1985 holiday Rambler Kohler 7cm21

I sent you a PM on how I did it same generator.

As mr wizard said.

But yes an electrician can find the wiring and do a break out to a box with An extension cord so you power the rear unit, or maybe install the selector switch if you don't have one
My advice get an electrician and show him this post
Do not try this your self

I think you mean with generator you could power either a,/c unit
And on shore power only the front a/c works
And your generator has quit working
And you want to power the rear A/C

And that comment about whether plugged in or not
Makes me think you used to start the generator to power the rear a/c while still be plugged into shore power,
If true, could be what killed your generator

Some RVs came with a switch that would let you choose to power the rear or front a/c
It might be in the closet, or in the electric Bay
But yes an electrician can find the wiring and do a break out to a box with An extension cord so you power the rear unit, or maybe install the selector switch if you don't have one
My advice get an electrician and show him this post
Do not try this your self

You should have started your post
With i have two a/c unit, but the rear only works on generator and the generator died
That much more clear

With mine you have to take the 50 amp plug out of the wall that it is plugged into ( generator ) and plug it into the cable that feeds the motor home.

Thank you for responding! The HR transferswitch is the shore power or generator being plugged in. When the generator worked the rear ac worked whether I was plugged in or not. I guess what I should find out is once power leaves the generator how was that ac automatically powered? Is there a wiring schematic from the generator to the house?
Thanks
Ed

Maybe I don't understand your question.

Does your HR have an Automatic Transfer Switch?
Or do you unplug the power cable from the generator when you connect to shore power?

If you unplug from the generator to plug into shore power, that will connect all your 120 volt appliances.

Maybe a previous owner modified/altered the wiring?