[328.lover]

My n52 developed a bouncing idle randomly only with the AC on. It fluctuates between 800 to 550rpm when idling while the AC is on. It's not effecting driving but it's just a jerky idle, no codes or lights or anything. Put in new coils and sparks less than 20k miles ago. No idea what could've caused this randomly, ac clutch, idle air control valve? Help please

[gaze2]

Maybe a failing AC clutch?

[gbalthrop]

Originally Posted by 328.lover

My n52 developed a bouncing idle randomly only with the AC on. It fluctuates between 800 to 550rpm when idling while the AC is on. It's not effecting driving but it's just a jerky idle, no codes or lights or anything...

Your US Model N52 (Mo/Yr UN-stated) has NO compressor Clutch. The compressor uses a "Compressor Valve" to control pumping of refrigerant by the compressor. If Idle RPM ONLY varies (is "irregular") when Green LED on "Snowflake" button at right of IHKA Panel is lit, then RPM irregularity occurs when "Compressor Valve" causes R-134a refrigerant to be pumped, resulting in increased power requirement to turn compressor pulley.

There is a "Refrigerant Pressure Sensor" on the "High Side" R-134a line between the Condenser & Evaporator coils. If System Pressure gets too high for some reason (or too low), the signal from that Pressure Sensor will cause compressor valve to stop compressor pumping of refrigerant. There are a Number of things that can cause Compressor Valve intermittent operation:
1) Radiator Fan NOT running at idle & compressor ON, resulting in excessive High Side Pressure;
2) Wiring issues;
3) Pressure Sensor issues;
4) Refrigerant charge too High/ Low.

INPA (BMW Factory-Level Diagnostic Software) can display "Live Data" of Refrigerant Pressure Signal as received by JBE/IHKA Modules & can also display Evaporator Temp that shows if compressor is pumping. INPA can also Activate Radiator "E-Fan", and show % of Max Speed of Fan.

So HOW YOU can Diagnose the issue depends upon what equipment you have, & WHAT Model. Please answer the following:

1) What are Last-7 Characters of VIN? Mo/Yr built?
2) What Make/Model Scan Tool or Diagnostic Software (INPA/ISTA) do you have available? Can that Tool "Connect" to JBE Module or IHKA Module?
3) You say "no codes or lights": Can tool used to read "codes" connect to either JBE Module or IHKA Module? DME (Engine Control Module) are NOT helpful here, and there are 15+ other Modules in vehicle BESIDE DME.
4) What Fault Codes are read in JBE (Junction Box Electronics) & IHKA (climate Control) Modules?
5) Does Radiator E-Fan run when A/C & Compressor "Snowflake" active?
6) Has any work been done in Engine Compartment prior to this issue beginning? Any Refrigerant added or vented?

With answers to those Questions we can suggest "Next Steps".
George