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I have a 1994 9600 John Deere and the oil pressure light came on. I checked the oil pressure which is fine. I then replace the sending unit and light still doesn’t go off. I then checked the wire going to the sending unit and that has no power. Any ideas?
 

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I would have a look at the connectors on the lower right hand side of the cab first. The lower forward connector of the four is the one containing wire #705 leading to the oil pressure sender. This leads to connector 701 which is located right near the relays beside the batteries. Pin "A" on the oil sender connector (wire #10) should have continuity to ground.

I also sent you a PM
 

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With the key on and engine not started, you should have some voltage (5-12V likely) on wire 705. If not, the wire is broken, or there is a problem in the monitor. Once the engine starts and oil pressure comes up, the sensor shorts that wire to ground. As noted, the ground must be good.
 

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Thank you for the info. I have been working on the "705" wire at the cab junction by the door. It is dead going to the oil sending unit with the key on. But from the power distribution board there is another wire "705a' that runs to the LH Main /Cab connector which test 11.38 volts. On the wiring diagram, it shows that 705 and 705a connect somewhere-do you now where that would be? And do you know if 705 runs into the cab or out? Can't find it anywhere
 

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I'm not sure if I'm understanding you correctly, but are you saying you found 705* at the distribution board and it has ~11 volts?

The schematics in the diagnostic manual don't show the wire number suffixes unfortunately. If you have found a 705A at the LH main/cab connector, then I'm fairly sure that is the only wire involved. There won't be a straight 705 there.

The sender is actually powered from the distribution board from relay K3. I've attached the relevant schematic. Ignition switch feeds K3's coil and the sender completes the ground path to activate the relay. Depending on specifically where you measured the 11 volts, you might want to replace relay K3 as it may have an open coil.
 

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Discussion Starter #7
thank you for your all your help I have a service book it is hard to understand where the wires run. by the cab door wire 705a with the combine running shows 13 volts. 705a looks like it runs from the power distribution board to the L.h. main /cab connector I grounded that 705a with engine running light went out also my header would lift. but the 705 wire that looks like runs under the cab to the oil sending unit only has 5 volts with engine running. do you know where 705 under the cab ends up to?
 

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The diagram seems to show a junction in the 705 wires somewhere in the harness between the LH main/cab connector and the connector #701 which should be near the batteries. I attached a page showing 701.

Can you find 705 at the LH main/cab connector? And it has 5 volts?

Can you find 705A at the cab connector? It looks like only one of these should actually be at the LH main/cab connector.

If you have 5volts at the cab side of the LH cab/main connector, that would make sense as the warning system is probably using 5 volts as a signal and is waiting for the oil sender to ground it.

You should have 12 volts on 705* at the power distribution board that is coming from relay K3 waiting for the oil sender to also ground that to activate header lift and such.

These two wires must be connected together somewhere in the LH main harness and then continue on to the back of the machine to connector 701 near the batteries, and then finally to the oil sender connector. See if you can find this connector and check for voltage there.

I would check for a junction point for the 705 wires in the harness by the access door in the grain tank or right close to the LH cab/main connector plug.
 

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That one shut down our combine for an afternoon when we first got our 9500. I replaced the connectors with 2 new ones and new ends on the wires and taped it up to keep the dust out. It's never given trouble again. Seems like an excessive solution to a broken wire, but if one breaks the others were installed at the same time.
 
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