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Topic: Fan RPM (Read 1179 times) previous topic - next topic

Re: Fan RPM

Reply #20 –
Sounds like we may have an answer - FOT and Cummins got on the phone together and it appears that when we had our rig in for the hydraulic fan motor replacement back in August (independent hydraulic shop that stayed open late and was hurrying to get us back on the road quickly since we are FT in our coach), they installed it backwards (thanks to those who suggested that as a possibility) ... Now they are trying to figure out why RPM are so low, but at least they know why one was running in reverse ... no wonder our overheating issue seemed to get a little worse this last trip across the country... Thanks again - I'll update once we have more answers...

Re: Fan RPM

Reply #21 –
As discussed, straighten out the hose routing before concluding that fan speed is incorrect.

And, let us know if you have the electronic or wax valve hydraulic control for fan speed.

Re: Fan RPM

Reply #22 –
Quote from: wolfe10 –
As discussed, straighten out the hose routing before concluding that fan speed is incorrect.

And, let us know if you have the electronic or wax valve hydraulic control for fan speed.

Per the control - Foretravel replaced the control unit last year - it was a $1k part - little silver box that sits on the frame at the back of the engine - Does that identify it as the electronic?  I assumed so.  And yes, I'll update once they have the hoses running in the right direction ...

Thanks again, Tim

Re: Fan RPM

Reply #23 –
The danfoss control unit with input from the ECM manages the desired fan speed when functioning normally with the solenoid valve installed on it. Typically fails to fans stuck in hi speed position with actually some benefits like cooler bedroom and improved retarder function by improved cooling temperature offset by the increased fuel consumption to run the fans in Hi.
Resolve your fan direction issue before continuing on trouble shooting and spending money needlessly. The Tech that installed your replacement danfoss control unit should of verified visually that fans would ramp up with engine at hi idle and disconnecting controller by seeing/hearing  fan speed increase. During my original coach purchase I came across this problem as fans were maxed out all the time. Drove 7500 miles till i could perform repairs with the added cost of the fans running at hi.
Hydraulic fan controller DIY
This has worked well for me and I would duplicate again.
Resolve the rotation issue first . Your lines may or may not be routed correctly, ie motor could of been assembled to operate backward while apart possibly (unknown)

Scott

Re: Fan RPM

Reply #24 –
Once the hoses were routed correctly, both the fans spun in the same direction and it passed the heat test on the dyno at Cummins - The fans, according to the hydraulic shop that rebuild them (Weis?)  will run at 1/2 engine RPM, when needed (above thermostat temp of 185°f)  Due to this they were only running at 1000 RPM - They said the fans are capable of reaching 3000 RPM (as per the Foretravel document above)  but they rarely will do so.

Hoping this is the last of our overheating issues - we pick up our coach on Monday after they get the step back from the body shop (a tow truck ran into it while it was at Cummins )  and I can do some prep work to get back on the road again.  While we are grateful for family that let us stay in their guest room, after 4 months we are ready to be back in our home again! 

Thanks again for all the advice and help here.

Aloha, Tim

Re: Fan RPM

Reply #25 –
Just wanted to give one more update after driving 800 miles the last 2 days, including lots of rolling hills, 80° outside temps, 3 hours of stop and go Atlanta & Chattanooga rush hour traffic - We arrived at FOT last night and the water temp never rose above 181° - and then only for a couple seconds until it dropped in the upper 170's.

Better yet is our fuel mileage - went from 6.5 to 8.5!  the cost of driving for engine survival vs fuel economy plays a big part in that I'm sure.

Can't wait to drive over the Rockies now.

Currently we're at FOT for fuel line replacement - if you're here stop by and say "hi" - we're the only 36' U320 in the parking lot 🙂 - I can show you what a lot of new parts looks like in the engine bay lol

Thanks again for all the help getting this issue resolves (it's been a long 18 months getting this resolved)

Aloha, Tim
 

Re: Fan RPM

Reply #26 –
Thank you for the follow up. Glad to hear that issue is done 👍