New Holland 1720 will not start

[toddt]

have you bypassed the NSS?

Both the Transmission and PTO NSS switches are good. The PTO switch is a bear to get to.

The glow plug timer relay part number on tractor is SBA385870300 the one that was just purchased is different by one digit: SBA385870301 the parts guy said it was improved version?? Wonder if that makes a difference?

 

[Soundguy]

a relay is basically a switch to actuate large current with small current. if it meets the specs.. I doubt it's a problem. ( IF ).

you see PLENTY of superceeded parts on older machines.

have you checked to see if the new relay IS energizing as it shoud?

 

[jimmysisson]

I thought I read on here the timer was just for the light, and current to the GPs was controlled by the ign switch. (Maybe that's only on a newer model.) Do you get current to GP bus bar full as long as you hold switch in Heat position?
Probably you need someone better informed than I.
Jim

 

[toddt]

\have you checked to see if the new relay IS energizing as it shoud?

Have been looking for a diagram of the Timer Relay but have not been able to find one. It is not a real relay therefor I'm unsure of how it works without seeing the diagram (circuit with pin numbers). It is my understanding that it controls how long the voltage is applied to the glow plugs. It is an "NGK lamptimer 12vdc". From all that I have read it appears that most diesels have a timer like this. I'm about to give up and have it trailered into the dealer however, the closest one is 40 miles away and I can still jump from the battery to the glow plugs to get her running. I'll probably keep fooling with it until something lights the dim bulb in my head.

 

[Soundguy]

a test lamp should tell you what pin is going hot (timed) when it is on.. etc.

 

[toddt]

a test lamp should tell you what pin is going hot (timed) when it is on.. etc.

Success, thanks Soundguy for sticking with me on this problem. Got out my test light and started tracing wires and voltage. Got back to the ignition switch had the voltage on the ignition switch but not at the plug that was 8 inches from the switch. Stripped away the heat shrink and there it was a broken wire. It has been repaired and the tractor is happy.

 

[Soundguy]

don't you love the easter eggs. IE... hidden problems you have to find.

glad you found it!

 

[toddt]

don't you love the easter eggs. IE... hidden problems you have to find.

glad you found it!

I remember "easter egging" from my navy days...

 

[jimmysisson]

Was the "plug" a wire connector in the glow plug circuit? Did you determine the relay times the GPs, not just the light?
Glad you got her fixed.
Jim

 

[toddt]

Was the "plug" a wire connector in the glow plug circuit? Did you determine the relay times the GPs, not just the light?
Glad you got her fixed.
Jim

Jimmy, the plug is right off of the ignition switch. It has all the wires from the ignition switch going into it and the broken wire was hidden under heat shrink tubing. I had removed the ignition switch and checked continuity right between the posts on the switch. No, did not determine the relay times, I am assuming that it is the same time that the GP light is lit.