Replace FET Board on Magnum 2012 Inverter

[alaskawalker]

Can anyone tell me how I can replace a bad FET board in my Magnum 2012 inverter? On a Holiday Rambler Neptune.

I have the neq FET board, but no clue how to replace it. unfortunately there are no mechanics available. I am without any power.

[Martinvz]

On Youtube are some videos of the inverter repairs. Search for “Rvdiagnostics inverter rv” that explains some of this. You will also find some other related videos and may provide the details you need.

[Mike Wardell]

It's really not that hard, just take your time. I unbolted my inverter to gain easier access. Remove the top cover and you will see the FET board. Take pictures or mark the wires you remove. 

[Tom Cherry]

Based on the age of your inverter, when you tear it down, you need to look around.  Since you are doing the work yourself, then there are temperature sensors.....and fans.  These are the LIFE of your inverter.  If the fans do not work, it will cook the new board.  

Don't know if you called Magnum or have talked to them.  In helping members here, I talk to them at least once every few months. Generally, the techs recommend a complete replacement of the Inverter if you need a new  Control Board.  Now....I THINK I am on the same page with you.  The main control board or the PCB has all the electronics as well as the "Switching" relay.  That is like an ATS within the Inverter....it either lets power through (if incoming AC) or switches to Inverter and it gives you power.  The cost of an authorized dealer making the swap varies all over the map.  What they say is that the board plus the labor is typically more than 50% of the cost of a new inverter....assuming you can do the changeout....which will, for you, be childsplay.  That is what we post here.

I would call Magnum and ask them WHAT to look for.  I am a little flaky on the sensor....it MAY (probably is) part of the PCB you are putting on.  But, there is at least one or maybe 2 fans in there.  You REALLY NEED for them to work otherwise, the inverter will overheat....GOOD BYE FET.  I personally would never run the inverter at more than 80% Charge rate.  I KNOW that you live in a COLD area.  Magnum sets the charge rate, I think, for 100%, but some of the techs have told me to cut it back to 90%....and then others, based on the fact that mine is 13 years old....to set it at 80%.  

Magnum tech will tell you what parts you might want to look at or change out as a precaution.  I would have compressed air (can or compressor) and some ELECTRONCIS....NOT ELECTRICAL cleaner and if you need to get the crud off the fans....assuming they are OK, then do that.  

Good Luck....let us know how it goes.  You will be one of the first, I recall, to do this.  But, the Magnum techs told me that it was not a bad job....but that most of the folks that called in were not "experienced"....BUT, they will also tell you any issues to be aware of.  Great folks.

FINAL issue.  Please update your profile and list the Year and Model number.  That helps folks with giving you assistance.

 

[CAT Stephen]

5 hours ago, alaskawalker said:

Can anyone tell me how I can replace a bad FET board in my Magnum 2012 inverter? On a Holiday Rambler Neptune.

I have the neq FET board, but no clue how to replace it. unfortunately there are no mechanics available. I am without any power.

I have a Magnum 458 Freedom inverter with two (2) 20A 120VAC circuits in excellent condition that I had to pull last week due to my changeover to Lithium batteries.  If you elect to replace your inverter, I can sell my inverter to you for a reasonable price and at a fraction of the new price.

[MyronTruex]

https://www.youtube.com/watch?v=1UusJigPuG8

This video may help.

[JohnC3]

I may be mistaken as I don't know your rigs electrical setup, but my old Magnum 2012 ran off a breaker in the circuit box. If you have NO power, the Magnum should only impact a few receptacles and the microwave. 

Even if the Magnum was somehow impacting the system, I would THINK you could isolate it by turning the inverter breaker off and that should allow you to have shore or generator power to everything except the microwave and a few outlets.

[Tom Cherry]

8 minutes ago, JohnC3 said:

I may be mistaken as I don't know your rigs electrical setup, but my old Magnum 2012 ran off a breaker in the circuit box. If you have NO power, the Magnum should only impact a few receptacles and the microwave. 

Even if the Magnum was somehow impacting the system, I would THINK you could isolate it by turning the inverter breaker off and that should allow you to have shore or generator power to everything except the microwave and a few outlets.

The Magnum has to be on and “seeing” or getting 12 VDC from something resembling a battery…presumably then trying to charge the less than robust battery.  If not the ATS on the control board or the FET aboard of the Magnum will not pass power through.  Yes, you will not have power on the Microwave or any (all or most) of the convenience outlets that are on the other circuit…typically GFCI controlled.  Therefore you would have power to the AC and such, but if the house batteries are dead or inoperative, then the Magnum would not work nor would not provide 12 VDC power to provide lights for the motor home…nor the thermostat.  NO AC.

The only workaround would be to put a jumper cable on the House and Chassis positives.  The Magnum, if it is OK, would be getting voltage from the Chassis and start charging the Chassis and then there would be enough voltage for the inverter, assuming the relay or ATS on the control board would allow pass through. Then the House fuse panel would be energized and all would be well.  Sort of like locking in the Boost switch.

Lots of IF’s and such, but that is the way it works.  

[JohnC3]

Thanks Tom, 

So with depleted 12V House Batteries (or a broken inverter control board) You would be unable to charge 12V Batteries, So with a bad inverter, No power to the 2 circuits on the inverter and in time no power to the 12V house power system. But if you were on Shore power, would this lack of 12V House power prevent the EMS from functioning? (My instincts think it could, as the EMS relay control board has 12V input to it.)

Useful info, I should have thought of the 12 and 120 volt system control being intermingled in the EMD control board. 

Thanks, Its always useful to learn a little more about our snowflakes!

[MyronTruex]

10 hours ago, JohnC3 said:

Thanks Tom, 

So with depleted 12V House Batteries (or a broken inverter control board) You would be unable to charge 12V Batteries, So with a bad inverter, No power to the 2 circuits on the inverter and in time no power to the 12V house power system. But if you were on Shore power, would this lack of 12V House power prevent the EMS from functioning? (My instincts think it could, as the EMS relay control board has 12V input to it.)

Useful info, I should have thought of the 12 and 120 volt system control being intermingled in the EMD control board. 

Thanks, Its always useful to learn a little more about our snowflakes!

You could test the theory by turning off both banks of batteries and the charger portion of the inverter/converter as well as any solar.

The EMS installation manual calls for 12 volts input so I think your instincts are correct.