Truck Battery discharging overnight

From The Internet:

A malfunctioning diode in the alternator can create a parasitic drain on a car's battery. Diodes should allow current to pass in only one direction, but a bad diode will keep the charging circuit open even when the engine in not running, allowing the battery to go dead. This often happens overnight.

thanks trailrider.
so the fix is to r&r the alternator? or can it be checked while on board?

You are talking chassis under your class C motor home?
In that case there is other items.
Do you have electric step? It has some draw.
Carbon dioxide detector, has draw from chassis battery
Charge relay from battery control center could be holding in so you are using power from chassis battery.
Yes, a diode in alternator. It should show up on a proper alternator test.
To test your self, disconnect and insulate the large wire on alternator. If battery stays up, replace alternator.

mharrel wrote:
thanks trailrider.
so the fix is to r&r the alternator? or can it be checked while on board?

If it was the alternator, I doubt you would here a ticking sound coming from under the dash.. Diodes generally when they go bad, short or open, ticking sound would not come from that.

Ticking would mean something like a motor running or a relay opening and closing.

2013 Fords often had wiring harness issues, one real bad one is there is a harness on the driver side which has a connector that the pins get damaged from the vibration caused by applying and releasing your parking brake. Ford decided it was a good idea to solidly wire tie one side of the connector directly to the parking brake assy.. The fix to prevent damage to the connector was to remove the wire tie and tie the connector and cable to another wire harness above the brake assy..

One other wiring harness issue has been moisture getting into several of the wire harness connectors at the rear of the vehicle.. On trucks those connectors are above the spare tire..

It will be difficult to isolate where the drain is coming from, so many over the top complex computerized systems and some fuses are in and around the engine compartment along with inside the cabin..

Starting off

Yank the cruise control fuse
Yank the windshield wiper stalk fuse
Yank the main Accessory fuse

e.nblethen :
thanks for the help.
yes, it's the chasis (truck) battery not the house battery.
no, no electric stairs

is the carbon dioxide monitor able to disconnect from power to check to see if that is problem?

would the "charge relay" be in the fuse box. it looked like there were a bunch of relays in there.

thanks for your ideas.

Sort of a fix.
Get a Battery Disconnect Switch, and put it on the engine battery, open it when engine is not being run.

mharrel wrote:
e.nblethen :
thanks for the help.
yes, it's the chasis (truck) battery not the house battery.
no, no electric stairs

is the carbon dioxide monitor able to disconnect from power to check to see if that is problem?

would the "charge relay" be in the fuse box. it looked like there were a bunch of relays in there.

thanks for your ideas.

Carbon monoxide/LP gas monitor should be only connected to the "house" battery, not the chassis battery.

If you are talking "charge relay" as the relay to charge your house batteries while driving, that relay would be mounted in the engine compartment not under the dash.

As far as engine charging goes, no relays involved, alternator is directly connected to the batteries as pretty much a industry standard. The diodes in the alternator prevent the alternator from draining the vehicle battery when engine is off.

What you are looking for is items which may have power all the time regardless of engine on or engine off.

in 2013, very few items are directly turned on/off via the keyswitch. Instead many items use Fords "CAN Bus" which is Fords version of a data network.

Good example of this is the factory stereo in that yr, the main connector to the radio does not have any ignition "switched" 12V power. Instead, the radio is turned on/off through the CAN bus data network, the radio gets data from the CAN Bus that tells it to power up or turn off.

The downside to this setup is all it takes is one broken or shorted wire anywhere on the CAN bus network to create a failure of the entire network which may cause modules using the CAN bus to not turn on or off when they are supposed to.

It is that reason why I mentioned the harness connectors at the rear of your vehicle, water intrusion damage is very real on 2011 and up Ford vehicles. One wouldn't think a little water in a connector that far away could cause things to not work correctly, but it does.

It is also the reason I mentioned checking the connector which is attached to the parking brake assy.. The pins break from the wire in that harness connector causing lots of electrical gremlins.

Does it tick about twice a second? My 2011 F150 did that while the ignition was on but not off. My ticking came from the AC blend door motor trying to find its home location. The nylon gear was shot so the motor constantly ran.

Your ticking may be something different.

Additional thought..

A "self resetting" breaker can cause a "ticking" type of sound as it will break connection on overload then after the breaker cools down will reset back to normal closed automatically. A short on one of those types of breakers can cause a ticking sound but generally it will take a minute or more so the click would be very slow.. Sometimes auto reset breakers would be used for things like headlights where a fuse might not be a good idea since a fuse would leave you stranded in the dark with no headlights.

Charge lines between vehicle and house batteries are a possible application for a auto reset breaker although Ford does use a relay and fuse on charge lines on their trucks, not sure about E series..