low coolant light stays on

[Jim McGarvie]

Our low coolant light remains on regardless of coolant level. Is there some way of testing the sensor and/or the rest of the circuit? It is a one-wire sensor mounted low on the side. I cut a couple inches off the end of the wire and crimped on a new terminal, but no joy. The connection on the sensor for the wire is clean.

It might help me to understand how the sensor works. Does it detect a ground through the coolant?

Thanks.

[Harvey Babb]

There are two types of coolant level sensor that I'm aware of. The one on my 2000 Endeavor works, as you suspect, by detecting the tiny current passing through the coolant to ground. The other type uses a thermistor that is heated by current. That passes current  to heat the sensor and detects the different amount of cooling of the uncovered sensor vs the cooling of the coolant. The "grounding" type will show low coolant if the sensor is disconnected and the thermistor type will show "normal" if disconnected. The thermistor type has to have a good ground to work, and gets hot enough to burn you if the business end is touched!

[bobdinsmore]

Not answering your question, but you may be able to fix the problem by polishing the sensor tip.

[Jim McGarvie]

7 hours ago, Harvey Babb said:

There are two types of coolant level sensor that I'm aware of. The one on my 2000 Endeavor works, as you suspect, by detecting the tiny current passing through the coolant to ground. The other type uses a thermistor that is heated by current. That passes current  to heat the sensor and detects the different amount of cooling of the uncovered sensor vs the cooling of the coolant. The "grounding" type will show low coolant if the sensor is disconnected and the thermistor type will show "normal" if disconnected. The thermistor type has to have a good ground to work, and gets hot enough to burn you if the business end is touched!

Good info, Harvey. Thanks. Would the thermistor type need two wires? Ours only has the one.

1 hour ago, bobdinsmore said:

Not answering your question, but you may be able to fix the problem by polishing the sensor tip.

Thanks Bob.

[vito.a]

If you have the one wire sensor, remove it and polish it with some scotch brite or steel wool.  I used to keep two sensors, one polished and ready and the other in the tank.  You will need to change them about every 6 months.  

[Jim McGarvie]

1 minute ago, vito.a said:

If you have the one wire sensor, remove it and polish it with some scotch brite or steel wool.  I used to keep two sensors, one polished and ready and the other in the tank.  You will need to change them about every 6 months.  

Thanks, but this is a new sensor. It may be defective, or maybe I have a break in the wire between it and the dash.

[jacwjames]

Do you have the part number of the new sensor that was installed?  When I replaced my surge tank I used a Ford sensor, which is a 2 wire, but I just combined the wires into one and attached it to the original coolant sensor wire. 

The chassis wiring diagram for my 2002 Windsor shows that there is a Low Coolant Module in the circuit which is what interprets the signal from the probe and turns on the light/bell alarm

Here is an IRV2 thread that discussing  https://www.irv2.com/forums/f115/low-coolant-light-on-but-coolant-is-not-low-340871-2.html

The thread indicates that it is a Kysor Alarm and that it is somewhere behind the dash and when I did a search I found this

https://www.wanderlodgeownersgroup.com/downloads/KYSOR ALARMS SERVICE AND INSTALLATION.pdf

 

[Jim McGarvie]

2 hours ago, jacwjames said:

Do you have the part number of the new sensor that was installed?  When I replaced my surge tank I used a Ford sensor, which is a 2 wire, but I just combined the wires into one and attached it to the original coolant sensor wire. 

The chassis wiring diagram for my 2002 Windsor shows that there is a Low Coolant Module in the circuit which is what interprets the signal from the probe and turns on the light/bell alarm

Here is an IRV2 thread that discussing  https://www.irv2.com/forums/f115/low-coolant-light-on-but-coolant-is-not-low-340871-2.html

The thread indicates that it is a Kysor Alarm and that it is somewhere behind the dash and when I did a search I found this

https://www.wanderlodgeownersgroup.com/downloads/KYSOR ALARMS SERVICE AND INSTALLATION.pdf

 

Thanks for the info, Jim. I don't have the part number; the sensor was included with a new tank. I haven't yet had a response from the source.

My schematic shows a low coolant module but it is notated "ISC only". We have an ISB, so I assume no module.

[Harvey Babb]

The thermistor type has two terminals, one of which is ground. That can be accomplished either with a second wire OR by screwing it into a metal tank that is grounded depending on the sensor. All that I have seen were grounded through the body and only had a single wire, but that was years ago. No idea what the modern ones look like.

A single wire thermistor sensor will show around 100 ohms if measured between the body and the connector.

A current probe will show infinite resistance between body and connector. The current probe usually sticks into the coolant an inch or more, while the thermistor is only about 1/4 inch.

 

[Jim McGarvie]

4 hours ago, Harvey Babb said:

The thermistor type has two terminals, one of which is ground. That can be accomplished either with a second wire OR by screwing it into a metal tank that is grounded depending on the sensor. All that I have seen were grounded through the body and only had a single wire, but that was years ago. No idea what the modern ones look like.

A single wire thermistor sensor will show around 100 ohms if measured between the body and the connector.

A current probe will show infinite resistance between body and connector. The current probe usually sticks into the coolant an inch or more, while the thermistor is only about 1/4 inch.

 

Good info, Harvey. Thanks. I probably won't be able to check those measurements without emptying the tank, which I won't get around to for a while. Hopefully I'll hear back from the supplier and will learn what type I have and how to check it.