Engine heating question

[depchief]

Our Coach has the Cummins, ISC, 350 engine and I have been getting a light on the dash that is shaped like a key hole with an exclamation point. Asking Cummins people at Perry they could not answer as they did not bring a diagnostic computer to the show.
I have narrowed it down to what I think is a engine cooling issue. The light will come on about the time the temperature gauge reaches the mid point. Depending on weather conditions it will stay on or if cooler will cycle on and off.
The cooling fans appears to be working.
Do you notice an engine RPM change when the fan cycles?
Does the 4 wire connector on the cooling tank have a sensor that might trigger the light?
Does any one know what OHMS this sensor might read if good?

I have an appointment to take it in for service so any answers would be helpful

Thanks

[palehorse89]

A check engine light?

RV.Net Open Roads Forum: Dash Indicator Lights (Idiot Lights) - ???

[AFChap]

You are describing the engine fault warning light. The recommendation from the manual is to take it to a service center to find out exactly what the problem is. If the problem becomes severe, the engine may de-rate with reduced power and speed. Engine over-temp normally would be reported by a red light oat the bottom of the temperature gauge. Mid-point on my gauge is 175, about normal operating temp. I would not expect an over temp warning until 225 or over. The sensor in the surge tank triggers a low coolant light & alarm.

[Ray,IN]

That light should be explained in your chassis or engine manual. I remember seeing it in one of them, but don't remember what it indicates.