manholt Report post Posted January 14, 2016 Does it also happen on generator with invertor and charger on? Other thought is dead cell. Share this post Link to post Share on other sites
huffypuff Report post Posted January 14, 2016 Is that the relay solenoid on the back wall above the batteries? Share this post Link to post Share on other sites
rdjl972 Report post Posted February 9, 2016 OK. I promised an update when - and IF - I was able to figure out what happened. It turns out that the Big Boy relay will make the "thumping" sound whenever it's trying to charge a battery that's low on charge. In our case, that was the engine start batteries - two group 32 maintenance free batteries in parallel. These are our older batteries - 7 years plus - so all I had to do was replace the two start batteries and the problem went away. BUT ... I'd like to give credit, where credit is due. In this case Mark and Chris at M & M Audio mnmaudio@roadrunner.com were an excellent source of information about the Big Boy relay. They explained everything I needed to know and more. They even mentioned stuff I hadn't even thought of. What a great help they were and I wholeheartedly recommend them to anyone having battery and/or charge problems. Send them an email and see what you get. Thanks again to everyone that helped me. Rick Share this post Link to post Share on other sites
rwilli Report post Posted February 9, 2016 Rick, Please post your findings as inquiring minds want to know. I have a 2008 Dynasty and we also go through that annoying thumping coming from the rear electrical box relay. This happens ocassionally and I am assuming your assessment is correct--the thumping appears to be connected to low chassis/house battery banks. We even added a trickle charger on the chassis battery to aide in the charging process--but this actually seemed to exaerbate the thumping. However, once the coach has been connected to shore power for a few days all becomes quiet and stays quiet. Share this post Link to post Share on other sites
