Rear Window Will Not Defog
WARNING: This page is about a different car, the 1997 Mercury Mountaineer and 1997 Ford Explorer. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
This test is associated with DTCs B1342, B1347 and B1349.
- Check Ignition PID
Using New Generation Star (NGS) scan tester or equivalent, access Generic Electronic Module (GEM). Check IGN PID data while turning ignition switch to each position. If PID values agree with actual switch positions, go to next step. IF PID values disagree with actual switch positions, repair Black/Pink wire between ignition switch and GEM. - Check DTCs
Retrieve DTCs from GEM. For additional information on code retrieval procedure, see MODULE COMMUNICATIONS NETWORK article. If no DTCs are displayed, go to next step. If DTC B1347 or B1349 are displayed, go to next step. If DTC B1343 is displayed, go to step 13). If DTC B1342 is displayed, replace GEM and retest system. - Check Rear Defog Relay PID
Using NGS scan tester, access GEM. Turn ignition on. Check RDEFRLY PID data. Toggle active command RLY CNTRL ON and OFF. If RDEFRLY PID data agrees with command from scan tool, go to step 10). If PID data indicates OFFO-G, go to next step. If PID data indicates ON-B-, go to step 8). - Check Power To Rear Defogger Relay
Remove rear defogger relay (located in upper right side of dash near glove box). Measure voltage between ground and pin No. 4 (Purple/Orange wire) at defogger relay harness connector. See Fig 1. If battery voltage exists, go to next step. If battery voltage does not exist, check fuse No. 26 in interior fuse panel. If fuse is okay, repair open Purple/Orange wire. If blows repeatedly, repair shorted Purple/Orange wire. - Check Rear Defogger Relay
Remove rear defogger relay. Test relay. See REAR DEFOGGER RELAY under COMPONENT TESTING . Replace relay if necessary. If relay is okay, go to next step. - Check Orange/Yellow Wire
Turn ignition off. Disconnect 18-cavity harness connector from GEM (in center of dash). Measure resistance of Orange/Yellow wire between GEM module pin No. 16 and defogger relay harness connector. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open Orange/Yellow wire and retest system. - Check Orange/Yellow Wire For Short
Measure resistance between GEM module pin No. 16 (Orange/Yellow wire and ground. If resistance is less than 10 k/ohms, repair short to ground in Orange/Yellow wire. If resistance is greater than 10 k/ohms, replace GEM. - Check Rear Defogger Relay
Remove Rear defogger relay. Test relay. See REAR DEFOGGER RELAY under COMPONENT TESTING . Replace relay if necessary. If relay is okay, go to next step. - Check Orange/Yellow Wire For Short To Power
Turn ignition off. Disconnect 18-cavity harness connector from GEM. Turn ignition on. Measure voltage between Orange/Yellow wire between GEM module pin No. 16 and ground. If any voltage is indicated, repair short to power in Orange/Yellow wire and retest system. If no voltage is indicated, replace GEM and retest system. - Check Power To Switch
Remove fuse No. 32 from interior fuse panel. Using scan tool, access GEM. Using active command, turn defogger RLY CNTRL to ON. Measure voltage between fuse No. 32 cavity and ground. If battery voltage does not exist, go to next step. If battery voltage exists, install fuse and go to step 13). - Check Power To Relay
Turn ignition off. Remove rear defogger relay. Measure voltage between defogger relay harness connector pin No. 5 (Gray/Light Blue wire) and ground. See Fig 1. If battery voltage exists, go to next step. If battery voltage does not exist, check fuse No. 14 (30-amp maxi-fuse) in power distribution panel. - Check Rear Defogger Relay
Remove Rear defogger relay. Test relay. See REAR DEFOGGER RELAY under COMPONENT TESTING . Replace relay if necessary. If relay is okay, repair Brown/Light Blue wire between defogger relay and fuse cavity No. 32. - Check RDEF_SW PID
Monitor RDEF_SW PID while pressing and hold down rear defogger switch. If RDEF_SW PID indicates ON when pressed and held and OFF when released, go to step 17). If switch position and PID do not agree, go to next step. - Check Ground To Switch
Turn ignition off. Disconnect rear defogger switch. Measure resistance between Black wire at rear defogger switch harness connector and ground. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open ground (Black) wire. - Bypass Switch
Monitor RDEF_SW PID data. Connect a jumper wire between rear defogger switch harness connector pins No. 3 (Dark Blue/Orange wire) and No. 4 (Black wire). See Fig 2. If RDEF_SW PID indicates ON, replace rear defogger switch and retest system. If RDEF_SW PID indicates OFF, go to next step. - Check Dark Blue/Orange Wire For Open
Turn ignition off. Disconnect 26-pin harness connector from GEM located in center of instrument panel. Measure resistance of Dark Blue/Orange wire between rear defogger switch connector pin No. 3 and GEM harness connector pin No. 1. If resistance is less than 5 ohms, replace GEM. If resistance is greater than 5 ohms, repair open Dark Blue/Orange wire. - Check Power To Grid
Disconnect defogger grid power harness connector at back window. Turn ignition on. Using scan tool, command defogger RLY CNTRL ON. Measure voltage between defogger grid connector and ground. If battery voltage exists, go to next step. If battery voltage does not exist, repair open Brown/Light Blue wire changing to Black wire between rear defogger relay and defogger grid connector. - Check Grid Ground Circuit
Measure resistance between ground connector at rear defogger grid and ground. If resistance is less than 5 ohms, repair defogger grid or replace rear window. If resistance is greater than 5 ohms, repair open ground wire. Chassis ground point is on upper/left portion of liftgate.