Changes by last author:
Changed:
| A/C Control plans |
| A/C Control |
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We have a universal pressure-switch in the high-pressure tube (after compressor), with 2 blue, and 2 black-green wires, the AC guy told that:
* blue-blue : closed between 2.5 and 28bar. Suitable to enable the relay that enables clutch, and turns the radiator fan (which also draws air through the AC condenser) at low fan-speed * blackgreen - blackgreen : "high-pressure switch" closed above 18 bar: Suitable to turn the radiator fan on at high power through a 70A relay NOTE: now, after they filled the system with R134A gas, the blue-blue is normally open (with engine off). The blackgreen-blackgreen is normally closed (with engine off). This suggests the AC guy was wrong with the wire colors of the universal switch. |
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We have a universal pressure-switch in the high-pressure tube (after compressor), with 2 blue, and 2 black-green wires:
* Normalpressure ( blackgreen - blackgreen ) : closed between 2.5 and 28bar. Suitable to enable the relay that enables clutch, and turns the radiator fan (which also draws air through the AC condenser) at low fan-speed * Above18bar (blue-blue): "high-pressure switch" closed above 18 bar: Suitable to turn the radiator fan on at high power through a 70A relay NOTE: now, after they filled the system with R134A gas (with engine off), * blue-blue is normally inf Ohm * blackgreen-blackgreen is normally 0 Ohm |
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* the ECU should
** disable compressor at max TPS |
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* the ECU can use a miscoutput to
** disable compressor at max TPS (or whatever condition the user finds appropriate, eg. also at low TPS for cars without idle-valve) |
| ** after disabled, do NOT enable for 20 seconds (to prevent compressor clutch wear and belt abuse) |
| ** TODO: after disabled, do NOT enable for 20 seconds (to prevent compressor clutch wear and belt abuse) |
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** the AC compressor clutch (needs +12V)
** the radiator fan at partial power (appr 20A current) through a 2x 0.2 Ohm series resistor that I found under the coolant radiator |
| ** the AC compressor clutch (needs +12V) |
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Radiator fan (on low-power) relay, or a 2nd circuit of the above relay
* original plan was to switch radiator and AC clutch by same 1 circuit relay (the AC main 30A relay). However the AC clutch +12V control line MUST NOT be directly connected to the fan (low-power point in the fan resistor pack): ** When the fan turns on for some other reason (coolant temperature too high), we do NOT want the AC clutch to turn on !!! => separate relay (output) needed ** the output of this relay (circuit) is the radiator fan at partial power (appr 20A current) through a 2x 0.2 Ohm series resistor that I found under the coolant radiator |
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MembersPage/PaulF - also should disable A/C if pressure is too low (method depends on type of pressure sensor). For vehicles without IAC valve it would be useful to be able to disable A/C at a speed/pedal point (to prevent engine stall) |