Have a 1986 F350 6.9L diesel - glow plug circuit is not working. I've got 12v to the controller - but no voltage from controller to the relay.

All signs lead me to believe the controller is bad - but seeing as these things are $75 (or more depending on where I get it) i'd like to be 100% sure before replacing it.

Any way to test the glow plug controller - or perhaps even repair it?

Any info or advice greatly appreciated. Thanks!

 

Get a Haynes diesel book, the test procedure for the early style controller is about 6 pages long.

When mine died they were 150 dollars for the controller.

I wanted to make sure it was the controller, so I started through the test proceedure.

I made it to about the third page before I said forget this and converted mine to manual control.
That was probably 9 years ago.

I now have a late style harness and glow plugs.
The relay and controller is laying in the garage, it has been there for three years.
Brand new, still in the box, never installed, and probably never will be.

 

Yeah - right after I posted I started seeing the info about installing a manual control switch. It seems like the best thing to do - one less point of failure in the circuit and $150 more in my pocket from the controller i'm not going to buy.

I'll give it a try this weekend, thanks!

 

The only downside to manual control is if other people drive the truck.
They can't seem to get counting seconds to hold the switch ON.

But then count downs are part of rocket science aren't they.

 

How long (seconds) should the glow plugs be heated before cranking a cold engine?

 

I do 10 seconds on mine.

If the temp is below zero I add 2 or 3 seconds more.