Coach batteries = house part of the rigChassis batteries = truck part of the rigThe step (despite being in the house) is run from the chassis battery. So the coach batteries being dead should have no impact on the step.If the coach batteries are really dead and the RV place isn't conning you, then 3 years is NOT a good working life of properly maintained and charged batteries. 8 to 10 years with good maintenance is more normal. However, poor charging, boiling them dry or running them down low and not recharging quickly can greatly reduce the life. Rule of thumb is to never discharge them more than 50% and to recharge as quickly as possible. That varies by type of battery somewhat but is a good guide.Do you have regular wet cells or AGM? If wet cells have you monitored the water level monthly? If the water gets too low it can ruin the batteries. If you run the batteries down completely dead you can ruin the batteries. In storage there is normally some small drain on the batteries even if the switch is in the storage position so long term storage can run them dead. A trickle charger is recommended to prevent this. Unless your PC is different and the step is actually hooked up to the coach batteries I think you might have two completely different problems. 1) An issue with the step, which might be a corroded step switch or loose wire. 2) An issue with the coach batteries which might have been caused by the items listed above.
Question: We picked up our brand new PC in October 2014, so the batteries are a little less than three years old. Is this the "normal" life for coach batteries? When our coach was not being used we always had the switch in the "storage" position. Our PC has 40,500 miles on the odometer. Question: Also, even when we were plugged into shore power at the KOA campground, the step didn't work, which I thought it would have worked. MB Sprinter chassis battery seems fine, never had any problems starting her up? Ron, do you think our chassis battery needs to be replaced also? Looks like we won't be able to get on the road until after labor day.Cindy Gentry