Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 4.3 W, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)QUICK LOOKUPSELECTRICAL COMPONENT LOCATIONSELECTRICAL COMPONENT LOCATORSWITCHES
1999 GMC Forward Control 4.3 W, Standard
Electrical Component Locator: Switches
1999 GMC Forward Control 4.3 W, StandardSECTION Switches
SWITCHES
| Component | Component Location |
|---|---|
| A/C Compressor High Pressure Cut-Off Switch | On rear of A/C compressor. |
| A/C Compressor Refrigerant Pressure Switch | On A/C accumulator (body builder installed). |
| Auxiliary Engine Coolant Fan A/C Pressure Switch (Motor Home) | In A/C compressor high pressure line (body builder installed). See Figure. |
| Back-Up Lamps Switch (M/T) | On left side of transmission. |
| Brake Pressure Differential Switch (Commercial Van) | Internal to electronic brake control module. |
| Brake Pressure Differential Switch (Motor Home) | Internal to electronic brake control module. See Figure. |
| Clutch Pedal Position Switch | On top of clutch pedal support. |
| Cold Advance Solenoid Engine Coolant Temperature Switch | On rear lower portion of right cylinder head, near exhaust manifold. |
| Engine Coolant Level Switch (Commercial Van) | On left lower end of radiator surge tank. |
| Engine Coolant Level Switch (Motor Home) | On right lower end of radiator surge tank. See Figure. |
| Evaporative Emissions (EVAP) Canister Purge Vacuum Diagnostic Switch (5.7L VIN R) | On right side of engine. |
| Evaporative Emissions (EVAP) Canister Purge Vacuum Diagnostic Switch (7.4L VIN J) | On left side of engine. |
| Park Brake Actuator Position Switch (Motor Home) | In auto apply park brake component box at right frame rail behind transmission. See Figure. |
| Park Brake Indicator Switch | On parking brake lever (body builder installed). |
| Park Brake Pressure Indicator Switch (Motor Home) | In auto apply park brake component box at right frame rail behind transmission. See Figure. |
| Park Brake Pull Button Switch | Mounted to dash. |
| Park Brake Pump Motor Switch (Motor Home) | In auto apply park brake component box at right frame rail behind transmission. See Figure. |
| Park Brake Switch (W/O Auto Apply) | On I/P harness (body builder installed). |
| Park/Neutral Position (PNP) & Back-Up Lamps Switch | On left side, near middle of transmission. |
| Power Brake Booster Fluid Flow Indicator/Alarm Delay Switch | Behind left radiator support (body builder installed). |
| Power Brake Booster Pump Pressure Switch | Behind left radiator support (body builder installed). |
| Stoplights Switch (Motor Home) | At brake pedal support. See Figure. |
| Torque Converter Clutch (TCC) & Stoplights Switch (Commercial Van) | At brake pedal support. See Figure. |
| Torque Converter Clutch (TCC) & Stoplights Switch (Motor Home) | At brake pedal support. See Figure. |
RENDER: 1.0x
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.