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Ford expert, ASE Certified Technician
Category: Ford
Satisfied Customers: 10370
Experience:  30 yrs,experience shop owner,
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Glow plug light on the dash wont come on

Resolved Question:

Glow plug light on the dash won't come on. Sometimes when I turn the ignition on it will briefly barely light up and then go out. Other times it rapidly flashes. How does the system work? 1995 Ford F250 7.3L turbo diesel.
Submitted: 7 years ago.
Category: Ford
Expert:  Ford expert replied 7 years ago.

hi , this is commonly a bad controller or bad glow plugs here are a few tests to do and let me know what you find,

Tests/Procedures:1. Check the wiring harnesses from the glow plug controller to the glow plugs. Verify when the glow plugs are on that the voltage drop between them is less than 0.5v.

2. Check the resistance of the glow plugs when cold. Good glow plugs will be around 0.5 ohms, usually will not be less than 0.2 ohms or more than 1.0 ohm. If the resistance is not correct, replace the glow plugs and recheck the operation.

3. If the glow plugs and wiring are OK, suspect a faulty glow plug controller.
Potential Causes:Glow Plug Controller
Glow Plugs
Tech Tips:The Wait to Start light and glow plug on time is determined by the resistance of the glow plugs. There is no coolant temperature sensor on this model, so if the glow plugs are the incorrect resistance, the on time will be incorrect.

Customer: replied 7 years ago.

Where is the glow plug controller located at? The relay for the glow plugs on top of the engine only has power to it where the main cable connects. Should I have power to any of the terminals when I turn the key on?


Expert:  Ford expert replied 7 years ago.

the controller is actually what looks like a relay on top

yes there should be power on the big wire feeding the relay

Customer: replied 7 years ago.
I replaced the relay with a new one and it does the same thing. This all of a sudden happened after the truck was sitting for awhile. I only you it to pull a fifth wheel. All new glow plugs on the right bank.As I was saying sometimes when I play with the key the glow plug light barely lights up or other times it flashes rapidly. Could there be something causing this in the steering column. How does the sytem work when you turn the ignition on?
Expert:  Ford expert replied 7 years ago.
what is the resistance of each glow plug , it uses the resistance to calculate the on time
Customer: replied 7 years ago.
I replaced the glow plugs and harness on the right bank. I have noticed that this is one cold blooded SOB. When the temperature drops below almost 70 its hard to start and when it does it smokes. I guess what im trying to say could the left bank harness and plugs do this?
Expert:  Ford expert replied 7 years ago.
yes everything you are saying is indicating that
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