Understanding AUX-START with generator

beaubeau wrote:
Super!
This makes sense, thank you. All except that the generator doesn’t run even if the chassis engine is running, unless AUX-START is held down.

dougrainer wrote:
2008 Tiffin. The chassis starts the Genset. It takes 12 volts continous for the Genset to run. Gensets do not supply 12 volt power once they are running. So, you got the Genset started with the Battery boost button. It takes the COACH batteries to engage the battery boost. So with the battery boost button pushed ON, your Genset started from the coach batteries and the coach batteries supplied the 12 volt power to keep the Genset running. Once you released the Battery boost, the Genset and Chassis side LOST the 12 volt signal. Hence the Genset died. Have you tried the same operation but start the Engine first and leave ON? Then boost to start the genset. The Engine alternator will supply the 12 volts required to keep the Genset running. Doug

This means your alternator charging system is NOT getting voltage to the chassis battery. ALL your boost switch does, is, combine BOTH the chassis and coach battery banks together while the switch is held. On Tiffins your year, there is a addon solenoid Tiffin installs that routes alternator current to the chassis battery. Also, in extreme cases, the RV owner has MISSED installing the extra Positive cable on the chassis battery for the Genset and charge. They have done this when replacing the battery or disconnecting the chassis battery cables. I have seen this more than a dozen times on Tiffin's where the owner will swear he has all cables connected and he comes in and I walk out and show him the pos cable NOT connected. 1. It is usually BLACK/ 2. Since it is black he connected to the negative. Doug