wierd glow plug controller
 

Turn key on and no glow plug light then it turns on next time no glow plugs at all.

I checked the controller red wire has power with key on, when i jump the brown wire to ground and turn the key on it works, so i check the repair manual and the brown wire is engine temperature sensor.

I find two temp sensors, one is the gauge the other is the heater interlock.

Where is the temp sensor for the glow plugs?

I tried grounding the temp sensor circuit on both sensors and the temp gauge responds as expected and the other one does nothing but allow the heat to work on a cold engine but still no glow plug controller engagement.

I jumped the brown wire as a temporary fix for now but would like to replace the temp sensor if i can figure which one it is.

Anyone know?

Oh it is a 84 300sd 617 motor.
Steve

the one that when grounded jumps the temp guage is the one for the guage.. correct

the other... on the same side has a wire.. follow the wire .. it should lead into the glowplug harness.. I know mine does.. unless its an 85 only deal... which could be true

More details please.

This description of symptoms is woefully inadequate to assist in a diagnosis.........much less a solution.

The glow plug controller worked intermittently then stopped all together.

I checked all connections at the controller and cleaned them.

fiddling with the wires produce no results.

Red wire on the controller has power with key on.

controller works when i ground the brown wire/terminal at the controller.

book says brown wire is engine temp sensor.

I grounded both temp sensor wires at the sensor and glow conntroller no work.

That is all i have done so far other than jumping the brown wire to ground for temporary operation.


I also tried two other controllers with the same results.

I only have one temp sensor on the driver side and one on the termostat housing.

does one sensor have dual service?

I have grounded both and still no controller operation, it only works when i ground it at the controller itself.

Maybe a break in the wire?

Steve

The FSM shows the brown wire as a typical ground wire. There is no external temperature sensor..........it's internal to the controller.

As a typical clue..........M/B always uses brown as the ground.

hey thanks Brian, I guess i am ok as is then being that i ran it to a ground.

I must have a break in the wire harness somewhere.

Steve

There have been threads on here in the past which referred to a temperature sensor in the head which tied into the glow plugs. Are you saying there is no such thing? I remember one thread in particular where it was discussed in relation to a conversion from series to parallel plugs.

I can only comment on the '81-'85 SD for which I have schematics. On those vehicles, there is no temperature sensor in the head.

Am I over-simplifying if I ask if you have checked the condition of the glow plugs? More than 1 or 2 inop will cause light not to come on. Right??

Right.

Jimmyl

You are right but when i ground the brown wire at the controller it operates as normal also car starts and runs on all five cylinders.

My experience has been, if a glow plug or two is out it will not fire on that cylinder for a moment or two if it will start at all depending on the temperature.

Yes Brian you are correct, my car has no temp controller for the glow plugs.

It is a faulty ground, the brown colored wire should have tipped me off.

Thanks all

Steve

Hey Brian-

I just looked at the wire diagram again and the wire i thought was for the temp sensor IS the temp sensor in the controller not a wire to the sensor:idea3:.

Duh :oon my part.

Steve

The temp sensor is in the controller and the brown wire provides the ground for it. AFAIK, it just varies the time that the glow light remains illuminated. I haven't seen any change in times for the plugs themselves.