[Dennis4809]

Take pictures so you can be sure to hook them up the same way. Don’t know your rig but since three batteries, one that checks good and 2 bad, does that mean that you have a gasser with a single chassis battery and two batteries for the house? If so, you’d only need to replace the 2. Since they are 12 volt batteries, they will be in parallel so positive to positive and negative to negative.