Electrical gremlins

[Mike Merchant]

Sandy and I took our 06 Monty to BCS for routine LOF in mid-Oct and ended up with an 09 Contessa Rome 42 with 425 Cat, 17,000mi. Running lights noted to flicker on delivery, thought to be moisture from detailing pressure wash. BCS transferred US GEAR brake controller from Monty to Contessa.May have had smartwheel relay installed for brighter headlights at that time also,but not certain.
Got home and noted MH tailghts flickering, tow had brake and turn signals but NO running lights.
Since have found chassis batteries dead at 24 hours if not on shorepower, brake lights fine if running lights are not on, if running lights on then tailights show as brakes on (both filaments) continually,one episode of leveling system alarming for right rear fault only to be all green the next time startedup, during recent drive the Cat DPF cycled with the dash HEST light on,smelled like burning rubber at right rear near exhaust.
Obviously will be heading back over the mountain with a weather window but any thoughts I can help Ken at BCS with will be appreciated.  

[Gerald Farris]

Mike,
The taillight/stoplight problem sounds like an open ground circuit. The rest of the problems would take some investigating, however they do not sound like they are related to a common problem.

Gerald

[Gil_Johnson]

The DPF cycling is normal, as is the high temperature warning (not alarm) when moving at less than 5mph.  The hot smell is also normal.  It the DPF is cycling when you stop it's really hot, I think 800 degrees plus.

If the coach hasn't been to CAT lately, you should get it in for a software update that takes care of a chronic low intake boost pressure alarm.  I believe it also changes the DPF cycling.  If you don't know, the C9S (EPA 2007+ engine) has created some challenges for CAT.  Many have been corrected.  The one that remains unresolved and CAT has said it's Monaco Coach's (not Monaco RV) is that the Air to air cooler or charge air cooler (one in the same) is undersized.  The low intake boost pressure alarm, that's been taken care of with the latest engine software, may be result of that undersizing.  Monaco RV has a replacement ATAC or CA available for purchase.  It's unclear to me if it's a direct bolt in replacement, but I doubt it.  Furthermore, due to CAT's reginal approach to managing issues, the east coast CAT service rep doesn't know what it takes to have the CAC changed out.  There has been one coach that had the replacement CAC installed somewhere on the west coast.  If anyone knows who this is, maybe they can share what was involved with the replacement.

[Mike Merchant]

Looks like you were right on, Gerald. My local RV guy who has been looking into this just called and found one of the brake light bulb filaments had broken then welded itself to the other creating somekind of brake light short circuit resulting in brake lights on when running lights were on.
He thinks the battery discharge thing may be due to a malfunctioning Big Boy switch since there is some buzzing sound coming from that unit. He is investigating further. Does this sound feasible?
Gil- am aware of the CAC controversy, wasn't aware there is a software update.Will have to pursue that later. We're in Olympia,Wa so maybe west coast is ahead of east coast on that one .

[Gil_Johnson]

Mike, unfortunately for me the west coast coach was used for the CAT retro fit before mine could be.  Mine was used to validate the problem, just not offered the fix   The CAC replacement is an owner expense.  This is one of the problems directly attributed to Monaco Coach going.  I don't blame Monaco RV, but blame is a whole another discussion.

Let me know if the Big Boy solenoid is a problem.  Mine too buzzes when it's energized.  Given it appears to disconnect when it should, I haven't given it much thought.  My batteries will drain with bthe both battery bank switches off, but it takes a couple weeks.  In my case, I know the charger/inverter controller is still engaged when the main cutoff switches are off, I don't know what else is also on.

[Gerald Farris]

The chassis batteries are still powering the ECM (engine control module) with the battery bank switches turned off. The parasitic drain of the ECM to maintain it's keep alive memory will kill a pair of chassis batteries in one to two weeks. This time will vary with engine models and battery condition, however it is a common problem with all computer controlled heavy duty diesel engines.

Gerald

[Edward Buker]

Based on what we learned from Cats review as to the background behind powering the ECM continually, it would be fine to add a manual switch to the wiring in the battery bay that services the ECM (probably would have to find it with a schematic or clamp on current probe) to disconnect the ECM during long term storage.

The main issue seemed to be the start up time was reduced given the ECM did not have to go through extra steps to reset itself due to having to go through a full power up cycle. For storage that should not be an issue, just turn the ECM switch and the main switch bank power back on in the bay and do not run to the cab...

For those that do not have a "plug in" at the storage facilities, this would probably extend your battery life due to the batteries not being deep discharged. It would also eliminate the pain in the butt of dead batteries when you cannot get back to the coach soon enough.

Later Ed

[Keith Oliver]

I learned what Ed is talking about the hard way.  I now have a positive cut-off, a knife switch, between the neg battery terminal and its cables.  My chassis batteries will now have zero load, for storage.  I also did this before I knew anything about the ECM, and had no effect on it whatsoever.  The starting sequence went just the same as it had before.  The only thing I had to do extra, was to reset the clock in the radio.  I will be storing for a couple of months again this winter, without a plug in, so will be using the knife switch again.
The coach batteries already have a "power off" switch, and apparently no parasitic loads.  At least, when I stored in March, they were still strong when I powered up again.

[Joel Weiss]

This discussion about keeping the ECM powered up leads me to ask what is probably a stupid question.  I'm planning on replacing my chassis batteries later this winter (just based on age) but I am wondering if there is a special procedure that should be followed.  We're going to be plugged in at a CG and I assumed it would be safer to disconnect the shore power, but do I need to do anything else?  Does it matter if the house batteries are connected or switched off? What is the effect of the ECM not having had power while I am swapping out the batteries?

[Edward Buker]

The ECM will be fine. You can cut power to that without any consequences. You would disconnect the AC to the inverter charger before you disconnect the house batteries but you do not need to do that for disconnecting the chassis batteries. I would pull the fuses for the Echo Charger if you had one, to disable that unit, and shut off the Chassis Battery switch to remove any load before disconnecting the batteries. If you have any doubts, make a little wiring diagram of the leads and where the +/- battery terminals are located. Basically two 12V batteries in parallel...

Later Ed