Q. The Cooling Fan on my Country Coach seems to be acting somewhat erratically. Recently I was on a trip and after the engine reached its operating temperature the gauge showed the coolant temperature cycling from 191 to 202. After a few miles, it went back to the normal cycle range of 187 to 197 degrees. Later in the same trip, I noticed the coolant temperature went crazy and shot up from 181 degrees to 202 degrees, then after 10 to 15 miles it came back down and maintained the temperature at 195 degrees. The air conditioning was not running through any of this, any thoughts as to the problem?
A. The fan controller uses a technology called open loop proportional hydraulics. This essentially means that the fan speed is infinitely variable by the electronic fan controller. The controller is a “normally closed” solenoid, meaning, loss of 12v power to the controller will cause the fan to run at full speed at all times.
The following scenarios could explain symptoms of erratic behavior:
1. The fan controller is requesting an incorrect fan speed based upon erroneous information from the coolant temperature sensor and/or charge air temperature sensor inputs. This could be a problem with loose or corroded connectors at the sensors or at the fan controller which is located on the rear end of the radiator package. It could also be due to a damaged harness to the sensors or defective sensors. Given the low cost of the sensors it is probably advisable to replace them both as a matter of course after first checking all the connectors, harnesses, and ensuring good power and ground in the next step.
2. The fan controller is not receiving adequate voltage from its two pin connector. One contact in this connector should have a minimum of 12V when the ignition system is powered up. The other contact should show less than one ohm resistance to a clean frame ground.
3. There may be a problem with the fan controller programming and this would need to be verified by Country Coach Corporation’s service department.
4. The fan controller is requesting the correct fan speed but the proportional valve on the controller or the switch valve on the fan motor is not responding properly. This is fortunately very unlikely but would need to be diagnosed by Country Coach Corporation’s service department.
5. The fan cooling system is operating correctly but is responding to inconsistencies with the coolant or charge air temperatures. The coolant temperature shouldn't be an issue here unless there is a problem with the engine thermostat. The charge air temperature however may cause these symptoms if the air filter is plugged or you may be loosing turbo boost pressure due to a leaking boot at one of the large diameter tubes between the turbo charger and the intake manifold.
Please note that the coolant temperatures quoted above are not typical of all coaches. Normal operating temperature will vary with engine manufacturer and age. The general trend is for newer engine designs to run hotter as the manufacturers seek to reduce emissions and improve efficiency.
Source: Service Tech staff at the former Country Coach LLC provided this helpful info to the Country Coach Friends Incorporated motorhome owners club which is still pertinent to CC owners experiencing a similar problem today.
For additional help with this issue you may contact your local Cummins or Cat engine service center for troubleshooting tips.
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