[Yachts]

I just returned from Creede Colorado , and during the mountain driving I un hooked the fan relay in back so it would run high all of the time. I noticed the following during a 7 mile climb up a significant grade pulling a stacker weighed at about 17500, the highest I got was 217 degrees. I did manually keep the RPMs in the 17-1800 range. It hit 217 briefly twice then backed down. 

Conversely 2 years ago similar grade actually got a little hotter than that without unplugging fan.. 

Question is there a reason to have it run 2 speeds would hi all the time be better not just in the mountains.?

[jcus]

On high speed, your fan would typically use 50 to 60 hp. At low speed probably only 30 or 40. The ecm should read engine perimeter's and adjust fan speed accordingly. You need all the hp you have with a big trailer going uphill. On the flats, low speed is better because you are not using the extra hp just to run the fan on high when temps do not require it, saving fuel, and giving up the extra 20 or 30 hp if you need it.

[encantotom]

marc, 217 is higher than i have ever seen, even going up and over steep mountain passes.

but...i am not pulling a 17,500lb stacker.

i spent some time researching online about what temp the CEL and then later the SEL comes on.

it seems that 217 is what most say for CEL. and for SEL, i have seen 222, 235 and 240 listed.

so, any experience on the temps for cel and derating?

thanks

tom

[Richard]

Marc,

When the fan speed control solenoid fails, it fails in the high position. That's a good safety feature.

Mine failed a couple of years ago, and I noticed that the fan running on high all the time cut my mileage by 0.5 mpg. This agrees with Jimmy's data on the HP that the fan uses.

[jcus]

Marc,

When the fan speed control solenoid fails, it fails in the high position. That's a good safety feature.

Mine failed a couple of years ago, and I noticed that the fan running on high all the time cut my mileage by 0.5 mpg. This agrees with Jimmy's data on the HP that the fan uses.

http://www.rvtechlibrary.com/engine/Cat_...rmance.pdf

[encantotom]

.4 mpg increase slowing from 70 to 65

That is significant

Tom

[Yachts]

when I first bought the coach, the solenoid failed controlling the fan speed. I got a cel at 218 and sel at 222..

[jcus]

when I first bought the coach, the solenoid failed controlling the fan speed. I got a cel at 218 and sel at 222..

I guess i do not know how my hyd fan works, when water temp is below 190 I have no fan, { i can tell because charge air temps are high],
and at about 198, fan come on, charge air temp and water temps drop immediately till water temp is about 194, then it rises again and repeats cycle.
Do we have an hi-low-off system?, if so must be a 3 position solenoid, which I have never seen. I have only two wires into the solenoid.
Anyone know how it works?
Jim

[jcus]

when I first bought the coach, the solenoid failed controlling the fan speed. I got a cel at 218 and sel at 222..

I guess i do not know how my hyd fan works, when water temp is below 190 I have no fan, { i can tell because charge air temps are high],
and at about 198, fan come on, charge air temp and water temps drop immediately till water temp is about 194, then it rises again and repeats cycle.
Do we have an hi-low-off system?, if so must be a 3 position solenoid, which I have never seen. I have only two wires into the solenoid.
Anyone know how it works?
Jim

In reading past posts, it appears some coaches have only an on/off, on the engine cooling fan. I believe that is my case. The reason my charge air temp rises so fast when fan is off,  is because the intake into the cac is right above the turbo to exhaust line and I have dumped the heavy blanket and am using a wrap. I guess I will need a new blanket or I can insulate the cac piping.

[Richard]

Jim,

Take a look at the aluminum manifold block where the solenoid is located. I think you may find an adjustment screw for the low speed circuit. I think, but I'm not sure, that you could increase the fan speed by backing out that screw.

I also think, but don't have the data to prove it, that the reason that we are all over the board on the low fan speed is that it could have been set differently at the factory, or age and miles have altered the fan motor, hyd pump pressure, or orifice in the low speed circuit.