Hydraulic Fan (For A/C)

[New Guy Will]

Do any of you guys know about a hydraulic fan (located in back drivers side behind radiator)? My Truck A/C is giving me trouble, and has a new Compressor, installed by Truck Pro. Brought it back to them, and they say this Hydraulic Fan is not working, and that allows head pressure to build up, and shut down compressor.
I believe this fan runs off hydraulics from the power steering resovoir.
Do any of you have any knowledge of this?
2000 Alpine 40FDS LE
Thanks, Will

[Old Scout]

Hours of reading on this forum regarding your issue. Early Alpines used a mechanical wax valve attached to radiator to control engine fan speed. Thus, no interface with the dash A/C requirements for cooling. Some owners live with it, some have added a solenoid to trigger fan with A/C system, some add electric fans with a relay from A/C system, and some have moved the condenser and added electric fans.
PS -- assume your Cummins engine is cooling correctly?

[wolfe10]

Yup, the fan is controlled ONLY by coolant temperature.


So, indeed, dash A/C head pressure can go very high if fan not operating.


In fact, when I needed to charge my A/C, I used a garden hose on the A/C condenser to keep temps in a range so that the A/C worked as it should.


There ARE some "work-arounds" including moving the condenser, installing electric fans (on either present location OR on relocated location (best) OR by modifying the hydraulic system so fan does turn some even if coolant temperatures are below cut in temp.


BTW, the modification to the hydraulic system to have the fan running even at cool coolant temperatures has a side benefit of lowering intake manifold temperature as air is drawn through the CAC.

[Bruce Anthon]

If your wax valve is working for your higher temperatures while you are on the road you can add a small valve in the line from the wax valve to the fan. With a strobe light you can set the minimum constant fan speed. I did it myself and was able to set the fan speed to 6-700 rpm’s. The valve is adjustable and the increased flow through the CAC is a plus. It solved the head pressure your shop has mentioned. I can look for some pictures if that would help you.

Take the time as Old Scout mentioned to review old posts. There are hours of them pertaining to this issue.

[Dave Fernandez]

Unfortunately, on the early Alpines with a Hydraulic Fan does not pull much air at Idle. This has caused many A/C compressors to destroy themselves. What some owners have done was to move the condenser to another location and use an electric fan that keeps the head pressure within the normal range. A few of us have installed an electric fan on the condenser and that has solved the problem of high head pressure.

[New Guy Will]

Originally Posted by Old Scout

Hours of reading on this forum regarding your issue. Early Alpines used a mechanical wax valve attached to radiator to control engine fan speed. Thus, no interface with the dash A/C requirements for cooling. Some owners live with it, some have added a solenoid to trigger fan with A/C system, some add electric fans with a relay from A/C system, and some have moved the condenser and added electric fans.
PS -- assume your Cummins engine is cooling correctly?

Yes Sir, Engine temp is fine, but the diesel takes a lot to overheat...
I believe what you are telling me is the engine temp is not getting hot enough to trigger the fan moter? I have noticed that when driving along at speed on the higway A/C fan speed needs to be on 3 or 'high", but when you slow down to go through a town, istop for red lights, A/C fan blows much harder, and you can set A/C fan back to low.
Does that seem consistent with what you are telling me?

[New Guy Will]

Thank you to all that replied, I was completely unaware of this design fault.
Will work on finding a solution. (Before I destroy this new compresssor)

[Old Scout]

Ref your post #7--looks like you have read all the inputs and now have a good understanding of the issue regarding lack of engine fan to dash A/C interface. Separate from that, you described a second issue with the dash fan. The front cab of Alpines is well sealed and with the air dam at the bottom, a partial vacuum tends to form in the genset area. As a result, the dash fan struggles to over-come the vacuum at hi-way speed but does ok in town. Solution is to keep the dash selector on "max air" at all times--this setting closes outside air dam and recircs inside air. Ironically, and for the same reason, this setting also works best for heating the front of the coach when driving in very cold weather.

[New Guy Will]

Originally Posted by Old Scout

Ref your post #7--looks like you have read all the inputs and now have a good understanding of the issue regarding lack of engine fan to dash A/C interface. Separate from that, you described a second issue with the dash fan. The front cab of Alpines is well sealed and with the air dam at the bottom, a partial vacuum tends to form in the genset area. As a result, the dash fan struggles to over-come the vacuum at hi-way speed but does ok in town. Solution is to keep the dash selector on "max air" at all times--this setting closes outside air dam and recircs inside air. Ironically, and for the same reason, this setting also works best for heating the front of the coach when driving in very cold weather.

Great Reply!! Solved a mystery, would never have figured this out alone.
Will

[Bruce Anthon]

These are some photos of the valve that will let you regulate the minimum engine fan speed. Very easy to install.

[Old Scout]

Ref post #10 picture, I am told there is an adjustment screw under the Allen-wrench cap on the wax valve that will increase the idle fan speed--but never tried it. Similar to the adjustment valves on HWH scissor slides, I like the needle valve solution offered by Mack Mover.

[Sideshow]

Bruce,
Thanks for the pictures, do you have a wider angle picture showing the location of that valve and how to get to it.
I just got the valve and need to install, hopefully get the AC working again
Cheers
Bob

[Bruce Anthon]

First, be sure to measure your fan speed cold, at idle, before you start the project so you have a reference point for your improvement. I got my RPM strobe reader at Harbor Freight.

The valve is located just under the top side radiator hose. That is on the top left corner of the radiator as viewed from the backside under the coach. It is a long reach but serviceable. Be sure to use two wrenches to support the valve as you break the fitting loose. Mine was very tight. You will also get some hydraulic fluid dripping so keeps some rags handy. I bought the two fittings you see in the picture that have the purple thread tape on them to go with the new valve. As I recall, when the valve was added, there wasn’t enough clearance to route the hose properly with the straight fitting that was on the original hose. I had a new one of a different length made up with a 90 degree end. I replaced the other hose at the same time as well. Both were getting stiff and hard by the fan motor. When you are under there you will see the the back of the fan, hoses and pipes that all have to be worked around. You might be able to keep the original lines… but this worked for me.

PM me if you would like to talk through the steps. Good luck!

[sandy1]

If you take the three bolts holding exterior radiator cover (painted) loose and you swing it up for easy access. If you lift it parallel to the ground it will drop out of hinge and can be set aside (use two people). 1/4” bolts are located on bottom between louvres and back end to rear cap