Community Forums

bharrisv65 · 06-03-2019, 04:12 AM

Hello all! We just bought a 2017 Tiffin Zephyr with the 600hp Cummins and while traveling out west, the fan clutch went out which caused the MH to run hot. Had to wait 2 days to get the FC to the shop and installed. Left late on Friday, drove about 30 miles and the MH was running hot AGAIN. Discovered as long as I drove no more than 60 mph and not run the engine AC, it would stay in the normal range. Made it back 180 miles to Albuquerque, NM and left it in a KOA for the holiday weekend. On Tuesday, took it to the Cummins dealer who checked T-stats, anti-freeze, temp sensor, etc. Ended up it was a blown fuse for the fan clutch. The original fan clutch was bad, I know that for a fact as the bearing had failed. The MH and engine only have about 20,000 miles on it so just curious if any of you who have the 600hp engine have had any problems with the fan clutch? Mine is the side mounted radiator. I did learn (at a cost of approx. $1000) when the fan clutch kicks in while running the ac and also not running it as the gauge will climb to a certain point, you can almost hear/feel the fan clutch kick in and see the gauge start to move lower. My temp gauge is set up like a fuel gauge with cold, 1/4, 1/2, 3/4 and hot increments. With the ac on, the fan kicks in just above the 1/4 mark and the MH will run 'normal' temp at just above that 1/4 mark. With the ac off, running above 65 mph and not running just on flat ground, the MH runs close to the 1/2 mark and the fan clutch will kick in when the needle goes just above the 1/2 mark. So, I'm wondering if this is where your unit runs so I'll kind of know if this is typical. Sorry for the long winded post but I wanted to describe the issue in full so I can get as much info as possible. Thanks! (BTW, this 600hp engine is a beast when it comes to accelerating and pulling steep grades! WOW! That poor old V10 gasser I had previously would struggle up every single hill we went up while this one hardly even downshifts or loses speed!)

**Lt Dan** · 06-03-2019, 08:34 AM

Since your 2017 doesn't have the new advanced dash display, I would recommend you get a ScanGauge D or Silverleaf monitor. That will let you see the coolant temperatures more accurately. Normal operation is for the temps to rise to about 210 then the fan will kick into high speed mode. The temps will drop into the 185-190 range and the fan will go back to low speed. That 600hp engine will generate a lot of heat and will probably go through the up and down cycles a lot more frequently.

Mr_D · 06-03-2019, 09:20 AM

I have a Silverleaf VMS 400 CL in my rig. I monitor the coolant temp, the transmission fluid temp and oil pressure at all times. Mine runs right at 188° unless on an up grade. I did see it get to 192° once.
This was on a 4,800 mile trip right after it's third head replacement. I ran it hard as it has a one year, 100,000 mile warranty and I am trying to trust it not to break a valve off as the older 650's are known for.
I suggest you get some kind of monitor that gives real time accurate temps. such as the Silverleaf monitors. Very helpful to know the information that a readout gives.
BTW, I agree with the power even though the Allison gear spread in 5th and 6th is too wide.

JMonroe · 06-03-2019, 03:37 PM

I assume that fan clutch was covered under the chassis three year warranty?

bharrisv65 · 06-03-2019, 03:56 PM

Quote:

Originally Posted by JMonroe

I assume that fan clutch was covered under the chassis three year warranty?

It would have been but we were 180 miles from the nearest dealer and it was late Wednesday before we could get it towed to a local shop. My extended warranty paid for most of it, what I had to pay was special handling top get it overnight into Albuquerque then I had to pay $290 for someone to hotshot it direct and expedited to the local shop. As it was, they had me out the door at 5:05 PM on Friday of a HOLIDAY weekend so I was lucky (or so I thought) to get it "fixed" and not have it sit in that shop until Tuesday. When I took it to the dealer in Albuquerque and they diagnosed the blown fuse, that was not under the chassis warranty.....that cost me $300 (hooking up and running diagnostics) but believe me, when you're able to drive away and not have the temp gauge pegging out, it was worth it!

bharrisv65 · 06-03-2019, 03:59 PM

Quote:

Originally Posted by Mr_D

I have a Silverleaf VMS 400 CL in my rig. I monitor the coolant temp, the transmission fluid temp and oil pressure at all times. Mine runs right at 188° unless on an up grade. I did see it get to 192° once.
This was on a 4,800 mile trip right after it's third head replacement. I ran it hard as it has a one year, 100,000 mile warranty and I am trying to trust it not to break a valve off as the older 650's are known for.
I suggest you get some kind of monitor that gives real time accurate temps. such as the Silverleaf monitors. Very helpful to know the information that a readout gives.
BTW, I agree with the power even though the Allison gear spread in 5th and 6th is too wide.

I agree, I don't like just "marks" on a gauge, I'd rather see actual numbers. I'm going to check into the monitors you suggested, thanks. Oh and good luck with your issue, that's ridiculous having had three heads replaced!

bharrisv65 · 06-03-2019, 04:07 PM

Quote:

Originally Posted by Lt Dan

Since your 2017 doesn't have the new advanced dash display, I would recommend you get a ScanGauge D or Silverleaf monitor. That will let you see the coolant temperatures more accurately. Normal operation is for the temps to rise to about 210 then the fan will kick into high speed mode. The temps will drop into the 185-190 range and the fan will go back to low speed. That 600hp engine will generate a lot of heat and will probably go through the up and down cycles a lot more frequently.

I agree on the gauges Lt. Dan. Yep and you're correct on your comments about when the fan kicks in and that it cycles fairly often. What's really odd is I drove it 180 miles with the fan not working at all and it never ran more than at the 'normal' mark (just a tick above the 1/4 mark) except once when I ran my speed up above 60 and then it only went up about to half but came back down pretty quickly. I know it would run hotter pulling hills, luckily I40 from Gallup, NM to Albuquerque is relatively flat with very few hills of any height, it was in the low 70's and approaching night time.

garykk · 06-04-2019, 06:12 PM

So you had the fan clutch replaced and it still ran hot??? Did not this shop test drive your MH for more than a trip around the block??? How they could pass this with a blown fuse is amazing.

bharrisv65 · 06-05-2019, 05:47 PM

Quote:

Originally Posted by garykk

So you had the fan clutch replaced and it still ran hot??? Did not this shop test drive your MH for more than a trip around the block??? How they could pass this with a blown fuse is amazing.

They didn't test drive it but said they let it run at a fast idle for about an hour. In their defense, I think the fuse may have blown AFTER I left when the fan clutch was replaced. I say this because, I drove over 30 miles running 70mph and with the a/c going before the temp started rising again. It ran normal within the first 25 miles or so then the temp gradually started to rise, but I did start slowing down and cut the air off. When I took it to Cummins, they didn't test drive it either which really ticked me off because I thought I was going to have another instance but lo and behold, the fuse cured the issue and we drove 1800 miles home with no more problems.