Seneca DEF residue burn off question.

[Dchafe]

We purchased our 2020 Seneca 37HJ a couple months back. There is a switch next to the exhaust brake switch on the dash. The PDI guy said you flip that switch to burn off DEF fluid residue “every once in a while”. Can someone elaborate what the technical name is? When do you flip it on? How often? Is it related to the engine or the generator or both? He couldn’t answer really what it does. He said it comes standard on the senecas and to read the owners Manuel on it. Couldn’t find it in the Manuel. Appreciate the advise!

[EA37TS]

That’s the regen switch. When excess soot builds up in the Diesel Particulate Filter (DPF) the regen increases exhaust temp to burn off the spot. If you run predominantly highway speeds you should need to worry about because the coach will regen while driving. A forced regen using the switch will take 30 to 40 minutes.

I’m not an expect and that’s how I under stand the regen process.

[Shokyle1]

Cannot say for sure on a freightliner but on the Peterbilts I work on the switch will only work if the dash says a regen is required. You need to be stopped with the engine running and hold the switch in the up position until the engine idle ramps up.

[Dchafe]

That was the question he couldn’t answer is when do I engage it? Does a light come on when it’s time to flip the switch? Can you regenerate when driving down the road? Does it turn off when finished ? He simply didn’t know. All he said is he thinks you turn it on every once in a while. So I thought what better place than to post on the forum.

[RVermont]

In 3 years I have never had to regenerate the system. As long as you dont idle your unit and drive it the unit should self burn as the engine heats the exhaust. Deisel engines used to require idling before and after running but the units dont require this and it can cause build up that will require the high heat to burn off. A few minutes before and after driving is plenty of idle time. I have only seen the regen light come on while sitting in rush hour traffic around washington dc but I never got to the point of actually having to use it.

If you ever have to do it the system heats the exhaust to approx 1000 degrees f. So it is best to park on gravel or concrete not on grass or blacktop as it can start fires or melt the blacktop. The cummins manual explains the process fairly well if you want to understand the process further.

[McGintys924]

Everything that has been said is what I knew. Once, after driving on some back country roads, it asked for a regen but I knew I was coming to a HWY soon and once I got up to speed it took care of itself.

Don’t know if anyone else experiences this but on occasion, after idling, the engine will pick up its RPMs for about 10 min and then idle back down; i don’t know what it’s doing there. Always wondered if it was a regen.

[Dchafe]

As always, thanks for the replies. I wasn’t getting a clear response from the dealer so knew the question would get answered here.

[EA37TS]

Originally Posted by Dchafe

As always, thanks for the replies. I wasn’t getting a clear response from the dealer so knew the question would get answered here.

Could your dealer spell "RV"?

[Mark S]

I have just turned 29,000 miles and have never needed a regen.

[McGintys924]

And the burnt circle of grass In my yard where I pulled In last night demonstrates RVermonts point!

[Robbbyr]

The dash switch will start a parked regeneration, but ONLY if the emmisions control system feels it is required and flashes the dash light to inform the driver it is needed. Our units will likely never need a parked regeneration unless it is operated extensively in a stop and go environment or if it spends hours and hours idling. Most RVs are driven at highway speeds enough that system will automatically perform a passive regeneration.

Here is a document that may help explain the dash lights and how to do a parked regeneration should it be indicated.

[75462]

FYI, if you ever need to idle for long periods you should fast idle. Turn Spd/Cntl switch on then toggle Res/Acc switch = 1000 RPM idle.

[Bruceter]

Originally Posted by Robbbyr

The dash switch will start a parked regeneration, but ONLY if the emmisions control system feels it is required and flashes the dash light to inform the driver it is needed. Our units will likely never need a parked regeneration unless it is operated extensively in a stop and go environment or if it spends hours and hours idling. Most RVs are driven at highway speeds enough that system will automatically perform a passive regeneration.

Here is a document that may help explain the dash lights and how to do a parked regeneration should it be indicated.

Thanks for posting this document Rob. Much better descriptions than in the Cummins or Freightliner manuals.
On a recent trip we had stopped for lunch and had one of these lights come on, I couldn’t tell whether it was a “High Exhaust System Temp” lamp or a “ Aftertreatment DPF” lamp. By the time I had got my glasses on it had gone out, so I put the fast idle on for about 10 minutes and then shut it down for lunch. After lunch back on the highway and everything was fine.

[McGintys924]

Originally Posted by 75462

FYI, if you ever need to idle for long periods you should fast idle. Turn Spd/Cntl switch on then toggle Res/Acc switch = 1000 RPM idle.

From what I understand the prolonged idle allows the pistons to cool and shrink more than the cylinders and allows fuel into the oil; what are your thoughts?

[Dchafe]

Thanks Rob for the info! I am printing it as we speak!

[AaronL]

Originally Posted by McGintys924

Everything that has been said is what I knew. Once, after driving on some back country roads, it asked for a regen but I knew I was coming to a HWY soon and once I got up to speed it took care of itself.

Don’t know if anyone else experiences this but on occasion, after idling, the engine will pick up its RPMs for about 10 min and then idle back down; i don’t know what it’s doing there. Always wondered if it was a regen.

Mine did the same last week after some idling and before I took it out for a drive.

[GCAT9110]

I have on occasion used the idle-boost feature. It uses the cruise switches to bump and hold the idle in park to 1500rpm.

[rgolding]

At over 75,000 miles I've probably had it come on 3 times. Hold the Regen switch in for a slow count of ten. Release and shortly after that the warning on the dash will go out. Happens so seldom, its hard to remember what to do.

[75462]

Originally Posted by McGintys924

Everything that has been said is what I knew. Once, after driving on some back country roads, it asked for a regen but I knew I was coming to a HWY soon and once I got up to speed it took care of itself.

Don’t know if anyone else experiences this but on occasion, after idling, the engine will pick up its RPMs for about 10 min and then idle back down; i don’t know what it’s doing there. Always wondered if it was a regen.

Could be this!

Voltage-Based Auto High Idle
1. Place the shift lever in Neutral (N) or Park (P)
and set the parking brake.
2. The idle rpm will automatically increase when the
voltage drops below 12.2 volts. The rpm will incrementally
increase every five seconds until
13.4 volts is achieved and maintained.
3. The Voltage-Based Auto High Idle system is disengaged
by depressing the service brake pedal.
IMPORTANT: The Voltage-Based Auto High Idle
system will not return to normal operation until
one of the following occurs: The parking brake
is depressed and released, the key switch is
turned to the OFF position, or the transmission
gears are changed.

[32Pinnical]

In the Manuel for my F250 6.7 it states that the regin is to clean the DEF filter and it requires the engine to run at 1500rpm for Ten to fifteen minutes while up to five gallons of fuel is dumped into the exhaust system to increase the temperature to burn off deposits in the filters.