AC - signal unclear: Diagnosis/troubleshooting

NOTE: After troubleshooting, a system test must be carried out!

DIAGNOSIS/TROUBLESHOOTING (FAULT CODE 30, AS OF MY 2002)

Work instruction			Display OK	If not OK
1	Visual inspection	Ignition on Switch the fresh-air blower on Check if air flows out	Step 2	Step 12
2	Check the power supply for the air conditioning compressor	Ignition off Pull off fuse C 5 Allow engine to run in idle state Measure voltage between fuse C 5, pin A 9 and ground	>11 V Step 3	Step 6
3	Check line between relay for magnetic coupling and air-conditioning system regulator for open circuit	Ignition off Remove connector B from the air-conditioning system regulator Pull connector from the magnetic coupling Disconnect relay for magnetic coupling Measure resistance between relay socket pin 5 and air-conditioning system regulator connector B pin 16	< 2 Step 4	Repair wiring harness -> End
4	Check line between relay for magnetic coupling and magnetic coupling for open circuit	Ignition off Measure the resistance between relay socket pin 5 and magnetic coupling connector	< 2 Step 5	Repair wiring harness -> End
5	Checking the magnetic coupling	Ignition off Measure resistance between magnetic coupling and ground	Approx. 3 to 5 (at23°C)	Step 23
5	Checking the magnetic coupling	Using a suitable auxiliary cable and an interconnected fuse (7.5 A) briefly connect the magnetic coupling with battery positive connector (terminal 30) one time (< 1 second) and disconnect again	Magnetic coupling switches audibly Step 24	Step 23
6	Check line between relay for magnetic coupling and air-conditioning system regulator for short circuit to ground	Ignition off Pull connector from the magnetic coupling Measure resistance between relay socket pin 5 and ground	Step 7	Repair wiring harness -> End
7	Check activation on relay for magnetic coupling	Ignition off Reconnect connector B to the air-conditioning system regulator Push connector onto magnetic coupling Connect fuse C 5 Allow engine to run in idle state Switch on air-conditioning Measure voltage between relay socket pin 2 and ground	Between 0 V und 12 V Fluctuating approx. 3 times per second	Activation of DME missing Repair wiring harness, or carry out diagnosis DME -> End
		Measure voltage between relay socket pin 7 and ground	> 11 V	Power supply from DME relay pin 5 interrupted Repair wiring harness -> End
		Measure voltage between relay socket pin 3 and ground	> 11V	Step 8
		Ignition off Measure resistance between relay socket pin 4 and ground	< 2 Step 21	Open circuit between relay for magnetic coupling and ground point 8 Repair wiring harness -> End
8	Check power supply of relay for fresh-air blower	Ignition off Remove connector from pressure switch Ignition on Measure voltage between pin 4 and ground on pressure switch connector	> 11 V Step 9	Open circuit between VS 65 and pin 4 of pressure switch connector Repair wiring harness -> End
9	Check pressure switch	Ignition off Measure resistance at the pressure switch between pins 1 and 4	< 2 Step 10	Step 11
10	Check line between pressure switch and relay for magnetic clutch for open circuit	Ignition off Measure resistance between connector at pressure switch pin 1 and relay socket for magnetic coupling pin 3	< 2 -> End	Repair wiring harness -> End
11	Check refrigerant pressure		Step 20	Repair system and fill -> End
12	Check activation on relay for fresh-air blower	Ignition off Remove relay for fresh-air blower Measure resistance between relay socket pin 2 and ground	< 2	Open circuit between relay for fresh-air blower and ground point 3/1 Repair wiring harness -> End
		Ignition on Measure voltage between relay socket pin 2 and ground	< 0.3V	Open circuit to B+ between relay for fresh-air blower and ground point 3/1 Repair wiring harness -> End
		Ignition on Measure voltage between relay socket pin 3 and ground	>11 V	Step 14
		Ignition on Measure voltage between relay socket pin 7 and ground	>11 V Step 13	Step 17
13	Check line between relay for fresh-air blower and load for short circuit to ground	Ignition off Pull connector from fresh-air blower Pull off connector from fan for inside sensor Remove connector from pressure switch Ignition on Measure resistance between relay socket pin 5 and ground	Step 22	Repair wiring harness -> End
14	Check the power supply for the load	Ignition off Remove fuse D 6 Check fuse D 6	Fuse OK	Replace fuse Step 16
14	Check the power supply for the load	Ignition on Measure voltage between fuse holder D pin A 13 and ground	> 11V Step 15	Repair power supply from current distributor -> End
15	Check line between fuse holder D and relay for fresh-air blower for open circuit	Ignition off Measure resistance between fuse holder D, pin A 14 and relay socket pin 3	< 2 -> End	Repair wiring harness -> End
16	Check line between fuse holder D and relay for fresh-air blower for short circuit to ground	Ignition off Measure resistance between relay socket pin 3 and ground	-> End	Repair wiring harness -> End
17	Check the power supply for activation of relay for fresh-air blower	Ignition off Pull off fuse C 7 Check fuse C 7	Fuse OK	Replace fuse Step 19
17		Ignition on Measure voltage between fuse holder C pin A 11 and ground	>11 V Step 18	Repair power supply from current distributor -> End
18	Check line between fuse holder C and relay for fresh-air blower for open circuit	Ignition off Measure resistance between fuse holder C, pin A 14 and relay for fresh-air blower pin 7	< 2 -> End	Repair wiring harness -> End
19	Check line between fuse holder C and relay for fresh-air blower for short circuit to ground	Ignition on Measure voltage between fuse holder C pin A 14 and ground	< 0.3V -> End	Repair wiring harness -> End
20	Replace pressure switch		-> End
21	Replace relay for magnetic coupling		-> End
22	Replace relay for fresh-air blower		-> End
23	Replace magnetic coupling		-> End
24	Replace air-conditioning system regulator		-> End