L48 alternator/glow plug issue?

[Jason280]

Troubleshooting time.

I checked the battery with everything off, normal 12.7v. After some flashlight and Google searching, found the location of the glow plug controller & relay.

Pulled both, and cranked the tractor....no dash light, and 14v to the battery.

Now, I have to figure out whether it's the relay or controller....except I have no idea how to troubleshoot either.

 

[Dave M7040]

Dave7040,

Is the glow plug current draw constant or does it change as the GP heats up? I was under the impression it would pull 10-12 amps, but that it would drop off as the element heats up due to the resistance increasing. I've looked for graphs of the current over time, but haven't found any.

I'm with you in thinking GP remaining on is not the problem.

moship

There is not a simple answer to your question regarding glow plug current draw over on time.

Designs are continually being improved to shorten warm up time and thus reduce emissions. Some are now designed to stay on after the engine starts to improve combustion and lower emissions until the engine is warm.

In the early days of diesel VW's, to make the engine start up without a pre heat time for the GP's, i.e. to make it operate like a gas engine, VW designers triggered the GP's on as soon as the drivers door handle was touched on the outside of the car. In this way, by the time the driver sat down, the glow plugs were hot.

The article I have attached in a photo describes a newer design which incorporates both a current regulating coil and a heating coil.

Dave M7040

 

[rbargeron]

Had a similar intermittent glow plug light and occasional run-down battery on my L48. If working right, the controller is supposed to ramp glow plug current down automatically with time and temperature, but mine sometimes did not. Plugging in a new controller cured it.