Electric mystery

[Will Hansen]

Our coach is parked beside our home, plugged into 50 amps, with refrigerator and all lights and devices off. Yesterday I unlocked the bay doors using the keypad. The locks sounded quieter than usual but did unlock. Last night I tried to use the keypad to lock the coach back up, but it was dead. I opened the door and the step deployed very slowly. I checked the battery voltage on the control panel and it said “float charging... 13.2v”. I shut off the shore power to the coach at the breaker in the garage (it had NOT tripped) and returned to the coach. Now the panel read “DC voltage 12.9v”. Hmmm.... That’s 100% charged in my book. As I exited the coach, I noticed a little red battery icon was illuminated on the Valid air leveling control panel. And the door lock keypad was still dead. So the coach was behaving like the house batteries were very low, but the batteries were showing good voltage.

I checked the water levels in the batteries (all good) and went off to think it over for an hour. Returning to the coach, the panel read “DC voltage 12.7v”. So still nearly 100%. So, as an experiment, I flipped the breaker to reconnect to shore power. The panel now read “Absorb charging... 14.3v”. So now it seemed to be charging normally, as if the batteries were low. The little icon on the valid panel was now gone.  The door keypad, and step retraction were now both working normally.

This morning all seems normal and panel reads “Float charging... 13.6v”.

So, my coach batteries are 4.5 years old and I can accept that they need replacing, but how come, if they somehow went dead while plugged into shore power did they show decent voltages through out this little fire drill? Is the problem in my charger? Nothing that I can see suggests that I’ve got a problem with the Big Boy.

Anybody know what’s happening?

Confused (as usual)
-Will

[David T. Richelderfer]

What charge status were the chassis batteries showing?

[Will Hansen]

I never checked the chassis batteries. Are you suggesting the Valid and door locks and step are powered by the chassis batteries? That would explain the symptoms but is that likely? For the record, they are AGM sealed, same age as house batteries. I don’t know how to check them other than trying to start the coach and I didn’t try at the time.
-Will

[David T. Richelderfer]

Someplace something wasn't right until you flipped the house breaker OFF and back ON.  It could be that flipping that breaker performed a reset on whatever was not working right.  I am not familiar with your electronics; our coach is a 2004 with an Aladdin, Silverleaf, etc.  I can easily check both battery banks for their charge status.  I am wondering if the inverter was "stuck" or the charging function (Big Boy/BIRD or Echo Charger) between the house and chassis batteries was "stuck" before the breaker was flipped.

[Will Hansen]

Yes, that’s what I’m thinking too. And, after I pushed ‘post’ I remembered I can check my chassis batteries via Aladdin so will do that if this situation reoccurs.

[Scott Shearer]

Will,

I’d suspect that your chassis batteries are not charging from shore power. I would be suspicious that your Big Boy relay is malfunctioning and needs cleaning. There’s a good chance that when you ‘cycled’ the shore power the Big Boy relay reset and made contact. On our coach, the air leveling and entry steps are powered from the chassis batteries, the keypad is not. You could verify the power source by turning the chassis battery disconnect switch off.

It is not uncommon for the charger/inverter to increase a charge level when the shore power is removed and restored.

If you use the Aladdin system to check the chassis battery voltage, don’t start the engine, just turn the key to on. If you start the engine the alternator will start charging and you will not be able to tell if the chassis batteries are charging from shore power.

[Steve Huber Co-Admin]

Will,
The keypad on your coach is also powered by the chassis batteries. Scott's analysis is correct that the chassis batteries weren't at full charge and  that the Big Boy solenoid is the most likely culprit. In addition to using the Aladdin, you can also use a meter to check the voltage at the Big Boy terminals (large ones). If the solenoid is engaged (one of the battery sets is at 13v), you should have the same voltage on both terminals. If not, check to see that you have ~4v on one of the small terminals on the solenoid. This is the latching voltage from the BIRD. If it is there, the Big Boy is not making contact and needs cleaning or replacement. I had this occur on mine once. I used the boost switch to force it to close a number of times which apparently cured the problem because when I subsequently disassembled it I found the contacts and washer clean. Reassembled and no more problems to date.
Steve

[Will Hansen]

Scott and Steve,
Earlier this morning I turned off the Shore power breaker and then flipped the chassis power switch to off. My keypad and Valid still had power (didn’t think to check the steps). They lost power when I then turned the house power switch to off.
 
