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OK, Nathan has an accumulator with a cycling switch on it. looks like correct adjustable switch. no wires on it at all. so this i believe is his current issue.
Last edited by derekderek; Feb 4, 2022 at 08:02 AM.
Here is what I see now that I have looked a little more into the VIR eliminator cycling switch.
The new cycling switch takes the place of your original Low Pressure cutoff Switch.
The original wiring size is #16 gauge or 1.0 sqmm metric.
Cut 2 lengths of #16 wire or 1.0 sqmm (different colors) long enough from the original plug of Low Pressure Cutoff to your new cycling switch.
Need 2 male 1/4" crimp connectors 2 F/M crimp connectors.
Jumper wires:
1. Connect the Tan wire Male side to original low pressure switch plug Tan wire side.
Connect F/M side to one side of your new cycling switch.
2. Connect Lt.Green Male side to original low pressure switch plug Lt.Green wire side.
Connect F/M side to the other side of your new cycling switch.
The cycling circuit is now wired to compressor.
the cycling switch is a low pressure cut-off that is on the low side. bypassing it for a few seconds to get refrig in is one thing. running it that way will freeze up the evaporator.
the cycling switch is a low pressure cut-off that is on the low side. bypassing it for a few seconds to get refrig in is one thing. running it that way will freeze up the evaporator.
You are NOT bypassing it, you are using it as the switch...
From Classic Auto Air...
The adjustment screw is located between the terminals on the switch.
The screw must be turned APPROXIMATELY 3/4 of a turn COUNTER CLOCKWISE.
This will bring the cycle-off pressure down to 21 psi, which is needed for R134a.
I believe these switches are factory set for R12, that is why the 3/4 turn CCW if using 134a.
I am saying that bypassing is a baaad idea. And don’t ask me how I know! And you must buy an R12 adjustable switch as R134 switches are a different larger thread.
Here is what I see now that I have looked a little more into the VIR eliminator cycling switch.
The new cycling switch takes the place of your original Low Pressure cutoff Switch.
The original wiring size is #16 gauge or 1.0 sqmm metric.
Cut 2 lengths of #16 wire or 1.0 sqmm (different colors) long enough from the original plug of Low Pressure Cutoff to your new cycling switch.
Need 2 male 1/4" crimp connectors 2 F/M crimp connectors.
Jumper wires:
1. Connect the Tan wire Male side to original low pressure switch plug Tan wire side.
Connect F/M side to one side of your new cycling switch.
2. Connect Lt.Green Male side to original low pressure switch plug Lt.Green wire side.
Connect F/M side to the other side of your new cycling switch.
The cycling circuit is now wired to compressor.
This type of miss information I also found. No! this is incorrect. Set up like this if the condenser can't cool fast enough high side pressures will build! You need a binary switch in place of the low pressure switch and it absolutely needs to be wired in as I outlined above.
Just to satisfy my curiosity, in the L77 on system is it possible for the high side pressure to get to dangerous levels without the thermostatic switch turning off the compressor?
Without fans running, Yes. The stock system assumes that the fan (mechanical) always runs. When changing over to electric fans. If the fans are not running the condenser can't do its job and pressures will build.
Thus a safety switch is a very good idea and a trinary switch will kick on the fans when pressure hits 220. even if the engine hasn't reached temp for the fans to kick on yet.
I really want to understand...
Ok, I get the safety concerns without replacing the original Low pressure cutoff switch with a Binary Switch, that is Crystal Clear .
Let's use your wiring diagram...
Does this sound right?
Cycling Switch S1 Contacts set to open at 21psi No power to Binary Switch. 21psi as per Classic Air Instructions using R134a.
Binary Switch S2 Low pressure Contacts open at or around 30psi Compressor Shuts Off. 30psi as per Vintage Air.
So any pressure above 22psi at Accumulator Cycling Switch contacts close sending power to Binary Switch.
If Binary Switch Low Pressure Contacts are satisfied (Above 30psi Contacts Closed) Compressor Starts.
If Binary Switch High Pressure Contacts reach at or above 406psi (Contacts Open) Compressor Shuts Off.
I think I understand now why you said it dosen't matter if Cycling or Binary switches are wired first, two completely different pressure values.
This would be True for the VIR eliminator upgrade system only.
Yes 2 different pressures, but also keep in mind the direction of flow of the freon. It goes through the condenser then down the liquid line reaching the binary switch first. pressures at the binary switch are not affected by the cycling switch. the cycling switch affects pressures going into the evaporator.
Yes 2 different pressures, but also keep in mind the direction of flow of the freon. It goes through the condenser then down the liquid line reaching the binary switch first. pressures at the binary switch are not affected by the cycling switch. the cycling switch affects pressures going into the evaporator.
Yes, High Pressure Liquid at the Binary, +30psi contacts closed.
Once High Pressure Liquid passes through the Orifice adapter block, it changes to Low Pressure Liquid, or that is how I understand it.
Here is a diagram from the Factory service manual. Perhaps this will help you understand. Note that we have high pressure from the bottom of the condenser to the factory VIR. Then low pressure after the VIR. now we are removing the VIR and replacing it with a accumulator and a orifice block. But the pressure thing is the same. The cycling switch is to control the pressure past the accumulator. Not before it. So without the binary switch if the condenser can't cool quickly enough pressures will build in that liquid line.
Whoa! There is a huge amount of info here. I appreciate you all sharing.
I’ve now got the wiring correct, but noticed that one of the pipes to the accumulator was basically not done up. So sorted that out as well.
Ive found a local air con guy who understands these setups and who is willing to help me step by step. So first step now the wiring is done is to recharge the system and see where a leak might be. I am then going to get the binary switch fitted and make the decision whether it’s worth the extra cost to replace the evaporator that I’ve purchased or run with the one installed. (Which I don’t think was an original one and was replaced in AUS)
As I said, thank you for the information. It has helped me understand the setup better than the hours and hours of research which got me nowhere. I am sure this thread will continue to be viewed in future as well.
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