L275 GLOW PLUG RELAY

[Matt...]

Hi all,
My L275 starts 3 crank when the glow plugs operate. (ie when the glow light turns on) but its extremely intermittent. Some times i note it on while its running 20 mins later.
According to the wiring diagram, only the ignition switch will turn them on? Is there any other switch - say like a thermistor that will activate the plug if it is cold?
Was thinking about wiring a push button directly to engauge the plugs and insuring that they dont operate for for periods of time while the engine is running.

 

[Pawnee]

I think you need to replace the starter switch. The plugs should be off when the engine is running and the switch controls that.

 

[Dave_eng]

I marked up a L275 wiring diagram to explain how the GP's are powered depending upon the key switch position.

The blue circuit path flows through the GP indicator which is really just a resistor to limit the voltage the GP's experience. Key switch terminal G1 is the path through the resistor.

The yellow circuit path to the GP's bypasses the GP indicator/resistor. This happens because the draw of the starter lowers the voltage the GP's see to about the same level as when the resistor is in the circuit.

In summary, the GP's are powered during the preheat stage and also when the engine is cranking.

Pawnee is correct is suspecting the key switch.

I would further suggest you examine the back of the switch to see if terminals like G1 and G2 are present.

It has happened that someone replaces a key switch with a generic one and defeats the intended design..

There is no good reason to start modifying the wiring with a unique switch

Dave

 

[Russell King]

Does the L275 you have have a key switch and a starter switch (like my L185)?

I don’t see any indication of that on the schematic and it is not really going to change anything much really.

I recommend you see how much the glow plugs and the indicator and the starter switches cost from the dealer. For my L185 the two switches were $30 each, indicator was $25 and glow plugs less than $10 each.

Replace and wire correctly and clean up any corrosion and hacked wiring. It is truly a very simple system and easy to repair.