Truck Battery discharging overnight

[mharrel]

Hoping you guys can help me. Ive got a 2013 class c Coachman on a Ford E450 super duty chassis.

The truck battery, alternator, volt reg have been checked professionally several times this last week at three different battery stores. The battery is dated at 11/17, so it is almost 4 years.

The truck battery will discharge overnight. It will go from the 12.7v to 8.0 or lower over night and the truck will not start in the morning. I have made sure to turn everything in the truck off (radio, cell phone cable, interior lights, key in correct position, etc) and it still does it. I can jump start truck and drive and battery charges ok. I can charge battery back to spec voltage and it will start and run.

While charging yesterday, we noticed a "ticking" sound coming from under the steering wheel area. Could not locate the source of sound. I could hear ticking sound, both if engine was running or off. I tried to pull one fuse at a time to see which circuit would stop the ticking but could not do all the fuses as some were too big for my puller to extract. I disconnected neg terminal and ticking stopped. I have left it disconnected and charged battery. It is holding voltage while disconnected.

So, Im confused. What is drawing down the truck power? This has only started in the last week. Previously, it has been very reliable and worked fine. If I charge the battery and disconnect from truck it will stay charged to spec voltage overnight.

Any thoughts or ideas would be greatly appreciated.

[enblethen]

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]

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

[trailrider]

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.