Glow plug light comes on then off - 1992 Ford F250

Glow plug relay, or it's fuse?

With most relays, you have 4 wires. One is power to the component the relay controls, one is a ground to the relay magnet, one is power to the magnet, and the fourth goes to the component, in this case the glow plugs. The ground usually comes from the computer.
With the key on you should have power to two terminals and you would jumper the hot terminal to the glow plug terminal. Or use a test light or meter to check for power on the glow plug circuit.

Your diesel vehicle is equipped with glow plugs, and also with a Glow Plug Light that will either come on and stay on, or flash or blink when a fault is detected by the ECU (engine management unit). When the Glow Plug Light comes on, the ECU stores information about the condition that has caused it to come on.4 Jan 2016

Is It Safe to Drive With the Glow Plug Light On? ' YourMechanic Advice

https://www.yourmechanic.com/article/is-it-safe-to-drive-with-the-glow-plug-light-on Glow plug light wont go out Google Search

the glow plugs work through a relay so check the relay and wiring for the relay from the ignition switch

GLOW PLUG LIGHT BULB IS BLOWN.IF BULB IS GOOD BUT GLOW PLUG LAMP FAILS TO LIGHT PROBLEM COULD BE ECM OR GLOW PLUG RELAY.

most time when glow plug light come on your glow plugs not working.check fuse if fuse is good problem is in glow plug relay.

Glow plug fuse under hood of car, driver side close to head light . There is a cover pull off and see the blown fuse.

Ask a friend and not a computer.

Does the glow light come on? Check for power with a test light on the glow plugs.

glow plug relay is going out