2 temperature senders?

[Toyman]

As I wait for my new head gasket (M4050) and other parts to arrive from Messicks, I started buzzing out some of the wiring. On top of the head, there is a sending unit and on the left side of the block, near the starter there is another sending unit. From the parts diagram on Messicks the sender on the head should be the temperature sender. I cannot find the sender on the block in the parts diagrams. The odd thing is when I buzz out the wires, there is resistance to the 'U' terminal on the temp gauge from both senders? I haven't run it long enough to see that the gauge works as I had bigger fish to fry, but very confusing. I also tested the wires back to the oil idiot light and there was no continuity from either of the sender wires. Any help is appreciated!

 

[PoTreeBoy]

As I wait for my new head gasket (M4050) and other parts to arrive from Messicks, I started buzzing out some of the wiring. On top of the head, there is a sending unit and on the left side of the block, near the starter there is another sending unit. From the parts diagram on Messicks the sender on the head should be the temperature sender. I cannot find the sender on the block in the parts diagrams. The odd thing is when I buzz out the wires, there is resistance to the 'U' terminal on the temp gauge from both senders? I haven't run it long enough to see that the gauge works as I had bigger fish to fry, but very confusing. I also tested the wires back to the oil idiot light and there was no continuity from either of the sender wires. Any help is appreciated!

I don't know about the M4050, but the L35 has 2 temp. senders. One works the gauge and the other works with the glow plug timer to make the plugs heat longer when it's colder.

 

[Dave_eng]

I do not think the M4050 made between 82 and 85 is going to be very sophisticated as far a glow timer etc.

If the sensor on the side of the block has more than one wire, it may do two functions..... move the needle on a oil pressure gauge and turn on an idiot light. Like a fuel gauge which may also turn on an idiot light when the fuel level is low.

Oil pressure sensors/switches usually have some physical proximity to the oil filter as far as a internal oil gallery in the block.

I cannot find any manuals for a M4050. The next series is M4500 but its info only shows a one wire oil pressure switch connected to an idiot light.

I cannot speak about the instruments on a M4050 but some old tractors utilized a mechanical voltage regulator for the instruments. This regulator helped stabilize the instruments as the voltage was not fluctuating but also provided puzzling current paths when troubleshooting.

If there are more than one wire on this block sensor, please provide the wire colors.

Dave

 

[whitetiger]

Here are a couple of pdf's

 

[GeoHorn]

The one on the block sounds as if it’s the oil pressure sending unit.

 

[North Idaho Wolfman]

Only one temp sensor the other by the starter is oil pressure.

 

[Toyman]

Both are single wire. The one on the block is blue and the head is red?with black stripe. There is an oil idiot light that turns on with the key and goes out once the tractor starts/oil pressure comes up. The light works as it should, but doesn’t show continuity to the blue wire. It does however show continuity to the temp gauge. Thanks

 

[ruger1980]

Both are single wire. The one on the block is blue and the head is red?with black stripe. There is an oil idiot light that turns on with the key and goes out once the tractor starts/oil pressure comes up. The light works as it should, but doesn’t show continuity to the blue wire. It does however show continuity to the temp gauge. Thanks

Are disconnecting the wires when checking continuity? You should isolate a circuit when doing so.

 

[ruger1980]

Also the simplest test is to disconnect the wire to the sensor or switch check the condition of the gauge or light then ground the wire and check condition again.

 

[Toyman]

Yes, wires are currently disconnected and that is how I tested back to the temp gauge. I'm in the middle of replacing the head gasket and figured Id buzz out the wires while I have a bit more room, but obviously battery is out and hot testing is out for now. None of this part of the wiring seems to be hacked up. I had a lot easier time buzzing out my entire wiring harness in my 70 Chevelle than the 5 circuits in this tractor Thanks for the help.