Windshield - Heated Cadillac DeVille Concours

DESCRIPTION & OPERATION

Heated windshield is designed to quickly melt ice by applying high voltage to a specially fabricated windshield. Windshield contains a transparent internal conductive coating which heats up when power is supplied to system. Power comes directly from generator (alternator), only while engine is running and system is turned on.

System consists of special windshield, Windshield Power Module (WPM), generator, Windshield Control Module (WCM), and a DE-ICE switch mounted on right half of instrument panel cluster. When system is turned on, Powertrain Control Module (PCM) increases engine idle speed to compensate for charging system drain. If transmission is in Park or Neutral, PCM may increase idle speed to about 1200 RPM.

SYSTEM OPERATION

When WCM senses that DE-ICE switch button has been pressed, WCM grounds fast idle request input from PCM, causing PCM to increase idle speed. While system is on, WCM signals instrument panel cluster to turn indicator light on. WCM sends a signal to WPM, which converts 3-phase AC current (received from generator) into Direct Current (DC).

WCM also acts as system timer, turning heated windshield off after each cycle or disabling system if failure is detected. System does not draw current from battery, but it reduces charging current available to battery.

Special windshield uses conductive film sandwiched between layers of windshield glass. Internal conductive film is heated when power is supplied to system.

Generator (Alternator)

System is powered by a modified version of vehicle's standard generator. Generator has 3-phase terminals to provide AC power to WPM.

Windshield Power Module (WPM)

WPM is mounted in right front fender area. WPM is a transformer that converts 3-phase AC voltage to 50-85 DC volts for use by windshield.

Windshield Control Module (WCM)

WCM is located below instrument panel at right side of steering column, above brake pedal. WCM turns system off at end of each cycle or if system failure is detected. Initial cycle is 4 minutes; repeat cycles are 2 minutes.

TESTING PRECAUTIONS

PRELIMINARY CHECKS

1. Before testing heated windshield system, ensure battery and charging system are functioning properly. Ensure battery terminals and connections are clean and tight. Check for visible windshield system damage.
2. Use a digital volt-ohmmeter capable of reading up to 10 k/ohms. Before performing any other tests, perform the «HEATED WINDSHIELD INOPERATIVE»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated__heated-windshield-inoperative) test.

HEATED WINDSHIELD INOPERATIVE

Note. Before performing this test, read TESTING PRECAUTIONS and perform PRELIMINARY CHECKS .

1. Turn ignition off. Unplug windshield connector. (Scheme 4) On windshield side of connector, measure resistance between terminals "A" (Light Blue wire) and "B" (Red wire).
2. If resistance is 0.6-8.0 ohms, go to next step. If resistance is not 0.6-8.0 ohms, check connector terminals. If terminals are okay, replace windshield.
3. Measure resistance between terminals "B" (Red wire) and "C" (Black wire). If resistance is 2.0-8.0 ohms, go to next step. If resistance is not 2.0-8.0 ohms, check connector terminals. If terminals are okay, replace windshield.
4. Measure resistance between each terminal and ground. If resistance is more than 10 k/ohms, go to next step. If resistance is less than 10 k/ohms, check for shorts or conductive material between windshield and body.
5. Connect windshield connector. Disconnect WCM connector. Measure resistance between ground and terminal A8 (Black/White wire) of WCM connector. (Scheme 5) If resistance is more than 5 ohms, go to next step. If resistance is less than 5 ohms, check for open in Black/White ground wire.
6. Turn ignition switch to RUN position. Measure voltage between ground and terminal A6 (Light Green wire) of WCM connector. If voltage is more than 10 volts, go to next step. If voltage is less than 10 volts, check for open in Light Green wire between WCM and fuse block.
7. Start engine. Measure voltage between ground and terminal B6 (Orange wire) of WCM connector. If voltage is more than 10 volts, go to next step. If voltage is less than 10 volts, check for open in Orange wire between WCM and fuse/relay center.
8. Press and hold DE-ICE switch. Measure voltage between ground and terminal A3 (Dark Blue wire) of WCM connector. If voltage is more than 5 volts, go to next step. If voltage is less than 5 volts, check for open in Dark Blue wire between WCM and instrument panel cluster. If wire is okay, diagnosis instrument panel cluster. See «INSTRUMENT PANEL»(/cadillac/deville-concours/1994-1998/remont/gauges-instrument-panels/#instrument-panel) article.
9. Shift gear selector to Park or Neutral. Measure resistance between ground and terminal B3 (Orange/Black wire) of WCM connector. If resistance is less than 10 ohms, go to next step. If resistance is more than 10 ohms, check for open in Orange/Black wire between WCM and park/neutral switch. If wire is okay, replace park/neutral switch.
10. Shift gear selector to Drive. Measure resistance between ground and terminal B3 (Orange/Black wire) of WCM connector. If resistance is more than 10 k/ohms, go to «TEST "B"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated). If resistance is less than 10 k/ohms, check for short to ground in Orange/Black wire between WCM and park/neutral switch. If wire is okay, replace park/neutral switch.

