AIr Conditioning Diagnosis Question
#16
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I have now verified that the clutch on the compressor is not engaging when I command LO on the AC system from the cockpit. Apparently I was being fooled by the engine anticipating a load and responding to that.
How would I verify that the clutch is getting g the correct signal to engage?
How would I verify that the clutch is getting g the correct signal to engage?
#17
Racer
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Thank you. After looking at the schematic in the Bentley's it appears that it's simply 2 wires going to the compressor and I'm guessing that I should measure 12V between the two with the compressor commanded on. Is that correct?
#18
#21
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With the engine running, do a continuity test across both terminals on the switch.
If closed, it's working, if not, then the switch is not closing either due to faulty switch, or not enough pressure.
I would caution against grounding the wires going to any sensor.
That can damage transistors from/to the computer/controller.
I've seen ECUs damaged that way many times.
If closed, it's working, if not, then the switch is not closing either due to faulty switch, or not enough pressure.
I would caution against grounding the wires going to any sensor.
That can damage transistors from/to the computer/controller.
I've seen ECUs damaged that way many times.
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Bush Pilot (02-01-2023)
#22
Racer
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I connected a refrigerant can to the system and that pressurized the system to about 28 psi, hi and lo side, per my uncalibrated Chinese gauges and the compressor did not come on so that more refrigerant would be brought into the system. Would that be enough pressure to trigger the sensor to allow the compressor to come on? Edited: Just realized that that's a dumb question since 28 psi is within the operating range so that should be enough pressure to trigger the low pressure switch to allow the compressor to come on.
Last edited by Bush Pilot; 02-01-2023 at 12:42 PM.
#23
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I couldn't find published anywhere what the low pressure switch trip pressure is. You could try increasing the pressure in your system by putting the refrigerant can in a bucket of hot water. I'm guessing your ambient temperature is around 32F based on the 28psi static pressure reading.
#24
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I connected a refrigerant can to the system and that pressurized the system to about 28 psi, hi and lo side, per my uncalibrated Chinese gauges and the compressor did not come on so that more refrigerant would be brought into the system. Would that be enough pressure to trigger the sensor to allow the compressor to come on? Edited: Just realized that that's a dumb question since 28 psi is within the operating range so that should be enough pressure to trigger the low pressure switch to allow the compressor to come on.
#25
Racer
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Where would I find the pressure switch? From my reading I would expect there to be a high pressure side switch and a low pressure side switch but when I search "air conditioning pressure switch" for my car on Pelican's site only one switch pops up and the description doesn't say what side it is which leads me to believe that I have only one ac pressure switch.
#26
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Where would I find the pressure switch? From my reading I would expect there to be a high pressure side switch and a low pressure side switch but when I search "air conditioning pressure switch" for my car on Pelican's site only one switch pops up and the description doesn't say what side it is which leads me to believe that I have only one ac pressure switch.
Look for the high pressure connection.
It is just in front of it.
Last edited by TexSquirrel; 04-04-2023 at 05:13 PM.
#27
Racer
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Thank you. What about a low pressure switch location?. Since my compressor won’t come on, if it is a pressure switch I’m thinking it would be a low pressure one.
#28
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I'm not certain whether there is a low pressure switch.
I have only seen the high pressure switch when attaching gauges and refilling refrigerant.
I've replaced entire AC systems in other vehicles, but not in a 986 or 986.
BTW, I just checked my wiring diagrams and I found the attached for AC wiring for the 996/997.
The 986/987 should be similar.
Part numbers for most AC components are similar between 986 & 996.
I have only seen the high pressure switch when attaching gauges and refilling refrigerant.
I've replaced entire AC systems in other vehicles, but not in a 986 or 986.
BTW, I just checked my wiring diagrams and I found the attached for AC wiring for the 996/997.
The 986/987 should be similar.
Part numbers for most AC components are similar between 986 & 996.
Last edited by TexSquirrel; 04-12-2023 at 08:42 PM.
#29
Racer
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Thanks so much Tex. You're a lot of help. I've come to the conclusion that there's only one pressure switch in the system. I'm going to do some more troubleshooting this weekend. Time to get this AC working.