How long do the glow plugs heat before the Wait to Start lamp turns off?

The glow plugs are heated from zero to fifteen seconds, depending on engine coolant temperature; then the controller cycling switch opens and turns off the Wait to Start Indicator Lamp.

Where is the Glow Plug Controller located?

It is attached to the top of the engine block, specifically at the LH rear top of the engine (page-figure 43-1).

What should I check if no glow plugs operate?

If there is no voltage at the Y wire connector of the Glow Plug Controller, check Fuse Links B and C and check the wiring.

What causes one glow plug not to operate?

No voltage at the BR wire of the Glow Plug — check for an open in the BR wire.

How long does the After-Glow Timer cycle the glow plugs?

The After-Glow Timer, located inside the Glow Plug Controller, cycles the glow plugs for up to two minutes depending on engine temperature. The Wait to Start lamp does not light during the after-glow period.

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1988 Ford F-250 Diesel Glow Plug Control/Start Circuit - EVTM Page 32

Diesel start/glow plug control circuit operation description page 32 how the circuit works

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Service manual text explaining diesel glow plug control operation: glow plug controller heats plugs 0-15 seconds based on coolant temp, with after-glow timer cycling up to two minutes.

AI caption February 2008 · Photo 6 of 9

This is page 32 of a Ford Electrical & Vacuum Troubleshooting Manual (EVTM) covering the Start/Glow Plug Control/Run circuit for a diesel engine. The "How the Circuit Works" section explains that the solid-state Glow Plug Controller, mounted on top of the engine block, controls pre-glow and after-glow cycles by sensing engine temperature and voltage. With the ignition in RUN, voltage from Fuse Link V powers the controller and the Wait to Start Indicator Lamp; glow plugs heat for 0–15 seconds depending on coolant temperature, and an After-Glow Timer inside the controller cycles the plugs for up to two minutes. The page also notes the diesel uses two batteries for extra starting and glow plug power. A Component Location table lists positions of the Cold Advance Solenoid, Cold Idle Solenoid, Engine Temperature Switch, Fuel Line Heater (page-figure 44-1), Fuel Shut-Off Solenoid, Fuse Links B/C/M (near starter relay), Fuse Links U/V (RH fender apron), Glow Plug Controller (LH rear top of engine, 43-1), Glow Plug Indicator, and Starter Relay. Troubleshooting hints cover no glow plugs operating (check Fuse Links B and C, Y wire) and a single inoperative glow plug (check for open in the BR wire). Part of a multi-page set (pages 30–34).

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Frequently asked questions

How long do the glow plugs heat before the Wait to Start lamp turns off?: The glow plugs are heated from zero to fifteen seconds, depending on engine coolant temperature; then the controller cycling switch opens and turns off the Wait to Start Indicator Lamp.
Where is the Glow Plug Controller located?: It is attached to the top of the engine block, specifically at the LH rear top of the engine (page-figure 43-1).
What should I check if no glow plugs operate?: If there is no voltage at the Y wire connector of the Glow Plug Controller, check Fuse Links B and C and check the wiring.
What causes one glow plug not to operate?: No voltage at the BR wire of the Glow Plug — check for an open in the BR wire.
How long does the After-Glow Timer cycle the glow plugs?: The After-Glow Timer, located inside the Glow Plug Controller, cycles the glow plugs for up to two minutes depending on engine temperature. The Wait to Start lamp does not light during the after-glow period.