I replaced all the glow plugs and control unit on my '93 F350, and it started right up. Several days later, the Wait to Start message would not come on. The positive terminal on the 2nd battery was a little loose, so I cleaned it up and tightened it, and the warning light came on, and it started fine. Now several days later, the warning does not come on, but it starts OK---not instantly, but OK, even in cold weather. I'm not sure if the starting is due to a fundamentally-good engine (very low miles) or if the glow plugs work, but the warning light doesn't. I just removed the air cleaner to check the connections, turned the key, and the control unit started ticking like a grandfather clock! What seems to be my problem ??

 

it will click for a bit after it glows the plugs.it's called afterglow and helps the cold engine run smoother.it's normal.
if it just clicks at first (if it hasn't glowed the plugs yet) then probably some plugs have failed.
you can test the whole thing and fix your indicator light here;
https://www.ford-trucks.com/forums/1...-tutorial.html


motorcraft (made by Beru in Germany) plugs only.
(if someone says otherwise,they're just wrong lol!)

 

Thanks for the tips. When spring returns (50 degrees +) I'll dive under the hood. FWIW, the new GPs are after-market, so perhaps I'll just buy all new Motorcrafts.

 

There should be a purple wire with a Weather Pak connection to turn the light on. It may be disconnected. My truck's voltmeter bounces from 8 ~ 12 volts about 2 seconds after the light goes out. As you stated, it will function OK without the light. I used Bosch glow plugs when I replaced mine 10~12 years ago.

 

I checked all new GPs and found them to be working per recommended tests. Also checked all other components for good connections, etc. Took forever, but found how to remove dash cover and WTS panel. At parts store they did not have small bulb, but counter man described how to use digital multi-meter to check for continuity of circuit boards and bulbs in sockets. Found two bulbs without continuity, removed and reinstalled them, and new contacts made the necessary repair. After reassembly, WTS light glowed, and truck started as expected. I have new appreciation for refreshing contact points.