First post here We have a 2005 Peterbilt 335 water truck with a Cummins engine. The engine fan clutch runs all the time no matter what. When I put my meter on the two pin connector going to the air fan control solenoid I get 10.88 volts. Ground wire checks out good when checking continuity to chassis ground. If I jump 12 volts to the control solenoid the fan clutch disengages like it’s supposed to. We have replaced the ECM, fan control solenoid, and the fan clutch itself. Having trouble finding a good wiring schematic other than what Diesel Laptops provided me with. Any thoughts or input is appreciated… thanks.
Have you checked fan relay and fuse in power distribution panel? Does this truck have a manual switch?
Which engine? 2005 is long enough ago that I am not sure if the fan clutch is controlled by the ecm. Had a Freightliner water truck last week (with a c7) with the same problem. That one turned out to be a faulty a/c selector switch.
Could not find a fuse for “engine fan” or fan control. Dash has a switch that toggled between “auto” and “on” I pinned out the switch and it has 12 volt supply and sends 12 volts out depending on which way it’s toggled. Engine is the ISC315. Thanks
I just put in a fan switch and f the computer. Going to do it to a Western star possibly tomorrow too
I do not have very much experience with that engine. In fact almost none other than I looked at buying an RV with that engine a few years ago. Iirc, that one had a variable fan drive that was on low almost all of the time and would kick into high when the temp hit a certain point (maybe 210f*). Not sure if you have the same set up. It had a fan clutch sensor. If you have one check for power there. Think a blown fuse in the sensor sensor circuit will keep the fan stuck on high as a default setting. In all honesty my lack of familiarity with that engine and a funny smell in the bedroom helped me to decide that I didn't really want an rv.
Three things I know of that will keep that fan locked in: (1) low air pressure (2) a/c high pressure switch (3) coolant temperature. Same engine I have in my 2007 kenworth.
Correct--Problem is in those years fused power wasn't always separated. And #4 electric over air solenoid.
Appreciate all the input you guys. Does anyone have a schematic for this truck I could use? Having trouble finding one.
last six of s/n?
Yeah, low air pressure. That's another good idea. Had that on another tractor. Have you tried supplying shop air to the fan clutch? I had one a couple of months ago with the fan stuck on and only found the leak when I was working my way back to the solenoid and supplied air from there.
The specific place I saw low air pressure causing issue was with a 2011 Pete 337, the cut in on the air governor was out of adjustment allowing the air pressure to go below what it takes to keep the fan off on that particular truck, 100 psi if I remember correctly. Pressure would drift low, fan would come on until the compressor kicked in and brought the psi back up. Took quite a few miles before I was able to pinpoint why it was doing it.
Last 6 of truck vin is 857391. I don’t believe it’s a low air pressure issue because this truck builds close to 120 psi just fine. Fan clutch works when I jump 12 volts to the fan clutch control solenoid. If it was a low air pressure issue I don’t believe it would disengage the clutch even when I jump power to it. Thanks.
In my years--I have never seen a fan that used 100 psi to stay clutched or unclutched. Cold start up building air fan will engage till psi reaches a required 80 psi. Other wise fan hub is leaking.
Never seen it before or since truckshop. Just know I was in the driver seat and that’s what was causing it and that’s what made it stop.
Diagrams attached. Any check engine lights on? ECM coolant temp, intake temp and a/c will turn on the fan. The temps you see in the gauges are separate sensors from what the engine sees. If you could get a laptop on it the computer will tell you want switch/sensor is commanding the fan on. Also the 10v you are seeing at the connector is just stray voltage, there is no amperage there at all. Try using a test light, it wont light it. So just ignore the 10v
Forgot about intake temp--that is common issue with the DD15--sensor or rubbed harness.
Having this same issue on my 07 335. Believe it’s making my ac compressor not run either. Ever find the solution?
Cummins ended up plugging into the truck and found that the ECM was factory set to run fan all the time. They reflated it and no issues since.
They re-flashed the computer***
Lol I did this then got tired from that job a few days later, never got to enjoy the more quiet engine.