Testing engine speed adaption when air conditioner cuts in — AUDI

Notes:

The air conditioner sends a positive signal to contact 10 on the engine control unit.
This positive signal is only sent when the air conditioner has an increased power requirement ("AC-High" setting).

Test conditions

Air conditioner functioning properly
No faults recorded in air conditioner fault memory
Interior temperature more than +15 °C
Rear window heating switched off

Connect fault reader V.A.G 1551 (V.A.G 1552) and select engine electronics control unit with the "Address word" 01. When doing this the engine must be running at idling speed.
(Connecting fault reader and selecting engine electronics control unit => Page
01-3
.)

Rapid data transfer
HELP
Select function XX
Indicated on display:

Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Read measured value block
Enter display group number XXX
Indicated on display:

Press keys 0, 5 and 0 to select Display Group 50 and confirm entry with Q key.

Read measured value block 50
⇒
1
2
3
4
Indicated on display:

Check display value for idling speed adaption.

Display zones
1 · 2 · 3 · 4
Display Group 50: Signals to engine control unit
Display · xxx rpm · xxx rpm · A/C-Low · Compr. OFF
Indicates · Actual engine speed / (in steps of 10 rpm) · Specified engine speed / (in steps of 10 rpm) · Air conditioner ready · A/C compressor status
Range · min.: 630 rpm / max.: 2250 rpm · min.: 650 rpm / max.: 1800 rpm · A/C-Low / A/C-High · Compr. OFF / Compr. ON
Specification · xxxx rpm · xxxx rpm · A/C-Low · Compr. OFF / Compressor off
Note · Engine speed readout same as in display zone 2 (±50 rpm) · Fixed value from engine control unit

Switch on the air conditioner by pressing the "Auto" key. The compressor should run.
Set air conditioner to maximum hot/cold air output (display zone 3).

Display zones
1 · 2 · 3 · 4
Display Group 50: Signals to engine control unit
Display · xxxx rpm · xxxx rpm · A/C-High · Compr. ON
Indicates · Actual engine speed / (in steps of 10 rpm) · Specified engine speed / (in steps of 10 rpm) · Air conditioner ready · A/C compressor status
Range · min.: 630 rpm / max.: 2250 rpm · min.: 650 rpm / max.: 1800 rpm · A/C-Low / A/C-High · Compr. OFF / Compr. ON
Specification · Engine speed readout same as in display / zone 2 (±50 rpm) · Fixed value from / engine control unit · A/C-High · Compr. ON / Compressor on
Note · If readout does not match specification, test wiring between air conditioner and engine control unit

Switch off ignition.

Test wiring:

Connect test box V.A.G 1598/22 to wiring harness for engine control unit => Page
24-22
.
Test for open circuit and short to earth or positive in wiring between air conditioner and contact 10 on engine control unit.

=> Current flow diagrams, Electrical fault finding and Fitting locations binder

If there are no faults in the wiring, test operation of air conditioner.

=> Heating, air conditioner; Repair Group 01; Self-diagnosis for air conditioner
Heating, air conditioner
Self-diagnosis for air conditioner