Heated Seats, Testing
Heated seats, testing
NOTE: If voltage on terminal "30" measured by the A/C control head -E87- drops below 12.5 volts, the performance of the heated seats is reduced and the generator load is reduced (the electronic of the A/C control head -E87- reduces the activation from 100% to 90% to 10%).
Checking temperature sensor
Special tools and equipment
- V.A.G 1598 A test box and V.A.G 1598/11 adapter cable and V.A.G 1598/12
- VAS 5051 Vehicle Diagnostic, Testing and Information System with VAS 5051/7 test leads
- V.A.G 1594 A connector test kit
- Switch ignition off.
- Remove A/C Control Head -E87-.
- Connect V.A.G 1598 A test box with V.A.G 1598/11 adapter cable to connector -C-. Connecting VAG 1598/22 Test Box
- Connect V.A.G 1598/12 adapter cable to connector -D- (use a second V.A.G 1598 A test box or connect tester directly to V.A.G 1598/12 using suitable test leads from V.A.G 1594 A connector test kit. Connecting VAG 1598/22 Test Box
NOTE: The terminal assignment of connector -C- on V.A.G 1598/11 adapter cable and connector -D-on V.A.G 1598/12 adapter cable is identical with the socket assignment on V.A.G 1598 A test box.
- Measure resistance between terminal 5 in connector -C- (to Drivers Heated Seat Temperature Sensor -G59-) and terminal 16 in connector -D- (Ground connection) on the test boxes.
- Specification: Resistance greater than 1.5 kohm and smaller than 25 kohm(depending on the temperature of the temperature sensor, at seat temperature of 20 degrees C the measuring value is at approx. 10 k ohm)
- Measure resistance between terminal 6 in connector -C- (to Passengers Heated Seat Temperature Sensor -G60-) and terminal 16 in connector -D- (Ground connection) on the test boxes.
- Specification: Resistance greater than 1.5 kohm and smaller than 25 k ohm (depending on the temperature of the temperature sensor, at seat temperature of 20 degrees C the measuring value is at approx. 10 k ohm)
NOTE:
- The resistance value of the temperature sensor in the heating elements changes with the temperature (the specifications in the following table are approximate values).
Temperature Resistance value of
at temperature sensor temperature sensor
in seat in degrees C in kohm
20 10
30 6.0
40 4.2
50 2.8
60 1.7
- If the resistance value is too large, check and eliminate open circuits or contact resistance in wiring connection to heating elements of heated seats. If open circuit is in seat, repair seat.
Checking heating elements
Special tools and equipment
- VAS 5051 Vehicle Diagnostic, Testing and Information System (with current clamp)
- V.A.G 1594 A connector test kit
Test requirement:
- All fuses OK:
- Switch ignition off.
- Remove A/C Control Head -E87-.
- Disconnect connectors -D-and -F- from A/C control head -E87-
- Connect adapter cable V.A.G 1598/12 of test box to disconnected harness connector -D-.
- Connect V.A.G 1598 A test box to V.A.G 1598/12 adapter cable
- Measure voltage between terminal 3 of connector -F- and socket 13 (Ground connection) of test box.
- Specification: approx. battery voltage
- Measure resistance between terminal 1 of connector -F- and socket 13 (to heating element in drivers seat) of test box.
- Specification: Resistance approx. 1.5 - 2.5 (25) Ohm
- Measure resistance between terminal 2 of connector -F- and socket 13 (to heating element in passenger seat) of test box.
- Specification: Resistance approx. 1.5 - 2.5 (25) Ohm
NOTE:
- Through contact resistance on different connector, resistance values of approx. 25 ohm can be measured. The contact resistance is lowered as soon as a voltage of 12 volts is applied and the function of the heated seats is not affected.
- The resistance value of the heating elements in the seat changes with the temperature (at seat temperature of 20 degrees C the resistance value is approx. 1.9 ohm).
- Resistance values smaller than 10 ohm. cannot be measured accurately with shop tools, a short circuit in the wiring connection or in the heating elements of the heated seats cannot be detected
- If the resistance value is too large, check and eliminate open circuits in wiring connection to heating elements of heated seats. If open circuit is in seat, repair seat.
- Connect harness connectors -D- and -F- to A/C control head -E87- (all connectors are now connected to the -E87-).
- Guide wire of connector -F-terminal "1" through current clamp 50 A of VAS 5051/9.
- Select operating mode "Test instrument" on VAS 5051: Current 50 A current clamp on.
- Bring both thumbwheel for heated seats (on -E87-) to position "0".
NOTE: All harness connectors on A/C control head -E87- must be connected.
- Start engine.
- Move thumbwheel for heated drivers seat to position "6".
- Specification: The display will change from approx. 0 amps to less than 10 amps.
- Move thumbwheel for heated drivers seat to position "0".
- Specification: The display will change from approx. 10 amps to less than 0 amps.
- Guide wire of connector -F-terminal "2" through current clamp 50 A of VAS 5051/9.
- Move thumbwheel for heated passenger seat to position "6".
- Specification: The display will change from approx. 0 amps to less than 10 amps.
- Move thumbwheel for heated passenger seat to position "0".
- Specification: The display will change from approx. 10 amps to less than 0 amps.
NOTE:
- The current probe may be influenced by stray current which could cause the display to show a low current reading when the heated seat is switched off.
- If an open circuit or short circuit exists in the connection to the temperature sensor in the seat, the output to the heating element is not switched by the A/C control head -E87-.
- The A/C control head -E87- does not switch on the heater, if a short circuit to Ground in the heating element or the wiring connection exists (the heater is switched off immediately as soon as a large current flows).