LEMON Manuals: Even more car manuals for everyone
Home >> Porsche >> 2001 >> 911 Turbo, Automatic >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heater, Diagnosis - 911 Turbo (996) >> Fault code 28 >> Diagnosis/troubleshooting

Fault code 28: Diagnosis/troubleshooting

FAULT CODE 28 DIAGNOSIS PROCEDURE

Work instruction Display OK If not OK
1 Visual inspection
  • Switch off ignition
  • Remove connector for temperature mixing valve
Check the connector for corrosion and that it is correctly inserted
Step 2
Clean connector or plug in correctly
-> End
2 Check 5 V - supply line to temperature mixing valve motor
  • Switch on ignition
  • Measure voltage at plug of the temperature mixing valve between pin 3 and ground
  • Measure voltage at plug of the temperature mixing valve between pin 3 and pin 1
approx. 5 V
Step 3
Step 6
3 Check signal line and servo motor line for short to B+
  • Switch off ignition
  • Remove plug B from the air-conditioning system regulator
  • Measure voltage at plug B of the air-conditioning system regulator between pin 13 and ground
  • Measure voltage at plug D of the air-conditioning system regulator between pin 10 and ground
  • Measure voltage at plug D of the air-conditioning system regulator between pin 2 and ground
0 V
Step 4
Repair wiring hamess
-> End
4 Check signal line and servo motor line for short to gound
  • Measure resistance at plug B of the air-conditioning system regulator between pin 13 and ground
  • Measure resistance at plug D of the air-conditioning system regulator between pin 10 and ground
  • Measure resistance at plug D of the air-conditioning system regulator between pin 2 and ground
Step 5 Repair wiring hamess
-> End
5 Check signal line and servo motor line for interruption
  • Switch off ignition
  • Remove plug B from the air-conditioning system regulator
  • Measure resistance between plug B on the air-conditioning system regulator pin 13 and plug on temperature mixing valve pin 2
  • Measure resistance at plug D of the air-conditioning system regulator between pin 10 and ground
  • Measure resistance at plug D of the air-conditioning system regulator between pin 2 and ground
< 5
Step 10
Repair wiring harness
-> End
6 Check 5 V supply lead for short to B+
  • Remove plug B from the air-conditioning system regulator
  • Switch on ignition
  • Measure voltage at plug B of the air-conditioning system regulator between pin 20 and ground
0 V
Step 7
Repair wiring hamess
-> End
7 Check 5 V supply line for short to ground
  • Measure resistance at plug B of the air-conditioning system regulator between pin 20 and ground
Step 8 Repair wiring hamess
-> End
8 Check 5 V supply line and ground line for open circuit
  • Measure resistance between plug B on the air-conditioning system regulator pin 20 and plug on temperature mixing valve pin 3
  • Measure resistance between plug B on the air-conditioning system regulator pin 9 and plug on temperature mixing valve pin 1
< 5
Step 9
Repair wiring hamess
-> End
9 Check ground line for open circuit
  • Measure resistance between plug B on the air-conditioning system regulator pin 9 and plug on temperature mixing valve pin 1
< 5
Step 11
Repair wiring hamess
-> End
10
  • Repace servo motor for footwell/defrost flap
-> End
11
  • Replace air-conditioning system regulator
->End