12 Volt Power Issues

I've been having 12 volt system issues with my Winne Adventurer 35U for a couple of months...here's what I know:

Chassis battery goes dead after sitting for just a few days.  Had to use Booster Switch to start engine.

Replaced chassis battery with new last weekend.

Coach battery tests good always.  Yesterday when I arrived, generater started, no problem.

Tried to start engine, had to use Booster Switch and everything went dead, generator stopped, no power to coach anywhere.

Jumped chassis battery with portable jump-starter, engine started and was able to start generator.

All 12 volt and 110 volt systems back online.

Could this be the Booster Switch solenoid gone bad?


Edit - changed message icon to topic solved

The job of the "boost" switch or battery mode solenoid is to bridge the chassis and house battery banks together when a) the engine is running or b) when you operate that switch.  I do not see how that solenoid could cause your symptoms of suddenly loosing power.

If you don't have a Trik-L-Start or Xantrex Echo~Charge installed, then your chassis batteries are not being charged while on shore power - you should install one of these asap.  There's a Tech Tip write-up on the Winnie website detailing how to install.

What I would do:

- check all of your battery connections, positive and negative
- measure your parasitic load on the chassis battery (most inexpensive multimeters will measure to 5 or 10 amps, plenty for this need)
- install the Trik-L-Start (or equivalent)

Hi John,

I can always count on you to offer your help here on the RV Forum Community.....THANKS.

I don't have the ability to be on shore power where my RV is stored.  I will definitely check to see if I have some kind of parasitic draw on the chassis battery.

My question is:  If the chassis battery is completely dead...0.00 volts, and my coach battery shows 12.4 volts, why don't I have 12 volt power to the coach?  I checked my battery disconnect switch at the steps, but it doesn't activate the solenoid.

As soon as I installed the new chassis battery, everything came back to life....however after only 48 hours the chassis battery was dead again, then I jumped it to start the engine, and everything came back to life again.

The mechanic at the RV center suspects the battery boost solenoid is bad.

"...Coach battery tests good always.  Yesterday when I arrived, generater started, no problem.
Tried to start engine, had to use Booster Switch and everything went dead, generator stopped, no power to coach anywhere..."

There are a couple of things that puzzle me in here, and perhaps someone could explain. Firstly I had the sense that the generator started off the chassis battery, no?  Secondly why would the use of the booster switch cause 'everything to go dead' (coach 12 volt system/battery and generator). I think he has at least one issue in here beyond a phantom load on the chassis.

You have three electrical systems in your motorhome. There are no mysterious elements to it, but it is very difficult to troubleshoot three interrelated systems without understanding those systems, electricity, batteries, and battery charging.

I don't advocate the hit and miss approaches, but it does take a lot of time to learn about the above 4 items.

Meanwhile, since you are focused on the solenoid, pull it and bench test it. Then keep guessing and good luck.

A good technician and owners will use their list of what most likely went wrong in these situations based on their past experiences and knowledge to hopefully get the issue resolved quickly. Then, if he is skilled enough, he will shift to a systemized troubleshooting approach or lacking that get another tech to help or the owner pull some $$$ out of his pocket for a good technician.

I had a tech that wasted a couple of hours doing trial and error replacements on a kwikee step. His electrical background was poor and also his reading skills, never being willing to look at a kwikee manual, not having a testing pigtail in his kit or following the kwikee troubleshooting process. If he had been able to and willing to do so, he would have determined within 30 min that all of the mechanical items worked and that all he had to do was clean and tighten a loose ground wire.

The fact that the momentary "Boost" switch activates the solenoid, leads me to believe that the batttery isolation solenoid is fine. The generator does start off the house batteries and not the chassis battery.

The first thing I would do is check and clean all of the battery ground connections and especially the frame grounding bolt.

What chassis do you have? It's possible there is a bad diode in the alternator.

John Hilley said:

The fact that the momentary "Boost" switch activates the solenoid, leads me to believe that the batttery isolation solenoid is fine. The generator does start off the house batteries and not the chassis battery.

The first thing I would do is check and clean all of the battery ground connections and especially the frame grounding bolt.

What chassis do you have? It's possible there is a bad diode in the alternator.

Click to expand...

Hello John,

Battery terminals were cleaned a couple of days ago.  My Adventurer is on an F53 chassis.  The alternator is putting out charge voltage with engine at idle.  There seems to be a parasitic current draining my chassis battery.  That is my next step to try and find the culprit, or maybe even put a battery disconnect switch on the chassis battery.

