on to enable&power AC? If so, the easiest is to wire the accumulator switch in series to the compressor clutch from the relay. You need the relay, the clutch takes ~4amps (and the fan takes 8 to 15 amps)Thanks for the feedback. Here are my answers:
1) My ECU has a time delay function built in, so no need for the timed relay. As for the fan switch, my circuit disables the AC request signal from reaching the ECU (which in itself drives the +12v to the compressor) unless the blower fan is on.
2) OK in that case I should revise the diagram and put the accumulator switch in line with the +12v from ecu to compressor
3) In that case I'll just bypass this one altogether. The e fan is also controlled by ecu, as on whenever the AC signal request is present.
4) I think this is the case as well. My MS3X box handles that out of the box also, through one of the spare input signals that I reserved for it.
Let me know whether that all makes sense.