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Discussion Starter · #1 ·
My temperature gauge light on the digital dash stays on even when started cold. The thermofan switch works fine and the fan comes on when the motor reaches temperature. I original thought it was the sending unit and replaced it. I checked both the new and old sending units with an ohm meter and both sending units are good. When the wire that attaches to the sending unit is grounded the dash light goes out. I have checked all the wires and I'm at my wits end to get this light on the dash turned off. Any help on where else to look would be greatly appreciated.
 

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My temperature gauge light on the digital dash stays on even when started cold. The thermofan switch works fine and the fan comes on when the motor reaches temperature. I original thought it was the sending unit and replaced it. I checked both the new and old sending units with an ohm meter and both sending units are good. When the wire that attaches to the sending unit is grounded the dash light goes out. I have checked all the wires and I'm at my wits end to get this light on the dash turned off. Any help on where else to look would be greatly appreciated.
That is strange...

Are you saying you get good ground from the sender terminal with the ohm meter with the wire disconnected...

And that grounding the wire turns the light off (as it should)....

And that when you put the wire back on the sender it won't shut off...

If that is the case...I think you are either not getting as good a ground through the body of the sender as you think...or the connector is not making solid connection...

I would cut the oem connector off and use the bare wire to verify the system works with a good connection...then crimp a lug on and put a nut(s) on the stud...

Or you can just ground the wire....

I would highly recommend a gauge...

Gaffrig Marine full sweep electric is the best for a rhino imo...
 
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Discussion Starter · #4 ·
I was never a fan of the dummy light. I am going to put a gauge in but I would like to problem solve the issue with the wiring of the sending unit. I am going to have to get the wiring schematic and find out were my problem lies. I cut off the connector and bare wired to the sending unit and the light still stays on. When touch the wire to a bolt on the motor it gets a good ground and turns the light off. I am stumped.
 

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If that is the case...I think you are either not getting as good a ground through the body of the sender as you think...or the connector is not making solid connection...
Ohm out the sendor one more time...

Make certain your meter is on the lowest resistance scale...

Zero the meter by shorting the leads and verify that it reads 0.00 ohms...

Then ohm the terminal (wire disconnected) to the brass body... You should still read 0.00 ohms...

Then ohm the body to the aluminum housing...it should still be 0.00 ohms...

Then ohm terminal to the housing...it should still read 0.00 ohms...

When you find resistance to ground...you have isolated the problem...

It may be a poor connection to ground between the body (threads of sendor) and the housing...

Posssibly due to the thread sealant....

It may be as simple as chasing the hole with a 1/8-28 BSPT tap to clean the threads and cleaning the threads of the sender real well with a brass brush...

It would be in your best interest to solve the problem before installing a new sendor and/or gauge...
 

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Discussion Starter · #6 ·
Thanks everyone for the quick and helpful replies. It seems after all yamaha sold me a bad temperature sending unit. Just finished putting a mechanical gauge and a volt meter in. Thanks again,
Mike
 

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Thanks everyone for the quick and helpful replies. It seems after all yamaha sold me a bad temperature sending unit. Just finished putting a mechanical gauge and a volt meter in. Thanks again,
Mike
I am having pretty much the same issue with my 2006 Rhino 660. The OEM idiot light stays on unless I disconnect from sender ( at thermostat housing) and ground it. I have installed a temperature gauge but I don't like warning lights being on. This tells me that the light must be grounded to turn it off. Disconnecting from ground and the light comes on. I have ordered 3 or 4 thermoswitches, Yamaha Part Number 4BA-82560-00-00. Either this is the wrong part or they are all defective. The book does say that if dropped, it must be replaced. Shouldn't I be able to bench test (OHM meter) from the threads on the sensor to the spade for the wire and have continuity? When overheated, it breaks continuity and the light comes on? If the above part number is not correct, can someone please provide the correct part number? This is what the part schematic shows but they all arrive with an open circuit.
 

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Might be something to check...

Thanks Dave for the reply. I thought I replied about a week ago but apparently it didn't post. I went to the Yamaha dealer yesterday and they have no knowledge about this issue. I printed a few pages from the service manual and took them with me. The manual says that the thermoswitch for the overheat light should be closed below approximately 248f degrees and open over approximately 248f degrees. The manual shows a test that the thermoswitch should have continuity when cool and lose continuity near 248f degrees. I have ordered about 5 thermoswitches and they all arrive with an open circuit at ambient temperature. The dealer couldn't tell me which thermoswitch I needed, 4BA-82560-00-00 or 5KM-82560-00-00. They didn't have either switch in stock. The manual reads that the switch must be handled with care. Do not drop it or it must be replaced. Good luck to me trying to find out what to replace it with and trying to get one that isn't defective when its received.
 

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After ordering 5 temperature sensors for the thermostat housing, the 6th (5KM-82560-00-00) seemed to work. I bench tested it and it tested good. I checked for continuity from the end of the sensor to the connector for the wire and it showed continuity. I installed it and the overheat light is no longer on. The 5 previous sensors showed an open circuit right out of the box. I had been to the local Yamaha dealer and two mechanics could not tell me which part I needed, 5KM-82560-00-00 or 4BA-82560-00-00. Overheat light is off, problem solved.
 
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