No overheat (or any) alarm, VRO was removed, Stray tan wire?

waynehol

Petty Officer 3rd Class
Joined
Jun 4, 2009
Messages
88
Hi all,
I have a 1988 Johnson 90hp. The VRO was removed before I bought it. The alarm horn doesnt work at all. I tried to test but no go so I am replacing the wire.

On the engine there is a tan wire coming from the overheat sensor on each (of 2) heads. The wires connect together and to a third "tail" at a point before the harness connector. The "tail" is not connected to anything.
By the way, the tan wires agree with the wiring diagram from my manual.

Q1) Did this wire go to the VRO? Can I cut it?

The tan wire then goes into the harness connector and on up to the helm where it connects to the horn (again, in agreement with the wiring diagram) There is also a purple wire connected to the horn and I cant figure out what that is.

Q2) Could the purple wire have been for the low oil level alarm on the old VRO?

Q3) When I replace the alarm horn, how do I check the temp sending units to be sure they send a signal to the alarm horn? Do I ground them at the head or connect a hot lead to them? (Seems elementary but I am still learning about how o/b wiring systems are different and I get a little confused)

Q4)Final questions. Are these temp sending units pretty reliable? If the test for the circuit works, can I assume the temp sensing mechanism works? What I mean is, do these things fail often due to NOT sensing an overheat and therefore NOT sounding the alarm?

Wow, that seems like a lot of questions. I really appreciate your thoughts on this one. By the way,. I do have a manual for the engine and doing the best I can following it!
 

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

Purple is typically a switched hot (+) lead. Tan is hot horn lead (test by grounding ... horn should turn on. The temp sensors are very reliable.
 

waynehol

Petty Officer 3rd Class
Joined
Jun 4, 2009
Messages
88
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

Ok that makes sense, thanks/
The horn does not work. Do I need OEM part? It's like $72.00. an I use a generic horn?
 

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

I would guess any 12 VDC horn might work, but most are not weather resistant.
 

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,198
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

with ignition on, run a wire from the tan terminal at the horn to the engine ground, if horn doesn't sound its shot.

double check by connecting the horn straight to the battery.

I think a sierra horn is a LOT cheaper than OMC.
 

waynehol

Petty Officer 3rd Class
Joined
Jun 4, 2009
Messages
88
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

I tested the horn as suggested and it is shot. No sound at all.

So yesterday I purchased a marine buzzer/alarm at my local marine supply store and will try that. It is made for marine applications and will be installed underneath the console.

My only question now is that there are 3 wires to my current horn. One tan (from the overheat sensors) One purple (that runs to the control box. I think this is the hot wire that is only hot when the ignitiion is on) and another I think White wire. Where would that one go? My new buzzer only has 2 terminals

Thanks guys
 
Joined
Dec 17, 2002
Messages
29
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

check the manual but I would say it's the vro low oil wire.
 

waynehol

Petty Officer 3rd Class
Joined
Jun 4, 2009
Messages
88
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

check the manual but I would say it's the vro low oil wire.

Yep that has to be it. The VRO was removed so I dont have to worry about that one. Thanks!
 

wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

Wayne, check your PM's.
 

jonesg

Admiral
Joined
Feb 22, 2008
Messages
7,198
Re: No overheat (or any) alarm, VRO was removed, Stray tan wire?

single grey wire is all the alarms. they are isolated from each other by diodes.
 
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