I have the Itasca detailed below, and lately has developed an issue where the dash fan will only work on the high (noisy!) switch setting. After starting the engine (Chevy workhorse 8.1 engine chassis...
Don't replace anything until you prove what is wrong. This may help to further troubleshoot. Notice in this video that there are 2 relays. Not that it's exactly your system. just one example.
