Originally Posted by Dutch1999
Looking for help with my Marquis 7000 generator. It runs but doesn't power my air conditioning in my 1999 Newmar dutch star 3884. The air conditioning runs on shore power. I have replaced both breakers to no avail. Not sure how to test the Automatic Transfer switch and would be willing to convert to a manual plug in if necessary to avoid replacing the switch for big dollars. Reading many posts and watching YouTube videos but not alot for my problem or unit
What transfer switch do you have?
If it's like mine, replacing a faulty contactor or a circuit board is a cheap alternative. Those are about $80.00 each.
On my Esco ES50M-65N it's easy to diagnose (once I get there as it its mounted to a difficult to reach location).
On the pic below shore line input is on top top right and generator input is bottom right (ALTERNATE).
The output side (LOAD) is tied together on the left side from shore contactor to the same posts on the generator contactor where it says "Do Not Use".
When the shore power is used (generator off), you should see 120V between Hot one and neutral. Same between Hot two and neutral. And nothing on the generator input side.
Then on the output (Load) side, you should have the same 120V between Hot one and neutral. Same between Hot two and neutral. And obviously the same on the generator contactor output side since they are tied together.
When shore power is off and generator is on, you should see the same input and output 120V readings on the bottom contactor: 120V between Hot one and neutral, 120V between Hot two and neutral.
If the generator input terminals have no power, you probably have a tripped circuit breaker in the generator or bad contact (maybe corrosion) on the generator cables.
If the generator input has power but not the output, then the contactor is bad. Or maybe the circuit board not making the switch. You can get both from Esco USA.
You can see a circuit board on the right side tied to both contactors. That controls the switching.
If both on shore power and generator are running, only one of them should pass current thru to load side. Typically it's the generator but could be either one.