auxiliary battery
I hve recently been told I should have replaced the auxiliary battery
when I replaced the engine battery. I am having issues with the main battery
not staying charged. should I replace both now? Its been 1.5years. Also
what sort of things are the auxiliary battery responcible for. I can not find a list in the owners manual.

I haven't come across that question before but we have a forum here that can address that. Click on the Forums tab at the upper left and look over the boards. I suggest trying this one: https://www.ford-trucks.com/forums/forum128/ There is also an electrical forum but I would try the one I listed first.
Stop by the Michigan chapter, here's a link: https://www.ford-trucks.com/forums/forum85/
Good Luck!





