Troubleshooting 1988 Mallard Motorhome with 3 Batteries

Question:

1988 mallard I have 3 batteries in my rv and sometimes my trailer is completely out including the emergency starter and I use the jumper cable on the middle battery to jump start the trailer. Now, I cant even start the trailer. I charge the middle battery but it wont start. The generator still works but it takes a long time to start up. The previous owner told me the left battery when facing the trailer is for starting up the rv. I took the left battery to Autozone and they checked it and fully charged it but it still wont start up my rv. Can you pls help. Im in the military and this is my home. They have finally gave me a spot to move to from the overflow and now I cant even start up my trailer. Thank you for help

asked by: Penn

Expert Reply:

To be of assistance because you have 3 batteries, I will need to know how they are wired. I assume you have one battery for a vehicle start battery and then two house batteries wired in parallel. This is the most common way 3 batteries are connected in motorhomes.

It sounds like your primary start battery is being drained by your other batteries, so even when it is fully charged as soon as you connect it, it loses amperage because of the draw from the other batteries that need to be charged. I recommend using a solenoid between the starting battery and your house batteries like # TR118665 which will isolate the house batteries from drawing power from the start battery when the motorhome is not running so you can start it in the future without it being depleted by the other batteries.

To solve your current problem, I recommend disconnecting your house batteries and having them checked out. Ideally you want your house batteries to be deep cycle batteries so they will have more amp hours of use before depleting. Even with your house batteries removed, as long as your primary battery is charged, you should be able to start your engine. If you cannot, it is most likely a starter issue or if it starts and then quickly loses power and stalls then an alternator issue.

You should be able to jump start your motor to get you moved unless there is a mechanical issue.

expert reply by: Jason S