ZD21 Temperature Sensing Question

[atomichead]

Just picked up a ZD21 with 1150 hours and am trying to get acquainted with its systems. There look to be 2 water temp sensors, one by the thermostat (Red/Yellow wire) and one at the back of the head (Yellow/Blue wire). The YL looks to supply the temp gauge while, at least according to the wiring schematic, the RY is attached to a relay. Is this an engine kill switch?

 

[Captain13]

One is the temperature sender that goes to the gauge. I beleive the one with the relay is a thermo switch. In an overheat condition, it activates the horn until the engine cools down. There is also one for the oil pressure.

 

[PoTreeBoy]

On the L35, that sensor tells the glow plug timer to heat longer when cold, shorter when engine is warm. Don't know about your ZD21.

 

[whitetiger]

One is the temperature sender that goes to the gauge. I beleive the one with the relay is a thermo switch. In an overheat condition, it activates the horn until the engine cools down. There is also one for the oil pressure.

That is correct, you and your neighbors defiantly know when one gets too hot.

 

[atomichead]

So oil pressure is just the one sensor that illuminates the idiot light and sounds the horn?

 

[PoTreeBoy]

So oil pressure is just the one sensor that illuminates the idiot light and sounds the horn?

Can you post the wiring diagram?

 

[atomichead]

I've written in my guesses and they don't include a horn

 

[PoTreeBoy]

I've written in my guesses and they don't include a horn

Bottom right corner - that BZ would denote a buzzer. It's switched on when the temp sensor switch closes. You may be thrown off because the switch and relay control the ground side, as opposed to the hot side.

 

[Captain13]

On the L35, that sensor tells the glow plug timer to heat longer when cold, shorter when engine is warm. Don't know about your ZD21.

On my ZD21 it doesn’t seem to regulate the time needed for the glow plugs. Could be but when I turn the key to active the glow plugs, they stay on until crank the engine or release the key.

 

[lugbolt]

the one on the thermostat runs the horn. Remove the connector and jumper the two connections with a piece of wire inside the plug....the horn should work.

the single wire runs the gauge. Pull the wire off, then put the end of it against the bare cylinder head (or any other ground). The gauge should go to full hot.

oil pressure is down low on the block. Same deal pull the wire off and ground it. The light should come on.

 

[atomichead]

Thanks guys. That's exactly what I was looking for