L2850 Glow Plug Operation

[Springmeadows]

I have a 1988 L2850DT with five terminal key switch. Wiring schematic shows terminals G1 and G2 going to glow plugs but key connection diagram shows only G1 connecting during pre heat. Can anyone advise what G2 terminal is for.
Also wiring diagram does not show glow plug indicator which is fitted to dash can anyone advise how this is wired into system.

 

[Dave_eng]

I have a 1988 L2850DT with five terminal key switch. Wiring schematic shows terminals G1 and G2 going to glow plugs but key connection diagram shows only G1 connecting during pre heat. Can anyone advise what G2 terminal is for.
Also wiring diagram does not show glow plug indicator which is fitted to dash can anyone advise how this is wired into system.

I have not looked at the wiring diagram for your tractor so my answer will be a bit generic.

If you have a glow indicator on your dash, a small wire which glows as you heat the glow plugs, then my answer goes like this.

During pre-heat stage, the power to the glow plugs flows through the glow indicator which is wired in series with the glow plugs.

During the engine cranking phase, the glow indicator is bypassed but power continues to flow to the glow plugs.

If you check I think you will find G2 is powered during engine cranking and is bypassing the glow indicator

Dave

 

[Roadworthy]

I concur completely with Dave's response but will expand slightly. The glow indicator is actually a voltage dropping resistor. It drops the tractor's twelve volts to the 10.5 volts the glow plugs use. During cranking by bypassing the resistor the glow plugs get the full twelve volts for additional heat.

 

[Springmeadows]

I have not looked at the wiring diagram for your tractor so my answer will be a bit generic.

If you have a glow indicator on your dash, a small wire which glows as you heat the glow plugs, then my answer goes like this.

During pre-heat stage, the power to the glow plugs flows through the glow indicator which is wired in series with the glow plugs.

During the engine cranking phase, the glow indicator is bypassed but power continues to flow to the glow plugs.

If you check I think you will find G2 is powered during engine cranking and is bypassing the glow indicator

Dave

Hi Dave,
Thank you for your prompt and very helpful response.
Denis

 

[Springmeadows]

I concur completely with Dave's response but will expand slightly. The glow indicator is actually a voltage dropping resistor. It drops the tractor's twelve volts to the 10.5 volts the glow plugs use. During cranking by bypassing the resistor the glow plugs get the full twelve volts for additional heat.

Hi Roadworthy,
Thanks for your contribution.
Good to know that running glow plugs at full system voltage for short period during cranking is acceptable.
Denis

 

[Strodad]

Did you get your problem fixed? I just picked up a 1990 L2859. I think I have an issue with my key switch and my glow indicator does not light when I turn the key counter clockwise.

 

[RCW]

Did you get your problem fixed? I just picked up a 1990 L2859. I think I have an issue with my key switch and my glow indicator does not light when I turn the key counter clockwise.

Springmeadows was last on OTT shortly after that last post November 2020.

If you click on their name thingy (avatar ?), their history should come up.

 

[Russell King]

You should NOT expect to see that indicator glow if it is the style described as a hole in the dash that looks like a cigarette would fit in with a curved wire down behind the hole.

If it was brand new, glow plugs brand new, a bit dark and you held it on glow for a good while you could say it glowed. Otherwise it is a dim thing that you might notice in the dark of night when starting the tractor,