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Old 01-11-2019, 04:37 PM   #51
RvolvoR
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Originally Posted by Harlard View Post
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
Yep, this. I went to Park Rose hardware and bought nice new isolators and bolted mine right in a few months ago.
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Old 08-15-2019, 11:46 PM   #52
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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.


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Old 08-16-2019, 01:06 AM   #53
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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.
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Old 08-16-2019, 03:26 AM   #54
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I read that 91-92 got the improved HVAC set up prior the switch to r134.
Curious to see how your project plays out.
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Old 08-16-2019, 03:38 AM   #55
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Quote:
Originally Posted by bobxyz View Post
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.

Quote:
Originally Posted by Otto Mattik View Post
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.

Last edited by Harlard; 08-16-2019 at 09:16 AM..
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Old 08-16-2019, 12:39 PM   #56
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Originally Posted by Harlard View Post
Correct, very similar except for the fittings were metric and they did not get a parallel flow condenser.
Waiting to see your fitment of the 93 one year only condenser.... into the early sheet metal.
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Old 08-16-2019, 02:35 PM   #57
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Check my project thread. It's all in place.
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Old 08-17-2019, 12:36 AM   #58
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Quote:
Originally Posted by Harlard View Post
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.
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Old 09-06-2019, 04:39 PM   #59
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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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Old 09-07-2019, 11:21 PM   #60
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You need a pusher fan for a truly efficient ac
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