Aux Start to Boost Cranking Amps

Yes it will kind of work. But you might want to load test that battery (S).

Just an update.
After I returned home I found that the plug from the front left jack was not completely plugged in at the controller. Since I have repeated the plug I haven't experienced any more problems.

I just leave mine running while jacks go down and slides go out. But should not hurt to use start button.

Update
Drove 4 hours Monday, parked RV, kept engine running, battery showing 13.5v, went to lower jacks, jacks down led came on and jacks went into error mode. Going home tomorrow and will do more troubleshooting this weekend.

Yes .... Arrive at destination, batteries should be charged from driving, leave engine running, use the jacks to level the RV
If you need to use the aux start switch to boost the engine battery, you have 2 problems, a weak chassis battery that should be replaced and a charging system that is not working correctly, because the house and chassis batteries should already be combined when the engine is running,
There is an exception to this
If your MH has a diode based battery isolator instead of the battery control center box, that is common on many MHs

A diode style isolator let's both batteries charge while keeping them separate, if you have this then yes you must press the aux start switch to combine them to provide extra power to the chassis system for the jacks(if chassis battery is weak)
The BBC cost more $$ takes more time to install than a diode isolator, so some RVs do not have the BBC, but instead have the less costly diode isolator and a less costly momentary duty relay for the aux start function
Instead of the heavier more reliable continuous duty relays used in the BCC

DrewE wrote:
I agree with everyone--yes, it is okay to do that.

However, there's a pretty good chance that pressing the button isn't actually doing anything with the engine running, since a very common setup is to use the aux start solenoid as the battery combiner/isolator relay and have it engaged whenever the engine is running.

Yes. I agree with Drew, AND with Doug. AND, . . . . the chassis battery, AND coach batteries are, most likely, ALREADY CONNECTED (without pressing the AUX switch) since the (chassis) engine is running. HOWEVER, the OP doesn't state the RPM that the engine is running which WILL have a significant effect on the available amps from the chassis alternator. At idle, with low batteries, IMO, the alternator is only generating enough amps for basic electrical functions. (running the Power Gear electric leveling system ISN'T one of them) Revving the engine for a few minutes could/may help. Recharging the coach/chassis batteries will.

Chum lee

I recommend a Trik-L-Start combiner or similar so the chassis battery will be kept charged.
You will get more years and miles out of the battery too.

chuckftboy wrote:
That's confusing. You said if the engine is running and if it is, the alternator should be suppling the power for the levelers. The alternator should be able to supply all the power needed.
To answer your question...yes you can use the boost switch with the engine running.

Absolutely wrong. Alternators cannot give the AMPERAGE needed to run heavy duty appliances like a 12 volt Jack system or a hydraulic jack system pump. That is why the jack system makers will state to have a GOOD fully charged 12 volt battery in the system.
YES, on the Aux Start. BUT when the engine is running, the AUX start solenoid is already engaged, so you do not have to hold the Aux button. Be advised that some AUX start systems require up to 5 minutes after the Engine is running to engage automatically. If so, you can then push the AUX start button to get immediate coach power to the Chassis system instead of waiting that 5 minutes. Doug

On my rig the Power gear system wanted ENGINE RUNNING. And this not only meant the alternator was pushing more amps but the two banks were joined by the Isolator. Sadly it still failed.. Happily it's not may problem any more.

chuckftboy wrote:
That's confusing. You said if the engine is running and if it is, the alternator should be suppling the power for the levelers. The alternator should be able to supply all the power needed.

Concur ! At worst, hold the engine at high idle.