Intermittent AC not working/ high idle.

[smittybr]

On my 2017 2.2 TDI I'm still having intermittent issues with my AC compressor not engaging, often paired with a high idle (~1,300 RPM). It's as if the PCM is commanding this for a cold start. I live in a warm tropical area, so it's not cold. I replaced the ECT sensor thinking that it may be faulty, but it didn't change anything. In fact, it was working the last few days, and when I replaced it, it triggered the problem to resurface. I've inspected the nearby harnesses and several more on the engine. I've checked some ground connections around the battery, but does anyone else have any good next steps to try? The refrigerant pressure is right where is supposed to be, and the high idle isn't always present. I'm leaning towards a connectivity issue, or some sensor causing the PCM to tell the compressor not to engage.

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[RangerBill]

On my 2017 2.2 TDI I'm still having intermittent issues with my AC compressor not engaging, often paired with a high idle (~1,300 RPM). It's as if the PCM is commanding this for a cold start. I live in a warm tropical area, so it's not cold. I replaced the ECT sensor thinking that it may be faulty, but it didn't change anything. In fact, it was working the last few days, and when I replaced it, it triggered the problem to resurface. I've inspected the nearby harnesses and several more on the engine. I've checked some ground connections around the battery, but does anyone else have any good next steps to try? The refrigerant pressure is right where is supposed to be, and the high idle isn't always present. I'm leaning towards a connectivity issue, or some sensor causing the PCM to tell the compressor not to engage.

Check for any DTCs with Forscan or a good scanner.

 

[airline tech]

I would check the following:

AC Pressure Sensor (PID) - the request may be being sent and raising the RPMs but the pressure sensor is keeping the clutch disabled

When you checked for the AC Pressure was it with an external manifold gauge set or this PID?
If only a gauge set, the sensor may be reporting invalid pressure data

AC Clutch Field Coil - You can Bi-Direction control it - with KOEO and you should hear it click
The PCM commands the clutch, but it does not engage would possibly cause high idle and no AC

Check AC Clutch Relay - may be sticking

These would be my top 3 to check and you can view all the data with a scan tool and also Bi- direction the control for testing and there are also (True / False) PIDs for
AC Inhibited due to - xx
Note: Forscan is limited in these types of PIDs, you may need a high-end scan tool to see them

I would also check the following

The Engine RPM's Desired PID when the engine is at the high idle this will help determine if the PCM is actually commanding it

 

[smittybr]

I would check the following:

AC Pressure Sensor (PID) - the request may be being sent and raising the RPMs but the pressure sensor is keeping the clutch disabled

When you checked for the AC Pressure was it with an external manifold gauge set or this PID?
If only a gauge set, the sensor may be reporting invalid pressure data

AC Clutch Field Coil - You can Bi-Direction control it - with KOEO and you should hear it click
The PCM commands the clutch, but it does not engage would possibly cause high idle and no AC

Check AC Clutch Relay - may be sticking

These would be my top 3 to check and you can view all the data with a scan tool and also Bi- direction the control for testing and there are also (True / False) PIDs for
AC Inhibited due to - xx
Note: Forscan is limited in these types of PIDs, you may need a high-end scan tool to see them

I would also check the following

The Engine RPM's Desired PID when the engine is at the high idle this will help determine if the PCM is actually commanding it

I would check the following:

AC Pressure Sensor (PID) - the request may be being sent and raising the RPMs but the pressure sensor is keeping the clutch disabled

When you checked for the AC Pressure was it with an external manifold gauge set or this PID?
If only a gauge set, the sensor may be reporting invalid pressure data

AC Clutch Field Coil - You can Bi-Direction control it - with KOEO and you should hear it click
The PCM commands the clutch, but it does not engage would possibly cause high idle and no AC

Check AC Clutch Relay - may be sticking

These would be my top 3 to check and you can view all the data with a scan tool and also Bi- direction the control for testing and there are also (True / False) PIDs for
AC Inhibited due to - xx
Note: Forscan is limited in these types of PIDs, you may need a high-end scan tool to see them

I would also check the following

The Engine RPM's Desired PID when the engine is at the high idle this will help determine if the PCM is actually commanding it

Perfect, I will check these things as well. Thank you. I have bypassed the relay and the AC clutch kicks in just fine when given power.

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