If not properly installed inverters can be quite fickle. It doesn't take much to get them to misbehave. Incorrect grounds or voltages can cause a lot of headaches. Have you contacted the inverter dealer for any advice?
Here is a link to a site I found useful. It does say the document is in Beta test form, but everyone I have talked to seems to think this is good stuff. Has anyone else looked at this?http://www.equalccw.com/hardcore.html#INVERTERS
HARDCORE ELECTRICAL SYSTEMS:
Boondocker-Grade Energy Conversions For RVs
By Jim March © Sept. 2005.
As of 9/3/05 this document is in BETA TEST FORM
for review by qualified off-grid energy system engineers.
ALL INFORMATION SHOULD BE VIEWED AS