MF glow plug voltage

[arizona98tj]

PS-- and yes, if that indicator glow plug is in series with the rest (as it should be) and it's flaky, that will also create the symptoms. You might try bypassing that to see if the others get hot.

The indicator glow plug is in series with battery, switch, and the other glow plugs. As such, it will cause a voltage drop across itself. This means that by design, the other glow plugs will NOT see the full 12 volts from the battery. This would imply that the other glow plugs are NOT fully rated for 12 volts....OR.....for whatever reason, the engineering folks did not want to apply 12V to the glow plugs.

Anyway, something to think about before you decide to hook 12 volts to the other glow plugs. I can't speak as to why they designed the circuit that way......only the results of what happens when the switch is closed.

 

[PILOON]

The glow plugs are in a parallel circuit and I believe the indicator also is. eg acting like another glow plug.

The easiest test of all is the fact that the plugs will be hot! Simply touching each one will confirm operation.
Voltage will probably be about 9-10 VDC when on as the draw is sufficient to cause a drop in voltage.
Ultimate test is to run a jumper direct from battery + to the plugs and check for warmth.

 

[arizona98tj]

My comments were based on the diagram that was shown. If that wiring diagram is correct, then the indicator is in series with the other glow plugs, not in parallel. The 3 glow plugs are in parallel with each other, but not with the indicator. If that diagram is not correct, then it should be removed since it is providing incorrect information.