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240 Air Conditioning Retrofit

I don’t have an orifice tube in my older setup but, when I was researching updating to the 91-93 system everyone said go with self adjusting.
 
You can buy AC flush in a compressed can at most Auto Parts store. Ive use it several times on my system then I used compressed air through the whole system.
 
A quart of A/C flush at NAPA is $35. It took 2 cans of brake cleaner at $2.50 each to do the same thing. The condenser is the most difficult part. Fill it with the liquid and slosh that around in a removed unit then blow it out with compressed air.
 
Boys,

Self-adjusting orifice tube or Volvo orifice tube?

Per the UK wizards on the 700/900 Maint pages (Volvo Klub UK) they strongly recommend the variable OT. I paid the $36 for mine which is sleeping in the 940 as it is being repainted.... and also winter season in NW GA. Per the Klub..... the VOT makes all the difference in traffic and stop/go conditions; no real benefit at highway speeds. I dont recall if I took a pic of the P/N in my build thread or not.... too long ago.

So NOW you are going complete '93 system in your early vehicle..... which Wren declares for which the condenser doesn't fit with butchery? I'm still holding my full 93 system for my 242.... awaiting to see your photos of "making it fit".......
 
The condenser bolts right in after drilling a few holes. I have a complete 93 system in my 80 245.
 
I have the 1976 242 apart now and have done the heater core and blower motor. I want the AC to work so do I have to get the AC core from a 93 in there or can I use that from the 1976 and change everything else? I wanted to do the rough in if you will and finish hooking it up in the summer.

...michael
 
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 :-P
 
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 :-P

Yep, this. I went to Park Rose hardware and bought nice new isolators and bolted mine right in a few months ago.
 
Here is my idea of an AC circuit built around my PWM heater fan and MS3X, with the 1993 diagram below. Feel free to chime in. I'm assuming that the sensor at the accumulator is a simple pressure switch and not a fancy variable signal sensor.


Yes I am aware that my handwriting is atrocious:

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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'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.

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.

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.
 
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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.
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)

The 940s use a different scheme for the compressor. Instead of a switch that closes at high pressure to turn on the fan, the 940s use a switch that opens at high pressure. The 940s then wire the accumulator switch in series with the over pressure switch to the compressor clutch. Normally, the accumulator switch turns on and off the compressor. If high pressure it too much, the high pressure switch opens and the compressor stays off until the pressure drops.

I'll post some pics of my '93 condenser into '85 sheet metal later -- I used 4 home depot nailing plates, and a bunch of bolts/screws to extend the condenser frame to the the sheet metal. Pretty simple once I figured out how to do it.
 
Quick update on the diagram: I will redraw what I ended up doing. I have zero formal training in designing electrical circuits so bear with me. Duane, I have some more detailed shots for you now. I drilled a total of 4 7mm holes and used a combination of donut type isolators and rubber cushion mounts, plus high temp weatherstrip foam to seal the cooling package. 1850CFM SPAL fan is barely cutting it in terms of cooling the engine. Might throw the 1000CFM fan in the front location as a pusher. If that fails I will revert to the stock 940T fan as it moves 4500 CFM on its own according to internet lore. We shall see.

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