PTC Heater Circuit Troubleshooting
  1. Check the No. 26, 27, 28 (40 A) fuses in the under-hood fuse/relay box, and the No. 36 (10 A) fuse in the under-dash fuse/relay box.
Are the fuses OK?
YES -
Go to Step 2 .
NO -
Replace the fuses and recheck. If the fuses blow again, check for a short in the No. 26, 27, 28 (40 A) and No. 36 (10 A) fuses circuit.■
  1. Disconnect the PTC heater core 7P connector.
  1. Turn the ignition switch ON (II).
  1. Measure the voltage between the PTC heater core 7P connector terminal No. 1 and body ground.
Is there battery voltage?
YES -
Go to Step 5 .
NO -
Repair open in the wire between the under-hood fuse/relay box and the PTC heater core. If the wire is OK, replace the under-hood fuse/relay box. ■
  1. Turn the ignition switch OFF.
  1. Check for continuity between body ground and the PTC heater core 7P connector terminals No. 4, 5, 6, and 7 individually.
Is there continuity?
YES -
Go to Step 7 .
NO -
  1. Turn the ignition switch ON (II).
  1. Measure the voltage between the climate control unit 32P connector terminal No. 17 and body ground.
Is there battery voltage?
YES -
Go to Step 9 .
NO -
Repair open in the wire between the under-hood fuse /relay box and the climate control unit. If the wire is OK, replace the under-hood fuse /relay box. ■
  1. Measure the voltage between the PTC heater core 7P connector terminal No. 3 and body ground.
Is there battery voltage?
YES -
Go to Step 10 .
NO -
Repair open in the wire between the under-hood fuse/relay box and the PTC heater core. If the wire is OK, replace the under-hood fuse/relay box. ■
  1. Measure the voltage between the climate control unit 32P connector terminal No. 18 and body ground.
Is there battery voltage?
YES -
Go to Step 11 .
NO -
Repair open in the wire between the under-hood fuse/relay box and the climate control unit. If the wire is OK, replace the under-hood fuse /relay box. ■
  1. Measure the voltage between the PTC heater core 7P connector terminal No. 2 and body ground.
Is there battery voltage?
YES -
Go to Step 12 .
NO -
Repair open in the wire between the under-hood fuse/relay box and the PTC heater core. If the wire is OK, replace the under-hood fuse /relay box. ■
  1. Measure the voltage between the climate control unit 32P connector terminal No. 19 and body ground.
Is there battery voltage?
YES -
Go to Step 13 .
NO -
Repair open in the wire between the under-hood fuse/relay box and the climate control unit. If the wire is OK, replace the under-hood fuse/relay box. ■
  1. Substitute a known-good climate control unit, and recheck.
Is the symptom goes away?
YES -
Replace the original climate control unit .■
NO -
Replace the PTC heater core.■