We have a 2021 Coachmen motorhome on a 2021 E450 cutaway chassis. I'm hoping some E-Guru will read this and say "I know exactly what's going on!". If it sits for more than a few weeks, the chassis battery will go dead. As I inquire around, this seems to have become a common issue with current Class C motorhomes on E-450 chassis. Most people get around it by doing a permanent install of a 110 volt Battery Tender to maintain the charge (as long as the RV can be kept plugged in). Earlier coaches had a disconnect switch for both the coach and chassis batteries but for some years now, the chassis battery has been left to it's own devices. I recently installed a blade type cutoff switch on the negative terminal to stop the discharge from happening. I know I can now put a meter across the terminals of the open switch and start pulling fuses one at a time until the voltage reading goes away (This scheme will work as long as it's only ONE "phantom" draw). Before I get into pulling the myriad of fuses, however, what I have noticed is that if the switch is left open for a couple hours, when it is closed again I hear what sounds to be some sort of little motor starting up underneath the air cleaner box then stalling out as though it moved something up against a stop. Would that just maybe be a blower door moving around? As it looks to be a not small job to pull all that stuff off, I'm hoping someone can enlighten me as to exactly what that is and if me unhooking the battery every time we park the rig is not such a good idea. TIA!

 

Shouldn’t a year old RV be under warranty?

Our ‘93 E150 had loose visor mirror covers. If we left the visors against the windshield, the covers would droop enough to illuminate the vanity lights but not enough that we could see the vanity lights on from outside.

I read that bad alternator diodes can cause battery drain.

Sixto
07 E350 5.4 180K miles

 

It is still under the 3 year B to B warranty but....... Only a select few Ford dealers will work on what they consider "heavy trucks" which includes the E350/450 Class Cs and the F53 Class A chassis. We are in the Reno NV area and the closest Ford dealer that does that is in Central CA about 200 miles away. The drill is you make an appointment, drop the vehicle off, then wait for them to call you again for pickup. This is a totally broken system that, unless something is VERY major, it makes far more sense to just fix it yourself making the warranty mostly worthless as, if you do the required maintenance, the likelihood of a modern Ford truck having any big mechanical issue during the warranty period is slim to none. Particularly with gas prices being what they are, making multiple 400 mile round trips is a non starter. As it takes weeks for this issue to happen, it has to be a pretty tiny draw. The disconnect switch makes this a back burner issue for me for the time being. If I'm lucky, I'll stumble across someone who already went down this road and has a pretty good idea of what it is!

 

Failing alternator diodes can indeed cause a huge parasitic draw that can drain even a large capacity battery quite quickly. Any competent auto electric shop can diagnose this condition.

With these Motorhomes problems like this can be caused by the chassis components or the bits and pieces the "home" builder installs.

 

As I alluded to in my other posts, the draw is quite small, taking weeks to do it's dirty work. Also, this seems to be VERY common with many newer Class C owners with the E-chassis complaining about the same thing, most just adding a trickle charger to get around it. Interestingly, the Class A F53 chassis motorhomes don't seem to suffer the same problem and can set for a much longer time without the battery going down. Older RVs almost always had two disconnect switches, one for house batteries, one for coach but I guess the advent of so much computer stuff that is always on has caused the removal of the chassis battery switch. I'll just have to go to work with my milli-ammeter and try to determine which module/circuit is the culprit. If I can determine what is causing the issue, my next idea is to rather than the big battery cutoff switch, break that individual guilty circuit with a small relay that will be energized when the ignition switch is turned on. That way if it doesn't turn out to actually be the radio doing it, at least I won't be losing my presets every time I open an "everything" disconnect switch. Another thought is, if it is NOT the radio and I keep the battery disconnect, break out the radio's "always on" feed and run it through a fuse to the hot side of my new disconnect switch to preserve the presets. Another change is the manufacturers have quit providing an "Emergency Start" button on the newer Class Cs. This energized a relay that connects both the house and chassis batteries to let you jump start the engine with the house batteries if the chassis one goes dead. I have seen nothing on paper but the rumor is that was done at the request of Mercedes Benz who said they would not continue warranty coverage if the feature was present. Apparently the RV builders just applied that logic across all models for consistency. At least on Ford RVs that circuit and relay still exists but only energizes when the engine starts to tie the batteries together so the alternator can charge them all.

 

3 weeks?
The spec is 14 days for normal parasitic drain and your vehicle will not start
If you have a brand new battery and a battery saver relay it may last 3 weeks several times and then drain the battery
A new battery is only good for about 5 complete drain cycles before being no good
Good luck at the dealer or other shop which will most likely find no problems
One of them may sell you a battery or a new alternator even but 3 weeks later your battery will be dead again
If your battery goes dead overnight then you would look at the alternator
Good luck drive the van once in a while or get a battery tender

 

I guess your reply is the one I have been waiting for. If 14 days is now considered "normal" for a battery to go down from all the assorted "always on" draws if you are not regularly starting, I guess there is likely no "problem" for me solve. The problem with RVs is they often live at storage lots where frequent starting might be problematic. This is never an issue when we are using our camper since we don't set somewhere long enough for the battery to go down. I suppose I'll just stay with my knife-blade disconnect solution to keep from wrecking the battery. As I store it at home, I could add a battery tender but since I always turn off the coach batteries anyway, a second disconnect might as well be used, too. Thanks, you've saved me from a lot of what would likely be fruitless searching for a non-existent issue.

 

This might be available in industrial size for your RV - https://www.prioritystart.com

Sixto
07 E350 5.4 180K miles