1990 Ford Bronco Instrument Cluster Troubleshooting 60-9 - Voltmeter & Warning
Reference · 1987-1991 BroncoAll 95 service procedures
Shop manual troubleshooting chart (60-9) covering voltmeter low/high voltage and always-on engine warning indicator; check shorts on 39 R/W or open 31 W/R wire.
Part of 1987-1991 Ford Bronco Service Procedures
This document is page 60-9 of a Ford service manual section covering the Instrument Cluster, presenting a continuation of a troubleshooting hints table. The table is organized into three columns: Condition, Possible Cause, and Action. Three conditions are covered: (1) voltmeter indicates low voltage/no voltage, with causes including low battery voltage, wiring/connector faults, a damaged printed circuit, a blown fuse, or an inoperative voltmeter, and matching corrective actions such as servicing the battery/charging system, checking wiring and connectors, inspecting the printed circuit, servicing shorts and replacing fuses, or replacing the voltmeter; (2) voltmeter indicates high voltage, caused by high battery voltage or an inoperative voltmeter, corrected by servicing the charging system or replacing the voltmeter; and (3) Engine Warning Indicator always on, caused by actual high coolant temperature or low oil pressure, a short to ground on the 39 (R/W) wire or an open on the 31 (W/R) wire, an inoperative Coolant Temperature Sender or Oil Pressure Switch, or an inoperative Engine Warning Indicator Module. Detailed diagnostic steps are given, including disconnecting and jumpering the 39 (R/W) and 31 (W/R) circuits to isolate the faulty component before replacing the module.
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Frequently asked questions
- Why does my voltmeter read low or no voltage?
- Per the table, possible causes are low battery voltage, wiring and/or connector faults, a damaged printed circuit, a blown fuse, or an inoperative voltmeter. Actions include servicing the battery/charging system, checking wiring for breaks and connectors for tightness/corrosion, checking the printed circuit for cracks, servicing the circuit short and replacing the fuse, or replacing the voltmeter.
- What causes the voltmeter to indicate high voltage?
- Either high battery voltage (service the charging system as required) or an inoperative voltmeter (replace the voltmeter).
- Why is the Engine Warning Indicator always on?
- Possible causes: an actual high coolant temperature or low oil pressure condition, a short to ground on the 39 (R/W) wire or an open on the 31 (W/R) wire, an inoperative Coolant Temperature Sender or Oil Pressure Switch, or an inoperative Engine Warning Indicator Module.
- How do I test whether the Oil Pressure Switch is causing the warning light to stay on?
- Re-connect the 39 (R/W) wire to the Coolant Temperature Sender, then jumper the 31 (W/R) wire from the Oil Pressure Switch to ground. If the indicator goes off, replace the Oil Pressure Switch.
- What wire colors are used for the Engine Warning Indicator circuits?
- Circuit 39 is R/W (red/white) to the Coolant Temperature Sender and circuit 31 is W/R (white/red) to the Oil Pressure Switch.
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