Looking/Hoping to find someone that might have had this issue that canhelp resolve this problem. The motorhome is a 2013 Thor Outlaw (Class A)The problem my buddy is having is that the moment he starts the engine on the motorhome he will lose all 110 electrical power to the coach.This will happen both when he is plugged into the shore power and/orrunning off the generator. He has been on the phone with Thor and they have sent him a new inverter last night and he installed and tested that a few hours ago and is having the same results. He has full powerwhen the motor is not running. The only time that he was able to correct the problem was when he disconnected all the batteries to the coach(House and Chassis) and when he tested it worked like it should until he shut the engine off and then restarted the power kicked off again. Thank you in advance for your time and effort in helping us get this problem resolved!!!ThanksSid Gage

My first reaction is to check the transfer switch but No 12V there on mine. So Back to the inverter but all of the AC power does not go through it on mine. Sorry but I do not come up with what is common to your problems if you are loosing all AC power. This could be "Very Interesting" when it's not my problem.

I would verify polarity of the coach battery system. It is possible when the charge relay energizes, it trips out the 12 volt DC coach system.

Ivylog - That was my first response to him also. That tested out okay. He can switch back and forth between shore power and generator. The system just fails when the coach motor is started.enblethen - All batteries have been disconnected/checked for damage/re-installedwith no issues to be found. I questioned him to see if he could test for back feeding from the engine alternator....Was just updated on the issue. He pulled the invertor out and hooked it up to another power source and failed to work. He was just informed by Thor that they may have a bad batch of invertors.... sending a different brand over night...

A bad inverter in a motorhome will generally NOT cause complete loss of 120 VAC. Said another way, the inverter should not be powering the roof A/C. Does the roof A/C work?

"he will lose all electrical power to the coach."All alternating current and all direct current?This is most interesting...

Losing Electrical Power when motorhomes engine is started.

wa8yxm
Explorer III
Jan 15, 2015
You said he is loosing 120 volt.. Let me ask,, Is it ALL 120 volt or just part of it.. The Front mounted Television for example.

If I guessed right.. There is a hint in what I posted (Working as designed).

If he's loosing power to air conditioners, Fridge, outlets all over the place, NOT working as designed.
BTPO1
Explorer
Jan 15, 2015
Chris Bryant wrote:
This really isn't a hard thing to diagnose- but it is near impossible long distance. Plug the coach in, start the engine, and see how far the power gets with a meter. When you find where power goes in, but doesn't come out, you have found the likely problem.

X2, totally agree with this method. Works every time. JMO
Chris_Bryant
Explorer II
Jan 15, 2015
This really isn't a hard thing to diagnose- but it is near impossible long distance. Plug the coach in, start the engine, and see how far the power gets with a meter. When you find where power goes in, but doesn't come out, you have found the likely problem.
Bobbo
Explorer II
Jan 15, 2015
Is he testing all of the outlets, or just the one powering the television in the cab?

The outlet powering the TV in my cab is wired to lose 110v power when the engine is running. It is a "safety feature" to keep the driver from being distracted by the TV while driving.
MrWizard
Moderator
Jan 15, 2015
does he have a "power management system"
if so it may have failed, or is sensing a voltage leak between the alternator chassis system and the power management system

try putting it in bypass mode
john_bet
Explorer II
Jan 14, 2015
If the control coils of the transfer switch are 12v dc they may be wired in such a way as they are switched off when the key is turned to start. This would open both sides of the transfer switch and dropping all power out. I would think it should not work this way---BUT????. Just food for thought as I have no experience with RV transfer switches, but lots with industrial type.
enblethen
Nomad
Jan 14, 2015
Can you locate the make and model of the inverter?
Does it have a remote control? It could be that the remote is wired incorrectly that when the rig is started it shuts the inverter off.
Dutch_12078
Explorer II
Jan 14, 2015
If the inverter uses an external transfer switch, that could be causing the issue. As said though, all AC would not likely be using the inverter. An answer to the roof A/C question might bring some light to the issue.
wolfe10
Explorer
Jan 14, 2015
Sorry, the roof A/C should NOT be run through an inverter. So, if the roof A/C is not working, look for another problem

IF HE IS SAFE WORKING AROUND 120 VAC, open the ATS and check the wiring. Same at breaker box. Since it affects both generator and shore power, it is between those two items IMO.
3GageBoys
Explorer
Jan 14, 2015
enblethen - I am told that the inverter is what Thor has diagnosed as being the problem.. I am having a hard time believing that all of a sudden a 9 month old inverter has gone bad and now Thor might have sent him another one that came from a bad batch. That is what it is if that is true... but i am still not sure how he can have power when the engine is off BUT when the engine is started he loses
110 power. To me something bigger is causing the power failure upon starting the coach.