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Old 11-22-2022, 08:49 PM   #1
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DEF Light

Got the dreaded Def light on my 14 37AP Bus on my way home from wknd trip. Left the RV Park went 3 or 4 miles and noticed def guage was on E . I knew I had About 3/4 tank of Def. Drove about 50 miles with guage on E so decided to pull into a Loves and top off the Def to see if it would maybe shake up the guage but stayed the same. The Amber lite had came on about 15 Min. before I stopped. Ckd the code 1671 . I didnt shut it off . Drove on home abt 40 more miles guage on E Amber lights on. Was only a very slight reduction in power . I was hoping not to get the full De rate. Got home and backed in garage shut it off . went back out and started it 10 mins later Def guage bounced to full lights went off. Ckd for codes today no codes present. Ordered a new Def head from Tiffin it will be here Tuesday. Looks pretty easy 4 Bolts that hiold the plate in that tank rests on. Lines look a little tight on top being there is a bunch of other hoses going over them. Has anyone did this job ?
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Old 11-22-2022, 09:56 PM   #2
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I changed the head out on our Phaeton and it required dropping the tank out of the bottom but yours may be different. Getting the head out of the tank took some careful prying but overall it's not a difficult job. You will need a 1/2" plug to stop the coolant flow or pinch the hose off with a pair of vise grips. There's really no way to salvage the DEF in the tank so just plan on replacing it.
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Old 11-23-2022, 05:58 AM   #3
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Quote:
Originally Posted by Dsrtrider View Post
Got the dreaded Def light on my 14 37AP Bus on my way home from wknd trip. Left the RV Park went 3 or 4 miles and noticed def guage was on E . I knew I had About 3/4 tank of Def. Drove about 50 miles with guage on E so decided to pull into a Loves and top off the Def to see if it would maybe shake up the guage but stayed the same. The Amber lite had came on about 15 Min. before I stopped. Ckd the code 1671 . I didnt shut it off . Drove on home abt 40 more miles guage on E Amber lights on. Was only a very slight reduction in power . I was hoping not to get the full De rate. Got home and backed in garage shut it off . went back out and started it 10 mins later Def guage bounced to full lights went off. Ckd for codes today no codes present. Ordered a new Def head from Tiffin it will be here Tuesday. Looks pretty easy 4 Bolts that hiold the plate in that tank rests on. Lines look a little tight on top being there is a bunch of other hoses going over them. Has anyone did this job ?
That's interesting, the codes that typically show up concerning the dreaded DEF head failure that has bitten a lot of us are 3364, 1761, and 3031. Is it possible that you inverted the 1761 (DEF tank level) to the 1671 in your post? Based on the age of your coach (pre mass DEF head problem) and the single code that you are getting, even if 1761, I wonder if there may be something else going on? I really like Dan's advise about replacing the DEF currently in the tank since it really could be a DEF problem and not the DEF head problem. Finally, here's a link to a very good article written by Mark Quasius for NIRVC concerning the mass DEF head problem: https://www.nirvc.com/blog/def-head-...exhaust-fluid/
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Old 11-23-2022, 05:34 PM   #4
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I had this happen on our 2014 Allegro Bus 37AP as well this summer. I had a half tank at the time it went to E. I added 5 gal, and it went back up to full. It now just stays between full & 3/4.

What I find out is our MH is only looking to see if there is DEF in the tank. It isn't checking quality, which is the issue that is causing people to replace the DEF head. I suspect you just have a stuck DEF level float/gauge in the tank. (Google that and you'll see how to clean it. And to minimize it reoccurring, you should keep you tank 3/4 - full.)

I spoke to Gary Harris, Tiffin chassis manager, who wasn't quite sure what the issue:

"I suppose it is possible your sensor is beginning to fail, but this is not the typical behavior we see with failing sensors.* *More commonly the level sensor would fail as a short circuit and blow the aftertreatment fuse.* When this fuse blows multiple fault codes are logged and the problem only goes away after the sensor and fuse are replaced.*

*I don’t have an explanation of why this would happen.** I would just recommend keeping an eye on it for a few days and if it happens again you may need to have it checked."



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Old 11-23-2022, 08:50 PM   #5
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def lite

I think i have noticed in the last month or 2 that the def guage wasnt very accurate to the amount of fluid in tank. When I take the head out i will ck it out thoroughly.
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Old 11-28-2022, 09:08 PM   #6
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def head

I received the new Def head today and it looks very different than the old one. The float is a black donut on the center pipe that just goes up and down and i dont see how that it could transmit level I dont see any type of electrical connection?
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Old 11-28-2022, 09:42 PM   #7
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I received the new Def head today and it looks very different than the old one. The float is a black donut on the center pipe that just goes up and down and i dont see how that it could transmit level I dont see any type of electrical connection?

Magnet in the "donut" and Hall Effect sensors in the center tube.
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