G1800 Electrical Problem

[EquipmentUser]

Well I got my solenoid flutter fixed, it was a bad connection with one of the fuses. I'm now onto another problem, getting the temp guage working. I notice this unit has two temp senders, one in the head at the front of the engine, I traced the wire to this one and it comes from the guage. It is getting 5 volts and there is 12 going into the guage so i'm figuring the guage is bad, I tried grounding the signal wire hoping the guage would peg or atleast move but it done nothing.

Now on to the interesting part of this, it has another temp sender at the rear of the engine on the thermostat housing directly beside the top radiator hose. I checked this wire and i'm getting 12 volts on it so I figure i'll just ground it and see if the guage moves, well the guage didn't move but the horn blew!!!

I didn't even know this thing had a horn, there's no switch for it, its not on the schematic, I couldn't even find it, its a loud horn too, its buried in the back end somewhere. So now i'm dumbfounded, i've never seen anything like this before. The only thing I can figure is this is a "backup" temp warning system, if the engine heats up and the operator ignores the guage the horn goes off and doesn't stop until it cools back down. Its not like somebody has messed with the wiring or anything, you can tell it is factory and not just something that someone has done. This is crazy.

 

[LQPAPPY]

You are correct that the horn is high temp warning alarm. My G1900 has the same feature. My fuel gauge does not always work when the engine is running but seems to work after a good bump and I think the temp gauge is the same, always felt it is a ground issue but have not tried to trace the problem. Bought my G1900 new in 1992 and it has about 3000 + hours.

 

[jinman]

G1800s above serial number 11582 have the additional warning horn for coolant temperature. That's a backup alarm in case the radiator screen becomes clogged and you don't notice the temperature gage going up.

 

[mjw357]

G1800s above serial number 11582 have the additional warning horn for coolant temperature. That's a backup alarm in case the radiator screen becomes clogged and you don't notice the temperature gage going up.

Or not notice the guage not going up.

Regarding the fuel solenoid, I was working on a power yacht that had twin diesels one time. I noticed they had placed big diodes in the wiring to prevent chatter like the OP is experiencing. Some poking around online should yield some applications that would show how this is done.

 

[jinman]

Or not notice the guage not going up.

Regarding the fuel solenoid, I was working on a power yacht that had twin diesels one time. I noticed they had placed big diodes in the wiring to prevent chatter like the OP is experiencing. Some poking around online should yield some applications that would show how this is done.

Normally diodes are added in reverse for normal operation in an inductive circuit and keep relays, switches, and solenoids from bouncing when they are de-energized only. The diodes have no function when the device is first energized. The diode shunts the current induced by the collapsing magnetic field around the devices coil when de-energized.