Check Power Supply And Ground Circuit

WARNING: This page is about a different car, the 2013 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

Check power supply circuit.
1. Disconnect the seat heater switch.
2. Turn the ignition switch to ON.
3. Measure the voltage between harness connector terminal and chassis ground.
  Connector & terminal
  
  (R43) No. 7 (+) - Chassis ground (-):
  
  Is the voltage 12 V or more?
  - Yes → Go to step 2 .
  - No → Check the harness between the seat heater switch and fuse.
Check ground circuit.
Measure the resistance between harness connector terminal and chassis ground.

Connector & terminal

(R43) No. 2 - Chassis ground:

Is the resistance less than 10 Ω?
- Yes → Go to step 3 .
- No → Repair the harness.
Check ground circuit.
Measure the resistance between seat heater switch terminals.

Connector & terminal

(R43) No. 7 - (R43) No. 2:

Is the resistance less than 10 Ω?
- Yes → The power supply and ground circuits are normal.
- No → Replace the seat heater switch.