low coolant sensor/roadmaster chassis parts

[bcrow8778]

I have a 2000 monaco diplomat on a roadmaster chassis. The low coolant light stays on. I need help. Where can I find parts for a roadmaster chassis.

[InfinityJim]

A lot of the Monaco’s have the low coolant sensor in the expansion tank. You might have to unbolt the tank in order to remove the sensor, clean it with scotchbrite and soap & water before re-installing. The sensor is about 8 inches long and about 1/2” round diameter aluminum, with a single wire hooked up to it. They get a build up on them that messes up the continuity, or the coolant is over concentrated.

[bcrow8778]

Where can I get a wiring schematic for a 2000 monaco diplomat. I talked to a service rep. at monaco and explained my low coolant light being on. He said to ground the wire out that goes to the sensor and if the light did not go out it was a bad wire somewhere. I grounded the sensor and the light still stays on.

[Mike Canter]

Now I am totally confused. What ground wire? You stated that there was only one wire that went to the sensor. Did you mean one pair or one wire? There has to be current flow between two probes for this sensor to work. So there has to be two wires going to it. If you really truly want to know if it is the sensor or not is to disconnect the plug from the sensor and jump across the two pins in the plug. If the light goes out then sensor is either corroded and needs cleaning or it is bad. If the light stays on it is some other problem in the MH.

[bcrow8778]

There is only one wire going to the sensor. The tech said to take that wire off and put it to ground. He said if the light goes out it is the sensor. If the light does not go out it is a wiring issue.

[Mike Canter]

Like I said there has to be current flow through the sensor and that is what the tech guy is telling you by jumping that single wire to ground. SO the big question here is how does the ground get through the coolant to the sensor and this can also be the problem. There has to be fairly short ground path through the coolant to the sensor meaning there has to be a ground probe or something and that could also be the problem. But I would do what the tech says first by shorting that wire to ground. If the light goes off then I would pull the sensor and scotchbrite it clean. If that doesn't fix it then you need to find the ground path through the coolant and see if that is connected tight and clean.

[InfinityJim]

On a single wire hook up, the circuit is completed to ground thru the water in the coolant thru whatever metal it touches in the system grounded to the frame which in turn the battery is also grounded to frame, completing the circuit. Now if the coolant is not mixed right, say 60/40 instead of 50/50 then that might be enough resistance to not allow the circuit to be completed. In that case drain some off and add water, of course it that's what your speculating it's best to send a sample off to the lab (such as fleetguards) and they'll tell you exactly what the coolant needs which in turn will probably fix that problem and more importantly bring the coolant back to specs and save your cooling system.