With a bad diode, the alternator can still charge, but will discharge the battery while not running.

PAHipskind said:

"...Coach battery tests good always.  Yesterday when I arrived, generater started, no problem.
Tried to start engine, had to use Booster Switch and everything went dead, generator stopped, no power to coach anywhere..."

There are a couple of things that puzzle me in here, and perhaps someone could explain. Firstly I had the sense that the generator started off the chassis battery, no?  Secondly why would the use of the booster switch cause 'everything to go dead' (coach 12 volt system/battery and generator). I think he has at least one issue in here beyond a phantom load on the chassis.

Click to expand...

The only way I can see this happening is if the chassis battery(ies) were completely discharged, with the two banks bridged together the house bank would discharge into the chassis bank pulling the voltage way, way down.

John Hilley said:

With a bad diode, the alternator can still charge, but will discharge the battery while not running.

Click to expand...

I checked the chassis battery with the ignition off and there is a 2 amp continuous discharge.  Would the diode on the alternator draw that much?

John Canfield said:

The only way I can see this happening is if the chassis battery(ies) were completely discharged, with the two banks bridged together the house bank would discharge into the chassis bank pulling the voltage way, way down.

Click to expand...

I DO believe that's what's happening.  I have to find out what that 2 amp parasitic discharge is.

A diode doesn't "draw" anything. It is merely an electrical one-way valve (check valve). The diode in the alternator basically converts it from an alternating current device to direct current. The only "draw" in an alternator is the "exciter" current which is used to initiate and then regulate the charging output. It is insignificant.

Gary RV Roamer said:

A diode doesn't "draw" anything. It is merely an electrical one-way valve (check valve). The diode in the alternator basically converts it from an alternating current device to direct current. The only "draw" in an alternator is the "exciter" current which is used to initiate and then regulate the charging output. It is insignificant.

Click to expand...

It's a new one on me, but apparently John Hilly is familiar with a scenario where a blown alternator diode can cause a discharge, I'm assuming the diode would have to failed in a shorted condition.

Back to Brett's situation ...

Two amps is quite a bit of parasitic current - I think you should be 200-500 ma at the most.  A fairly common culprit for chassis battery drain is the Kwikee steps - unplug them and see if that's the problem.  Just to rule out a long-shot with the alternator, disconnect it as well.

Here is a YouTube video showing a 2 amp parasitic draw from a bad diode in the alternator

https://www.youtube.com/watch?v=2x0o4-bNCvY

John Canfield said:

.....
Back to Brett's situation ...

Two amps is quite a bit of parasitic current - I think you should be 200-500 ma at the most.  A fairly common culprit for chassis battery drain is the Kwikee steps - unplug them and see if that's the problem.  Just to rule out a long-shot with the alternator, disconnect it as well.

Click to expand...

The parasitic culprit was found.  Back a few months ago, my RV was burglarized and the dash radio and backup monitor was ripped out by the wires.  After the RV Center replaced the radio/backup monitor, they discovered that the wiring from the dash airconditioning was shorted out from all the wires being ripped out.  After repairs to all the dash air wiring, including replacing the compressor that also got shorted out, there is a 2 amp current in the wire that feeds the dash air relay even when the ignition switch is off.  Quick fix for now, installed an ON/Off switch on that wire to eliminate draining the battery when parked.  Will try and troubleshoot that circuit when we get back from our trip to Savannah, GA.

Ah, the mystery is solved - good troubleshooting!  Thanks for checking in with the resolution.

Holy cow! Impressive detective work.  I must say that I've found this thread exceptionally educational. Thanks for posting this out there!

John Canfield said:

Ah, the mystery is solved - good troubleshooting!  Thanks for checking in with the resolution.

Click to expand...

Additional Info:

The A/C relay is located in the fuse box under the hood on the firewall.  Not sure why yet, but the On/Off switch works.

They probably just wired it to the wrong power source. There are normally 3 distinct power terminals available for dash use:

(1) Always on (battery direct)
(2) Accessory (key in Accessory position)
(3) Ignition On (key On)

Some may have a 4th, which is key on  and engine running, meaning power only when the alternator is actively producing power.

Gary RV Roamer said:

They probably just wired it to the wrong power source. There are normally 3 distinct power terminals available for dash use:

(1) Always on (battery direct)
(2) Accessory (key in Accessory position)
(3) Ignition On (key On)

Some may have a 4th, which is key on  and engine running, meaning power only when the alternator is actively producing power.

Click to expand...

Thanks Gary,  I'm going to look into this.