Community Forums

grldst · 04-13-2017, 09:53 AM

I have a 2002 Executive RR10S chassis with a ISM Cummins. It has twin hydraulic driven cooling fans for the radiator.

Question 1...are these fans variable speed or are they just low/high speed?

Question 2...The fans do not speed up when the dash Air conditioning is turned on...are they supposed to?

Question 3....is the only control for fan speed a temperature sensor in the radiator or is their another sensor/control to regulate fan speed when the AC is on?

Note: On a recent 5000 mile trip, engine runs at normal temps, so I'm assuming the hydraulic fans are working correctly to keep engine cool.

Old Scout · 04-13-2017, 10:09 AM

From my experiences, many 2000 era coaches used a mechanical wax valve to control fan speed and interface fan with engine temps--thus no interface with dash A/C needs for condenser cooling [this all assumes your A/C condenser is co-located on the radiator stack vs remotely located with electric fans, somewhere else on the coach. By mid-2000s, manufacturers were using electronic fan controllers with a built-in A/C interface.

grldst · 04-13-2017, 03:10 PM

Yes, my AC condenser is stacked with radiator.

Is it possible to convert the fan speed regulator to the newer electronic version, or are we talking a whole completely different hydraulic fan setup, not just the fan speed regulator.

William Willard · 04-13-2017, 04:40 PM

You`re better off with the wax valve - The electronic version can be more of a problem & some have converted to the wax valve -- If it`s cooling OK, don`t try to fix something that`s not broke -- I speak from experience -- Bill Willard

grldst · 04-13-2017, 05:38 PM

It's not engine cooling that's a problem...it's AC pressure when the engine is at idle. The AC system will build pressure into the 400 to 500 range.

Just got thru changing a blown line. When they recharged the system they noticed that the fans don't speed up when the AC compressor engages, and the system exceeds acceptable pressures.....so I'm wondering if this is normal for my motorhome or if there is something that is not working correctly.

Old Scout · 04-13-2017, 06:52 PM

Not all coaches of that era are alike but here are some options. First, do agree the electronic controller has its own set of issues, so if engine cools, don't mess with it. Options: 1-add electrical solenoid to fan motor fluid control line, relayed to the A/C compressor clutch circuit; 2-if space allows, add electric fans to outside of condenser on stack [again relayed to A/C clutch circuit]; or 3-move condenser from stack and relocate forward to cleaner/cooler air--again, add electric fans relayed to A/C clutch circuit.

CJScepter · 04-13-2017, 08:34 PM

I have a concern too, with the cooling of the AC condenser, at this time I just try not to use AC when driving very slow or at idle, To me the easiest fix would be to add an electric fan to the stack of radiators, controlled by a switch of its own or wire to the AC control switch.
I had a 1999 Monaco Diplomat that blew some freon past a seal, I found the electric fan was bad and replaced it, it was easy, found exact fit at summit racing, did have to replace connector.
John G

Daytonaman · 04-13-2017, 11:30 PM

It is a known fact that the wax valve system does not activate when dash AC is on; this is usually not a problem for my 02' Sig as the fans run at slow speed anyway. When it is >90 out, they get moving.
I charge my system @ idle ambient to system specs, and hi-side pressure never gets beyond limits. Enough refrigerant stores in the receiver.