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Topic: Manual fan speed control for our 99 U270 (Read 960 times) previous topic - next topic

Manual fan speed control for our 99 U270

1999 U270 fan thermostat override

Finally got around to writing this up.

I had been thinking for some time about a remote override for the hydraulic fan control on our coach to increase cooling when we're using the retarder, or to get a jump start on the fan speed when we're starting up a long hill and know we will want full cooling before the engine temp gets up to 190 (where the fan temp valve starts to close.)

On our U270 (Cummins ISC) and maybe on all models of this vintage, the hydraulic fan speed control is a wax capsule-type thermostatic valve set into the return coolant pipe from the radiator.  Two hydraulic hoses connect the thermostat to a bypass valve on one of the dual hydraulic fans.  When the coolant temperature gets to about 190 deg, the normally open valve on the thermostat closes  and allows full flow to both fans for max cooling. 

This works OK when the engine is under load and engine temp increases, but my concern was that when we're going down a hill and sending lots of heat to the radiator from the retarder, the engine temp stays at 180 (no engine load), and the engine thermostat wouldn't be opened fully, so maybe the full flow from the engine water pump wouldn't be going through the retarder heat exchanger and the radiator, and maybe the engine hydraulic fan control wouldn't be on high speed or wouldn't be turned on as soon as would be desirable to keep retarder temps down.  I'm still not clear about whether the Cummins engine thermostat bypasses coolant flow from the coolant pump around the engine when the engine temp is below 180 (e.g. keeps flow through the retarder and the radiator, or simply restricts radiator flow like a car, but it seemed that being able to manually control the fan speed might get cooling started earlier than 190 deg going uphill, and might help with retarder temp going down.

This spring, when both Ken Hathaway and I were in Tucson, and Ken was debugging his fan hydraulic system problems,  I mentioned my project idea.  Ken had gotten to know his fan hydraulics and all the hydraulic shops in the city on a first name basis, and generously offered a tour of the hydraulic shops.

The project was simply to put a solenoid-controlled valve in series with the existing hydraulic thermostat, and wire it to a switch on the dash so I could run the fans on high when desired.  Sounded simple, but...

We went to several shops before finding one (Motion Control Technologies), that understood what I needed for my project, and could source the manifold and control solenoid for a low flow high pressure application (and could provide the adapter fittings for the connecting hoses (made up by another shop.) 

What I ended up with was a manifold (valve body) that had to be 2-way, since I wasn't sure which of the hoses to the hydraulic thermostat was the pressure side, a 2-way, normally open solenoid valve with a manual override to make testing easier, a 12v coil to control the valve, and various fittings and adapters to match the 1/4" hydraulic hose ends to the valve body and allow one of the hoses going to the thermostat to connect to the valve body.  We wandered around in Motion Control's supply room until we found the right fittings, tweaking things to match what they had on hand. 

Parts list (driven by what the vendor had on hand):
CBF - B08208S - Series 8, 2 way valve body (manifold)
CBF EV-08-23M-C solenoid valve, N.E., with manual override
12V DC DIN coil for valve
Various adapters for the valve body to connect to hose end fittings. 

I forget what the valve body fitting size was, but the hose connections to the hydraulic thermostat are a number 5 (5/16")  and a number 8 (1/2") gasket-seal type (ORB).  I had a 3' hose made up by another shop. 

Total cost for parts was about $140, which included a couple of adapters I didn't end up using.

Photos taken before I put the wiring in to the front (using existing spare wires.)

Unfortunately my experience with the control has been limited to one trip from Tucson up to Jackson Wyoming, where we've been sitting since May 12th, but on that trip I did observe lower temperatures on downgrades using the retarder, so I think it is helping.  More travel soon!



Dave and Nancy
1999/2013 U270 36' Xtreme
Motorcade # 16774
2013 Subaru Outback
KD0NIM

Re: Manual fan speed control for our 99 U270

Reply #1 –
Great idea. I was wondering if you could put a temp sensor in the circuit to trigger the valve in case you forgot to activate the manual switch.
Steve DeLange
2005 U320T 40'
Pearland, Texas

Re: Manual fan speed control for our 99 U270

Reply #2 –
Dave & Nancy,

Very practical mod.  Years ago when we had an overheating issue, we made many changes including putting a ball valve on the 190 degree hydraulic valve to manually force hydraulic fan motors into high speed, to see if the valve was not closing on high coolant temps.

But with your idea we will be able to anticipate heat gain.

Photo attached.

Re: Manual fan speed control for our 99 U270

Reply #3 –
Barry, I like it and added it to my list ^.^d
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My advice and experiences are Free, you decide if they are worth anything .

John - driving Old Faithful
1994 U280 GV
C8.3, Banks, Pacbrake, 900 watts, Resonator, XLHD tow dolly
Retired Army Warrant Officer

Life is what you make of it - if it is lemons, make lemonade!
Former Coaches:
1988 GV 40' ORED 300HP CAT - 9 years
1990 Winnebago LeSharo - 3 years
2000 Newmar London Aire - 3 years (#18 of 23 produced)

Re: Manual fan speed control for our 99 U270

Reply #4 –
Quote from: sedelange –
Great idea. I was wondering if you could put a temp sensor in the circuit to trigger the valve in case you forgot to activate the manual switch.

