I have a 1983 f 250 6.9 I just picked up it would start just fine with a shot of ether so since the wait to start light never came on I knew something wasn't right so I put new glow plugs and new relay the wait to start light still dose not come on, but now I can bypass the relay and cont to 5 and she fires right up but why dose the wait to start light not come on,when I bypass the relay the light comes on so I know the light works what am I missing

 

There is a controller that reads off of the coolant temp to determine whether or not glow plug use is required. You may still be able to get a new on from Ford, but they are a little spendy. Last I checked on one for a GM 5.7L diesel (pretty much the same as what your Ford uses) they were about $250.

 

where is that located at and how do I check it

 

Usually on the back of the engine, drivers side. It may be threaded into a cylinder head, might be plastic, bout an inch in diameter.

 

Any updates?

 

What's the good word?

 

Thread starter can reopen if he/she desires, as we can assume the problem has been fixed.