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Overheat alarm sounds constantly.

G

gkm24

Regular Contributor
Even with the Tan wire disconnected to the sensor on the head of my Johnson 70 VRO 1992, the alarm still sounds. If I disconnect the VRO 4 pin plug the sound goes quieter and if I disconnect the oil tank 2 wires it stops. If I then connect the sensor on the head, the alarm does not sound. I have checked all wires and voltages inc grey wire to terminal board tach wire, black to good earth, purple to switched live, tan to engine temp circuit. I also checked the oil tank level sensor.
Only thing that has changed is a tacho has been fitted which is my next point of testing. I have not tested what I assume is a diode on the temp tan circuit wire.
Any help really appreciated.
 
Sounds like the the 2 wires to the tank are shorted.

A low tank level would be a sound every minute or so.(if the motor is running)

Does your tach work?

Disconnect the the two wires to the tank and short each head's temp sensor's tan wire - horn should sound

The horn will sounds for (all tan wires)
No-Oil - comes from VRO
Low -oil - comes from oil tank
High temp - comes from head sensor
fuel restriction - comes from vacuum switch, which I believe this motor doesn't have that feature


I had to run all new 2-wire cable from the connector in the engine cowling to my tank as I wasn't getting the low-oil warning....I was lucky, I had JUST enough oil in the tank when I got home....whew
 
Thanks for your reply. The tacho does NOT work so I will have to source another.
The two wires to the tank have been tested and are not showing any high resistance or breaks in the sheath. I guess it could be the electrics on the VRO but I know the engine is getting oil due to the smoke and I used it all last season with no problems and the oil level was reducing every day in the tank.
 
???-----The stator / tachometer signal sends pulses to the " no oil " warning circuit on the VRO.------It may be telling the system that VRO has failed.-----The VRO can still be working properly !
 
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