Glow Plug Controller

1985 Chevrolet Suburban C10, 6.2 CSECTION Glow Plug Controller

A faulty controller/relay assembly may result in excessive white smoke in exhaust and/or poor idle immediately after starting. The following procedure checks for proper operation of controller circuit.

NOTE: Engine coolant temperature must be below 80°F (27°C) before beginning test.
  1. Turn ignition to "RUN" and allow glow plugs to cycle. Wait 2 minutes, then turn ignition to "CRANK" for 1 second and back to "RUN". Glow plugs should cycle on at least once. If glow plugs do not cycle as described, proceed to step 2.
  2. Disconnect controller connector. Connect 12-volt test light between harness connector terminal "B" (Purple wire) and ground. With ignition in "RUN" position, test light should be off. With ignition in "CRANK" position, light should be on.
  3. If test light does not operate as described, repair short or open in engine harness Purple wire. If light operates properly but glow plugs did not cycle in step 1, replace controller.
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

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.