Scheme 4

SYSTEM CHECK

Note. Perform SYSTEM CHECK before proceeding to TEST "A" through TEST "G" . Performing tests out of order could result in improper diagnosis and replacement of good components.

1. Turn ignition off for at least 5 seconds. Turn ignition switch to RUN position. If LED does not come on, go to next step. If LED (indicator light) comes on, check for short to ground in Dark Blue wire between Windshield Control Module (WCM) and Instrument Panel Cluster (IPC). If Dark Blue wire is okay, perform «TEST "F"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) .
2. Connect tachometer. Run engine until warm. Note idle speed. Ensure transmission is in Park. Press DE-ICE switch once ( DO NOT press a second time or system will deactivate). If windshield heats up, go to next step. If windshield does not heat up, check to see if LED is on. If LED is not on, perform «TEST "A"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) . If LED is on, perform «TEST "B"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) .
3. Check to see if LED is on. If LED is not on, perform «TEST "D"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) . If LED is on, check idle speed. If idle speed increased, go to next step. If idle speed does not increase, system malfunction exists between WCM and PCM.
4. After 4 minutes, LED should go out and windshield should stop heating. If LED and windshield turn off properly, go to next step. If LED stays on, but windshield turns off properly, perform «TEST "F"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) . If LED turns off properly, but windshield stays on, leave engine running and perform «TEST "G"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) .
5. Press DE-ICE switch again ( DO NOT cycle ignition switch). Heated windshield system should come on for 2 minutes, then turn off automatically. If system operates as described, go to next step. If system does not operate as described, replace WCM.
6. Basic system functions are operating normally. If a no-charge condition is indicated only when heated windshield is turned on, perform «TEST "E"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) . If system is functioning properly, but LED is on at all times, perform «TEST "F"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated) .

WCM Voltage Test

1. Disconnect Windshield Control Module (WCM) connector. Start engine. Measure battery voltage. If voltage is less than 11.2 volts, repair charging system. If voltage is more than 11.2 volts, leave engine running.
2. Measure voltage between ground and terminal B6 (Orange wire) of WCM connector. (Scheme 5) If voltage is less than 11.2 volts, replace faulty fuse and/or repair Orange wire. If voltage is more than 11.2 volts, turn ignition off.
3. Measure resistance between ground and terminal A8 (Black/White wire) of WCM connector. (Scheme 5) If resistance is more than one ohm, repair open Black/White wire. If resistance is less than one ohm, turn ignition switch to RUN position.
4. Measure voltage between ground and terminal A6 (Light Green wire) of WCM connector. (Scheme 5) If battery voltage is present, go to next step. If battery voltage is not present, replace faulty fuse and/or repair Light Green wire.
5. Ensure DE-ICE switch is in OFF position. Connect voltmeter between terminals B6 (Orange wire) and A3 (Dark Blue wire) of WCM connector. (Scheme 5) If zero volts is present, go to next step. If battery voltage is present, check for short to ground in Dark Blue wire. If Dark Blue wire is okay, replace instrument panel cluster.
6. Press and hold DE-ICE switch button. If battery voltage is present, go to «TEST "B"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated). If zero volts is present, check for open Dark Blue wire. If Dark Blue wire is okay, replace instrument panel cluster.