With the new bypass control in series, the existing hydraulic thermostat still works the way it used to.  With the bypass control off, when the temp goes above 190, the thermostat starts to close and fans run on high.  If the new bypass control is already on (hydraulic circuit closed), fans are already running on high.
Dave and Nancy
1999/2013 U270 36' Xtreme
Motorcade # 16774
2013 Subaru Outback
KD0NIM

Re: Manual fan speed control for our 99 U270

Reply #5 –
Dave,

Someone once told me that if you simply unplug the hydraulic fan's electric wires from the engine controller in the engine compartment, the fan will default to high speed. If that is true wouldn't it be easier to make this disconnection with a multi-pole relay controlled from the driver's seat.
Jim Frerichs
2002 U320 42'

Re: Manual fan speed control for our 99 U270

Reply #6 –
Interesting thought, but I would bet that taking that sensor out of the loop will throw a check engine light. Maybe not a deal breaker if it clears itself when you re-engage it... but the enunciator would make me want to do terrible things :-\
Don
Quote from: Jim Frerichs –
Dave,

Someone once told me that if you simply unplug the hydraulic fan's electric wires from the engine controller in the engine compartment, the fan will default to high speed. If that is true wouldn't it be easier to make this disconnection with a multi-pole relay controlled from the driver's seat.
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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: Manual fan speed control for our 99 U270

Reply #7 –
Quote
the hydraulic fan speed control is a wax capsule-type thermostatic valve set into the return coolant pipe

@Jim Dave's high/low switch is a mechanical switch. With his modification he added a solenoid to control it electronically (via a switch) from the drivers seat.

My coach (and I believe the majority of Foretravels) use a solenoid activated by a thermostatic controller on the engine. The controller normally activates a solenoid that causes a percentage of hydraulic fluid to bypass the fans and go directly back to the reservoir. When the engine hits a factory set temperature the controller cuts power to the solenoid which closes the bypass of hydraulic fluid directing it all to the fan(s). So your statement is correct for solenoid controlled coaches pulling the wire will result in fan(s) staying in high speed mode.

A switched relay is exactly what I'm planning to use on my coach. Once I have it in and tested I'll post a write up and of course pictures. :) Unless of course someone else out there is itching do it first! It will be next week before I get to it.

@Don I've pulled the controller wire before and it didn't cause a check engine light for me. YMMV :) Very easy to test.

BTW: if your high/low switch has been disabled like mine was by the PO it is a very good idea to reconnect it. 

see ya
ken
The selected media item is not currently available.ken & dori hathaway & Big Agnes
🍺1992 U300 GrandVilla WTBI #4150 FOT FBP 2011
✨6V-92TA DDEC Parlor Coach 350HP Series 92
🏁2011 Nissan XTerra Pro-4X

Re: Manual fan speed control for our 99 U270

Reply #8 –
On my 95 U240 the high/low fan speed is controlled by a electric solenoid.  The solenoid is controlled by a temp sending unit (just like temp gauge) and on the engine just below the temp sending unit for dash gauge.  The sending unit keeps the high/low fan solenoid energized by appling +12v to have low speed fans.  I disconnected the ground side of the high/low solenoid and used to spare wire already running to the dash.  Installed a single pole single throw rocker switch in spare position on the dash. One side of rocker switch goes to the spare wire going to high/low fan solenoid and the other side of the rocker switch goes to any ground.  If you leave the new switch on low and the engine needs high speed fans the  temp sending unit will drop 12v from the high/low fan solenoid and fans will go into high speed.  If you see a need for high speed fans for additional cooling in prep from long uphill grade or other reasons turn the new switch to "off" position, disconnecting the ground from the high/low fan solenoid and making the fans go into high speed.  Works great for me.  My only problem now is to upgrade my dual fan motors, already replaced the pump and sun controller trying to get max fan RPM .  I am waiting for FOT to get all the parts and motors, hope to get them by Oct 17.

Pat,
Pat/Blue Angel
1995 U240 36ft
MC# 16511
Build# 4653

Re: Manual fan speed control for our 99 U270

Reply #9 –
Quote from: Jim Frerichs –
Dave,

Someone once told me that if you simply unplug the hydraulic fan's electric wires from the engine controller in the engine compartment, the fan will default to high speed. If that is true wouldn't it be easier to make this disconnection with a multi-pole relay controlled from the driver's seat.

Ken is right - no electrical controls for our fans.  Not sure how many engines are set up this way, but for sure, if we had an electrical solenoid control, that would be the easy way to put in a manual control.
Dave and Nancy
1999/2013 U270 36' Xtreme
Motorcade # 16774
2013 Subaru Outback
KD0NIM

Re: Manual fan speed control for our 99 U270

Reply #10 –
Does anybody know if the hydraulic thermostat (in the total mechanical control fan system) is on/off or variable flow rate. Said differently for the electrical brained people--is it digital/discreet or analog?

Also, an easy way to tell which hose to the thermostat control valve is supply...just take off one line and aim both openings to a bucket and breifely crank or start the engine. It won't be high pressure with the line open.
1998 U270 34'
 

Re: Manual fan speed control for our 99 U270

Reply #11 –
Variable is my understanding
"Riding and rejoicing"
Bob
1997 U320 40' Mid entry, build 5132,  wtbi ce27, 4th owner
2007 Solara convertible
2 prodeco tech outlaw ss electric bikes

1095 watts solar
08 Ls 460 and a sc430
2000 Ford F-250 superduty 4x4