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Old 01-11-2010, 01:20 AM   #1
Richard and Rhonda
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Join Date: Oct 2007
Location: Huntington WV
Posts: 1,041
Default Hydraulic Fan Control

On a couple of recent trips I noticed the engine temp (Series 60) was running consistently at 180, and the tranny and oil temps were following very closely. That was interesting because the engine temp had been running right at 200 and the tranny at 205. Since I had recently sprayed the radiator with degreaser and rinsed it, I wrote it off to a cleaner radiator. I was getting these numbers from the VMSPc so I tended to believe them.

Then on the recent run back to Texas from SC, the tranny temp got all the way down to 150, which is too cool. Something wasn't adding up about this odd behavior. Then after one rest stop, and an engine restart the whole shebang started running at 200 again. However after the next shutdown and restart it returned to 180. Weird.


But I did notice that my fan ran all the time now, even when I first cranked the engine. That didn't seem right to me.

I learned a bunch of new stuff, maybe some of it will help you some day.

The fan is controlled through a manifold that is mounted at the lower right of the engine as you face the rear. It is easliy found since the big hydraulic hoses that go to the fan motor go right through this manifold. You will also notice there is a solenoid valve on the manifold with a a two wire electrical connection.

When the solenoid is open the fan does not run. The fail safe position for the system when the solenoid is closed OR inoperable is for the fan to run at it's max speed. That makes sense. If you look carefully on the backside of that manifold block you will see a second valve with a screw adjustment for controlling max fan speed.

Anyway the coil on my solenoid valve had failed, so the fan was running all the time and keeping the engine too cool. I found in the DD service manual, the thermostats start to open at 182 and are wide open at 207, target operating temp for a Series 60 is 190 according the manual. I knew the coil was bad because an ohm meter showed no continuity through the coil. The new one showed right around 7 ohms resistance.

Newell shipped one to me for thirty bucks. I could have sourced it locally or via the internet if mine had any identification. The writing was long gone :-) After I got the new coil I searched around and found a cheaper one, yep 4 bucks cheaper. I really like it that Newell doesn't gouge you on parts.

Also, I learned that those electrical connections that Newell uses are made by Packard, and are called Weather Paks. You can get them in many places on the net, seems they are a standard high performance DC connector.

When I installed the new coil, the fan stopped turning at startup. Just for grins I disconnected the coil and the fan started again, so that confirmed the problem.
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Richard Rhonda Ty and Alex Entrekin
1995 Newell # 390 DD Series 60, Allison World Trans
Subaru Outback toad
CoMotion Tandem
Often wrong, but seldom in doubt
Rhonda's chronicle https://wersquared.wordpress.com/
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