1985 Johnson overtemp. sensor

rbc

Seaman
Joined
Apr 18, 2004
Messages
71
1985 70 HP mod.E70elcos<br /><br />I replaced the overtemp. sensor because the connector tip was bent and when I connected the brown wire to it the steady alarm went off. The new sensor also causes steady alarm. Turn key one step and steady alarm goes, start engine and alarm stays on. Engine has good coolant stream. This is sensor that screws in to bracket at rear of engine and touches the head.<br /><br />rbc
 

angus63

Captain
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May 20, 2002
Messages
3,726
Re: 1985 Johnson overtemp. sensor

Horn sounds when tan wire is grounded. Check to see if the insulation is weak along the wire (burnt,frayed,etc..) and grounding the circuit.
 

rbc

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Apr 18, 2004
Messages
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Re: 1985 Johnson overtemp. sensor

Angus thanks for the reply.<br />I checked tan wire to ground at about 18 MOHMS,definitly not grounded.<br /> The sensor top to ground is about 470 Ohms.<br /> Any other suggestions??<br /><br />rbc
 

clanton

Rear Admiral
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Jul 9, 2001
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Re: 1985 Johnson overtemp. sensor

That sensor is for a temp gauge, NOT the overheat alarm.
 

rbc

Seaman
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Apr 18, 2004
Messages
71
Re: 1985 Johnson overtemp. sensor

If sensor is just for gauge why does steady alarm go when it is connected to tan wire? When i disconnect tan wire alarm stops. Where should tan wire be connected??<br />rbc
 

Solittle

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Apr 28, 2002
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Re: 1985 Johnson overtemp. sensor

The brown wire is for the overheat sensor. Check tiyr ignition sw.
 

rbc

Seaman
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Apr 18, 2004
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71
Re: 1985 Johnson overtemp. sensor

Motor is new to me and I do not have a manual yet. What does overheat sensor look like and where is it located?<br /> Not sure what you mean by ckeck tiyr ignition sw.<br /><br />thanks<br />rbc
 

clanton

Rear Admiral
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Messages
4,876
Re: 1985 Johnson overtemp. sensor

The temp sensor for overheat in under the water cover on the cylinder head close to the thermostat. The sensors are not the same.
 

xcharged

Cadet
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Sep 28, 2003
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Re: 1985 Johnson overtemp. sensor

i had a similar problem...my overheating horn cut on and stayed on...even after sitting for a week.<br /><br />I ended up having to replace the horn itself.<br /><br />been okay since :)
 
D

DJ

Guest
Re: 1985 Johnson overtemp. sensor

rbc,<br /><br />Look for a tan wire coming OUT of the head. That is the overheat sensor.<br /><br />The guage sensor won't work with the buzzer.<br /><br />kinda cool that you have one though.
 

Joe Reeves

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Feb 24, 2002
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13,262
Re: 1985 Johnson overtemp. sensor

RBC.... I suggest that you obtain a proper service manual before you attempt to do any work on the engine to avoid any expensive mistakes, However.......<br /><br />The "L" shaped bracket that is attached to the cylinder head and has a long brass heat sensor screwed into it is an accessory item. It is not a item that is equiped with the engine.<br /><br />As such, any wiring that would be connected to it would be seperate from the engine harness wiring.<br /><br />That item is a sensor that operates a water temperature gauge. If you have such a gauge, there should be a tan wire attached to the gauge at a terminal marked "S" (usually "S"). Someone may have changed the wire to another color but at any rate, trace that wire back to the engine area. That is the wire that should be connected to that long brass heat sensor.<br /><br />There are other tan wires on your engine that are part of the instrument/engine harness assembly which are necessary to operate the "VRO" and "Overheat" horn warning alarm.<br /><br />You are mistakenly connecting the engine harness tan wire to the wrong sensor, grounding the warning horn circuit which results in having the horn sound.<br /><br />Look at the cylinder head, near the upper portion of the head. You will see a "tan" wire protruding from the head there. That wire is connected to the overheat sensor that is inserted into and as such is part of the cylinder head. This item is what you want to conect that engine harness "tan" wire to, which if connected properly will cause the warning horn to sound off should the engine overheat.<br /><br />At the back of the VRO pump, there should be either 3 or 4 wires leading to a rubber plug type connector. One of those wires should be "tan" also which would be the circuit for the VRO pump warning system.<br /><br />Now, if the VRO pump exists, should it fail, the warning horn would sound every other second. If the engine overheats, the horn would sound steady and constantly.
 

rbc

Seaman
Joined
Apr 18, 2004
Messages
71
Re: 1985 Johnson overtemp. sensor

Joe and the rest.<br />thanks to your help I have it figured out and all is ok.<br /> Once I had it fixed took boat for ride and got another lesson. I wanted to run out the 12 gal. tank in back of boat and then hook to forward 6 gallon. Well engine finally sputtered and died so I conected up to tank but wasn't figuring on 12 foot hose taking so long to pump back full, Ended up testing 3.3 Merc. kicker which ran fine but bracket is made for 115 lb. motor and consequently won't go down all the way. Anyway got back to dock with some more things on my list. I think I want to get rid of Merc. and bracket and just bolt on a long shaft something. Any suggestions?<br /><br />thanks<br />rbc
 
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