[tobflyin]

Hi Folks,

I've searched the forums a bit but I know everyone has different air setups. I also watched the youtube videos which were quite helpful in understanding the basics but I'm trying to understand how my coach works as it has a different setup than the ones mentioned on the video.

From my understanding, I have dual 120v Thomas compressors up front, and then the engine driven air pump (no 12 volt compressor). When letting the coach sit for a day, the front compressor pressure drops to zero, but when I turn key on to check primary and secondary pressure it still reads anywhere between 95-110. I also noticed when we purchased the coach that when the engine was running, we would occasionally hear the front compressor come on. I inquired on this and the seller thought this was normal. 

So, my question is:

1. Should the front compressor run at all when the engine is running (assuming it has built up engine pressure).
2. I would assume there's a shutoff to keep air for the chassis when it falls below a certain point, is that the case? And at what pressure should it isolate?
3. If there isn't a shutoff, how could my front compressor gauge read Zero but my primary tanks read 100?

I am planning on fixing all the leaks and hooking it to shop air, but it would help to understand the systems a bit and fix other issues while I'm there. From what I have read, the older design with 12 volt compressor had different pressure settings for the 120v and 12 volt compressors (far less then engine pump), so they wouldn't kick on until it dropped to different given points. But, I think the 120v dual compressor setup is set to kick on around the same pressure as the engine compressor. This may explain the front compressor running with engine running, but wouldn't explain the front dropping to zero when the coach sits without losing a lot of air from the primary. Anyone with my vintage or perhaps newer coach have my type of setup?  I welcome any/all suggestions!

Thanks all,