Well.... I have a 2005 Damon Intruder 377w
The house batteries
NOTE: if you operate what we here call the Salesman Switch, which on my righ is marked USE/STORE (it is a 3 position rocker) and is in the stair well, And put it in the STORE position (Disconnected) Generator will not start.
Suggestion #1: Check that switch, then check for battery charge (As someone else said do the interior lights work?
IF you can not get lights workign you may have to replace battery (Batteries) See below for suggestions
Start Main Engine, wait one mintue and then try to start the generator (Off the chassis battery this time)
Keep main engine running for at least one minute after generator starts.
Battery suggestion.
Assuming you have two Six Volt batteries in series... KNow that these two make up a single 12 volt battery (Roughly a 4D) when installed. Treat them as such.
On mine the POSITIVE side is to the rear (no reason yours should be the same) but Identify the POSITIVE side and using some RED nail polish or tape clearly mark or tape all wires connected to this terminal.
OPtional use BLACK on the most negative terminal (Do not worry about the jumper wire, it can safely be reversed)
Then DISCONNECT the wire(s) connected to the NEGATIVE end, if there is more than one tie them together with string or a bolt or a zip tie through the lugh eyes
Then do the same on the POSITIVE end, insulate these wires by sticking the ends in some thing that insulates.
Then the jumper
Then have fun getting those things out of there
Test them before buying new ones.
REplacment is the reverse procedure
What to buy: On my coach the original batteries were INterstate U-2200s Very good, lasted 9 years with abuse
I replaced 'em earlier this year with DEKA G20 (230 amp hours, same footprint)
Sams Club and Costco have GC-2 at a very attractive price if you are a member
Trojan is considered by many to be the best but I do not think they are that much better than the above.
Finally.. IT may be all you need do is a clean and polish on the terminals.. That has fixed me up a few times.
Oh and once, the salesman switch failed.. It would disconnect nicely but refused to re-connect,, I fixed it too.