I would expect that this is most likely a isolator problem. You should be able to check and see if your getting power to your house battery now that the disconnected the "cap". If they had not bypassed the unit it would have continued to do damage to your new alternator. It would have been nice that they could have helped resolve the issue, but at least they didn't just throw in the new stuff and send you are your way. The isolator will look like this:
If they bypassed your isolator you will no longer be getting power to the house battery, running starcool even while driving would reduce house battery very quickly.
I have also included instructions on how to test a isolator;
Instructions for testing a isolator,
INSTRUCTIONS FOR TESTING A SURE POWER ISOLATOR WITH OHMMETER*:
1. Remove all wires from the isolator.
2. Using a needle movement ohmmeter RX-1 scale or a digital ohmmeter diode scale, hold the Red* probe on the terminal "A" and with
the Black* probe touch terminal #1 and #2, and the "E" terminal for 3A isolators (group 2), and the "R" terminal for (group 3) isolators.
A good isolator will show a current flow from "A" to #1, #2 and "R", and no current flow to "E".
3. Next, hold the Black* probe on the "A" and with the Red* probe touch terminal #1 and #2 (terminal "E" and "R", if used). A good
isolator will allow no current flow from "A" to #1, #2 or "R" and will show current flow from "E" to "A".
4. Hold one probe on the aluminum heat sink, being sure there is contact by scratching through the protective coating. Then touch
with the other probe, terminals "A", #1, #2 (the "E" terminal for 3A isolators [group 2] , the "R" terminal for group 3 isolators). A
good isolator will show no current flow.
5. Colored terminal indicates "E" post on group 2 isolators and "R" terminal on most group 3 isolators.
*On some import ohmmeters, the red and black probes are reversed for these tests.
**If using a digital ohmmeter, a diode scale MUST be used.
You also may have a circuit breaker between #2 and house battery that has gone south. If you are using the E terminal it is also probably fused.
A trip to sportsmobile may be your best option they could take care of that and look at starcool.