Scheme 5

WCM Output Test

1. Disconnect Windshield Control Module (WCM) connector. Start engine. Connect a 10-amp fused jumper wire between terminals A6 (Light Green wire) and B1 (Yellow wire) of WCM connector. (Scheme 5) CAUTION: DO NOT leave fused jumper wire connected for longer than 4 minutes.
2. If click is heard from Windshield Power Module (WPM), go to step 4). If click is not heard, disconnect fused jumper wire. If jumper wire fuse is blown, repair short to ground in Yellow wire. If jumper wire fuse is not blown, check for open Yellow wire.
3. If Yellow wire is okay, check for open or high resistance in Black wire between WPM terminal "E" and ground. If wire and resistance are okay, replace WPM.
4. Feel windshield. If windshield is not warm, go to next step. If windshield is warm, check for open Light Green wire between WPM and WCM. If Light Green wire is okay, check for open or short to ground in Light Blue wire between WCM and heated windshield. If Light Blue wire is okay, check for poor wiring connection at WCM and WPM. If connections are okay, replace WCM.
5. Turn ignition off. Disconnect heated windshield connector. (Scheme 4) Start engine. With fused jumper wire connected as in step 1), measure voltage between terminals "B" (Red wire) and "C" (Black wire) of heated windshield connector.
6. If voltage is more than 50 volts, go to next step. If voltage is less than 50 volts, check for open Black and/or Red wires between WPM and heated windshield connector. If wires are okay, check for poor wiring connections at WPM. If connections are okay, perform «TEST "E"»(/cadillac/deville-concours/1994-1998/remont/heated-glassdefoggers/#windshield-heated).
7. Check for poor wiring connections at heated windshield connector. If connections are okay, repeat HEATED WINDSHIELD INOPERATIVE test. If symptom still exists, problem is intermittent.

Control Switch (DE-ICE Switch) Test

1. Ensure Windshield Control Module (WCM) connector is connected. Disconnect Black connector C1 from Instrument Panel Cluster (IPC). Turn ignition switch to RUN position.
2. Measure voltage between ground and terminal B8 (Dark Blue wire) of IPC connector C1. If voltage is not 8-10 volts, go to next step. If voltage is 8-10 volts, check for poor wiring connection at IPC. If connection is okay, replace IPC.
3. Check for open or short to ground in Dark Blue wire between WCM and IPC. If wire is okay, check for poor wiring connection at WCM. If connection is okay, replace WCM.

LED (Indicator Light) Test

1. Turn ignition off. Start engine and let idle. Press and release DE-ICE switch. Before 4 minutes passes, disconnect Black connector C2 from Instrument Panel Cluster (IPC). Measure voltage between ground and terminal B10 (Dark Green wire) of IPC connector C2.
2. If about 8.5 volts are not present, go to next step. If about 8.5 volts are present, check for poor wiring connection at IPC. If connection is okay, replace IPC.
3. Check for open or short to ground in Dark Green wire between WCM and IPC. If wire is okay, check for poor wiring connection at WCM. If connection is okay, replace WCM.

Generator Output Test

1. Disconnect 3-phase output connector. (Scheme 6) Run engine at idle. Set AC voltmeter to 20-volt scale (minimum). On generator side of harness, measure AC voltage between terminals "X" and "Y", terminals "X" and "Z", and terminals "Y" and "Z".
2. If 9-14 volts is not present in all 3 cases, replace generator. If 9-14 volts is present in all 3 cases, check for open circuits (including poor wiring connections) between generator and Windshield Power Module (WPM). If circuits are okay, replace WPM.

Scheme 6

LED Short Test (LED Stays On)

Disconnect Windshield Control Module (WCM) connector located below instrument panel, at right side of steering column, above brake pedal. Turn ignition switch to RUN position. If LED turns off, replace WCM. If LED does not turn off, check for short to voltage in Dark Green wire between terminal B10 of Instrument Panel Cluster (IPC) connector C2 (Black connector) and terminal A4 of WCM. (Scheme 5) If Dark Green wire is okay, replace IPC.

System Short Test

Disconnect Windshield Control Module (WCM) connector located below instrument panel, at right side of steering column, above brake pedal. If windshield stops heating, replace WCM. If windshield does not stop heating, measure voltage between ground and terminal B1 (Yellow wire) of WCM connector. (Scheme 5) If battery voltage is present, repair short to voltage in Yellow wire. If battery voltage is not present, replace WPM.

REMOVAL & INSTALLATION

Disconnect and isolate negative battery cable. Remove 2 bolts securing WCM to support bracket located below instrument panel, at right side of steering column, above brake pedal. Remove WCM. Disconnect wiring harness connector. To install, reverse removal procedure.

Disconnect and isolate negative battery cable. Disconnect 3-pin connector in output line between generator and WPM. (Scheme 6) Disconnect WPM connector. (Scheme 7) Remove 4 nuts securing heated windshield bracket to frame stud. Remove 4 lower bolts securing WPM to bracket. To install, reverse removal procedure. Tighten bolts to 13 INCH Lbs. (1.5 N.m).

Scheme 7

Heated Windshield System Wiring Diagram (Concours, DeVille & Seville). Scheme 8

See also:
• COMPUTER RELEARN PROCEDURES
• INSTRUMENT PANEL
• HEATED WINDSHIELD INOPERATIVE
• PRELIMINARY CHECKS
• TEST "B"
• SYSTEM CHECK