Preliminary Diagnosis

Glow plug system preliminary diagnosis should be performed only after ensuring that glow plug system is correctly installed. Check that all connectors are properly installed and that all connections are clean and tight.

This procedure is used to determine if a problem exists in the glow plug system itself, or elsewhere in the electrical system. This procedure should always be completed before performing ELECTRICAL SYSTEM DIAGNOSIS .

1. Connect ammeter in series with Red or Orange wire at top of glow plug controller to left and right banks of glow plugs. Operate glow plug system and note ammeter reading.
2. On pickups, reading must be at least 55 amps. On vans, reading must be at least 50 amps. If ammeter reading is within specification, glow plug system is operating correctly. If ammeter reading is not within specification, one or more glow plugs is inoperative.
3. Check individual glow plug leads by connecting ammeter in series with Green wire. Operate glow plug system. On pickups, each glow plug wire should read about 14 amps. On vans, reading is about 13 amps.
4. If ammeter readings are as specified, glow plugs and wiring are okay. If reading was less than specified, check for continuity by disconnecting glow plug lead and connecting a 12-volt test light from connector to ground. Operate glow plug system.
5. If test light glows, wiring is okay. Replace glow plug(s). If test light does not glow, repair or replace harness. Retest glow plug(s) for proper operation.