So that’s kind of strange. I’ll test voltages as you suggest.

 I plan to check The chassis batteries via Aladdin without starting the engine if and when the problem reappears. I’ll study up on cleaning the Big Boy and may do that task In any case, but I’d like to see the problem reoccurring to incriminate something.
Thanks
-Will

[Will Hansen]

For the record, I can’t use the Aladdin to check the chassis batteries unless I turn the key to the right
, which starts the air heater, which sort of defeats the purpose, as the air heater is using significant power (I see 11.7v). Turning the key to the left (“accessories”) allows me to see the cameras, but all engine data, and battery voltage is “xxx”. Coach starts fine. Chassis voltage works it’s way up to 13.7v as alternator does it’s thing.

Assuming, door locks and Valid are on chassis batteries and a glitch in the Big Boy is the Original problem and I managed to reset it, the mystery has now mutated into “why does the keypad and Valid stay on when chassis power is turn off?”   
-Will

[Mike Shumack]

If you are shutting of power using the "Coach Power" switch at the entry door - rather than the Battery Disconnect switch (at the rear), then I think it is normal (and desired) for the Valid and Keypad to stay powered up. Also you want the security system and Co detector to stay powered up. If you want everything off (say for storing Coach) then you use the Battery disconnect at the rear of coach.

The Coach Power switch (a.k.a. Salesman's switch) only shuts off a few 12V things in the Coach, like the interior lights. So the Coach Power switch at the entry door is used when you just want to quickly leave the Coach but don't want to run around inside turning off or checking lights in the bedroom or closet or such.

[Steve Huber Co-Admin]

Will,
What I think is happening is that the Big Boy remains closed when one of the the battery switches is off, if the other battery bank is at ~13V.  The BIRD keeps the Big Boy closed for about a minute+ after it senses one of the banks is below 12.5 V. This allows that battery bank that is still on (house in your case) to supply the front PCB via the chassis battery connection. In other words, if either battery switch is on, the front PCB will still receive power via (in your case) the chassis battery line. Both switches must be off or the Big Boy needs to be open to deprive the front PCB of power. To better understand this look at the High Current, Low Voltage diagram in Coach Assist (07+ Contessa Wiring Diagrams).  Thus, I think Scott's and my guidance remains correct regarding the Big Boy not closing, allowing the chassis batteries to run down.

BTW, this is why I highly recommend using a meter to verify a lack of voltage when working on DC elec issues, rather than simply relying on the battery switches.
Steve

[Will Hansen]

Mike,
I was using the battery disconnect switches at the rear of the coach for my tests. The salesman’s switch Is a grandchild magnet that should never have been invented.

Steve,
Thanks. I think that’s the answer. On a different topic, I‘m wrapping up work a .pdf covering my airbag replacement fun and games. What would be the best email address To submit for the library? Lots of pictures embedded so the file will be a few mb.
-Will

[Steve Huber Co-Admin]

Will,
Click on my name/photo when logged in and you'll see my email in my profile. Will PM it also.
Steve

[Scott Shearer]

I second Steve’s comment about using a meter to check for the presence of DC power. The battery disconnects kill most, but not all DC power.

The ECU is always powered from the chassis batteries.

There is an ‘always hot’ circuit from the house batteries that feed the various 12-volt detectors (CO & Propane) and backup power for other items. With our coach, there is 12-volt high-amp (battery level) power present in both the front and rear run boxes even with the house disconnect off.

The only way to ensure that all DC power is removed is to disconnect the batteries. If you have two sets of house batteries, you need to disconnect both sets. I would recommend disconnecting both + & -, as they can back feed through the ground for the solar system.

And don’t forget the solar system, it can supply power with the disconnects off.