Breakdowns are the part of RVing that most of us would just soon forget.  These marvelous wonders of modern engineering provide such joy when they take us on journeys to outstanding places.  But, these mechanical beasts can bring us frustration, delays, and budget busting expenses when a problem occurs miles from home.

For most of us, breakdowns don’t happen that often but they do happen to all of us.  As a way of turning these negatives into positives, I figured I’d start to share my experiences with RV problems.  Luckily, I don’t have a plethora of them.  And, I’m not trying to be a how-to-expert or be a source of technical information, but rather just an RV breakdown “victim” venting about and sharing the experience.

Prologue

My latest problem appeared to be with the DEF system on the engine of the motorhome.  DEF stands for Diesel Exhaust Fluid.  Its a mixture of water and urea that is used to treat exhaust from diesel engines. All diesel engines built after 2010 use DEF to remove nitrogen oxide (NOX) emissions.  Its a consumable that is sprayed into the engine exhaust before it leaves the tail pipe.

The new diesel exhaust systems are super sophisticated.  On my rig, there’s a computer control unit just for the exhaust system that controls the DEF tank, monitors 7 different sensors in the exhaust system, a heater, and pump, and dosing valve.  All the exhaust data is fed back to the main vehicle control unit.  If it detects something out of range, the Check Engine Light will come on.  Too much nitrous oxide comes out the tail pipe – Check Engine Light.  Too much oxygen or not enough – Check Engine Light.  Too much fuel pressure or not enough – Check Engine Light.  Any sensor starts acting wacky – Check Engine Light.  You’re 500 miles away from the nearest service dealer having too good of a time – Check Engine Light (just kidding).  If you’ve got a newer diesel engine, get used to seeing the Check Engine Light.  Its a warning indicator that something may not be working quite right.

All this is in place not to protect the vehicle or the engine – its mostly to protect the Environment!  And gone are the days when you could ignore or reset this with an inexpensive Scan Gauge tool.  Sometimes, if the on board computer sees that the fault is corrected after a few restarts, it will reset the alarm itself.  But, many times the alarms have to be addressed (usually by  the dealer) or the vehicle will eventually go into Limp Home Mode after so many miles or restarts and you’ll be paralyzed by the dashboard light!

The Main Event

My latest experience was on the start of a trip to the Maryland seashore.  I had planned a week long trip to Assateauge Island.  I had made several reservations months in advance and my wife and I were really looking forward to a beach side vacation.  We took off on a Wednesday morning and got about 180 miles home when I noticed on the dashboard the yellow Check Engine Light was on and the low DEF alarm was on.  Damn!

Whenever I see a dashboard light alarm pop on in the RV, my stomach goes into knots.  I’m not sure why.  Perhaps its because I’m so focused on the trip and the adventure that when an alarm goes off its an unexpected jolt.  Like getting a bee sting.  But, this time I knew what this one meant so its wasn’t a total panic.  I had a similar experience this past June when I was on a trip out west (see Dealing with the Unexpected).

Since that episode in June, I have been religious in keeping the DEF tank topped off every 500 miles.  When I saw the lights this time I stopped and immediately topped off the DEF tank.  It only took about a quart to fill up the 3.2 gal tank and these alarms are not suppose to go off until the tank is down to its last gallon.  So, what to do.  My seasoned problem solving skills, honed by 30 years of solving major computer problems, kicked on. The RV was running and driving fine.  All I had was a couple of lights on.  I was in southern Connecticut, a pretty upscale area, so I thought to check on my smartphone to see where the nearest Mercedes Benz dealer was.  Bingo!!  I lucked out – there was one 3.2 miles down the road from where I had stopped!!!

Going to the Dealer

We got there and I described my problem to the service manager.  This is the fourth MB service dealer I’ve been to since I’ve had my Winnebago and they have all been super accommodating.  Al, the service manager, quizzed me about when I last topped of the DEF, how I filled it, and how old was the DEF that I used.

I think Al was quizzing me to see I’d confess to causing my own problem.   But, I gave him all the right answers and more technical info, exact mileages, and dates than he’s used to.  And I remained super nice answering all his questions because I didn’t have an appointment and I wanted him to look and my vehicle right away.

They did a great job taking me right in and had it in the shop for 2 hrs.  I figured this was good thing – they may actually be fixing or replacing something.  But after 2 hours, Al comes out and says “Ok, I’ve got some information”.  They confirmed that my DEF tank is full but the tank sensor is saying its empty.  Every time they reset the alarm it comes right back on.

Ok, this is good because it shows I have a hard failure.  But, its bad because, 1) Al doesn’t have any of the parts to fix it, 2) the sensor is built into the workings of the tank and he’s not sure which component within the tank to order, and 3) he’s not sure when he could get the parts.

I ask the way too obvious question – “Could you call Mercedes Benz tech support and ask them where the part is located and when they can have it to you?”  Al just shrugs and says he could but it’s late in the day and he’s not sure when they’d get back to him.  It was late in the day and I figured Al probably wanted to go home and not deal with this today.

I guess I didn’t want to deal with it either.  My RV was still very drive able.  It ran fine but I only had 10 restarts left before it would go into limp home mode (limited speed). We could easily make it back home in about 3 hrs with plenty of restarts to spare.  So, my wife and I quickly made the decision to cancel our trip, drive home, and have our local dealer fix the problem.  We thanked Al for his help.  Our trip was interrupted, but hey, shit happens.  Assateague Island will still be there next week, next month, and next year.

Epilogue

The RV ran fine all the way home and we had plenty of restarts to spare.  I had to wait a week for an appointment at my dealer but they ended up finding a bad NOX sensor that needed replacing.  Why does a NOX sensor go bad after only 17,000 miles and cause a low DEF alarm?  The MB tech had no answer.  But the good news is that they had it fixed the same day.  The cost to replace a NOX sensor is $700 but my Winnebago is still under warranty so the total cost to me was $0. Priceless!

And, the dashboard lights were out.  Non were glowing like the metal on the edge of a knife.  I can now see paradise without a dashboard light.  It never felt so good, it never felt so right.