Magnum inverter stuck on overtemp fault

Larry B · September 05, 2012, 08:11:03 PM

I have a Magnum ME2812 inverter in my bus that I cannot get to rest. It keeps getting a fault reading and coming back to overtemp. Tried holding on/off button for manual reset. Disconnected +12volt between battery and inverter- back to overtemp when 12 volt reconnected. Removed plug in cord to remote control box- same thing back to overtemp after self diagnosis. Plugged unit to 110 volt ac- same fault reading and overtemp. Will the inverter run without the temp sensing element that is installed under the neg 12 volt battery connection? Maybe my temp sensor has become defective. Are there any more tricks to get this unit to restart?? The inverted seems to think it is overheated. Every time the inverter is asked to restart the cooling fan in the inverter comes on. This fault light and overheat reading were on when I arrived home from a rodeo this weekend. (70 mile drive). I even removed the inverter cover looking for burnt pieces - none noticed. Any ideas on how to get this unit to fire up again would be appreciated or have I got serious problems? When it comes to electronics and electrical things I am most definitely NOT the sharpest tool in the shed. Thanks
Larry B

scanzel · September 06, 2012, 05:13:44 AM

Have you tried calling Magnum ? That would be my first palce to go.

Sean · September 06, 2012, 05:47:51 AM

Larry, the over-temp error has nothing whatsoever to do with the battery temperature sensor. Rather it has to do with the internal temperature of the inverter itself.

If you are getting this error even after a hard reset (described in section 4.5 of the manual on page 50), and there is no actual overheating caused by load or lack of cooling, then the inverter itself has a problem and needs to be repaired.

-Sean
http://OurOdyssey/BlogSpot.com

Oonrahnjay · September 06, 2012, 06:49:50 AM

Larry, on my inverter, let's say, if I disconnect everything on my bus, and let everything sit for a day, I consider that to be "cooled down" and "powered down". As soon as I either plug into shore power or connect the 12V feed to the house batteries, the cooling fan will instantly come on. My inverter is an Outback. I called Outback in Washington state and they told me that that's normal and the way that it should be designed. (I'm not convinced - why should the cooling fan run and draw power if the unit isn't warm?)
I know that Magnum and Outback will have differences in the way that software and controls are designed and also how the fault indications work, but how is your "overheat fault" shown? Is there a warning light? Do you have a remote read-out display for status and programming? I don't think that my unit has ever shown any faults -- it just runs the cooling fan any time that any power (120 or 12V) is connected to the inverter.
I don't mean to hi-jack your thread, but maybe our units are enough alike for us to both learn something.

Thanks, Bruce H NC USA

Larry B · September 06, 2012, 07:18:42 AM

I phoned the closest repair shop(200 miles away) that is listed on Magnum site for repair and they were closed yesterday due to family funeral. Will try again today. The fault is recorded on a remote control panel -red led light comes on and until fault is dealt with the unit will not start. The manual reset as described in the owners manual is the procedure I used. If the overheat is not battery sensor giving remote a signal then I do likely have a bigger problem. I will try the Magnum listed repair shop again today and see what he suggest.Thanks for input.
Larry B

Sean · September 06, 2012, 01:09:02 PM

Quote from: Larry B on September 06, 2012, 07:18:42 AM
.. If the overheat is not battery sensor giving remote a signal then I do likely have a bigger problem....

As I said, it's not the battery sensor. That's not what the over-temp error means. It's about the unit's internal temperature. There is a temperature sensor inside the unit itself which throttles back the charger as it heats up, and shuts down the inverter and/or charger if it exceeds certain limits. This same sensor controls the fans.

It's possible the internal sensor is bad, which would be an easy fix. It's also possible there is some other problem with the unit which is causing it to actually overheat, such as a short in the battery charger, output transformer, etc..

If you didn't care about the warranty, you could open it up and look. A short or other major problem should be pretty obvious. Changing out the temperature sensor should be straightforward, too, if you can read the part number off it.

-Sean
http://OurOdyssey.BlogSpot.com

Larry B · September 07, 2012, 08:04:13 PM

I got to talk to the Magnum repair shop late yesterday. He had me push "tech" button on remote and rotate scroll . This showed different internal temps before fault happened, as you stated Sean. BTS(battery temp sensor)-22C, Tfer(transformer)-19C, FETs-192C I can"t remember what last stood for. From this he said the main circuit board was likely the problem. Sean, I have no warranty left so I opened it, visually I saw nothing wrong. Anything more than visual is beyond my capability. He would send a new board if I wanted to try changing myself, but if it didn't correct error I would still have to pay for board. Board needed to be torqued down, and person and unit should be grounded when working on. Sounds as if I could easy mess up. Will ship to him tomorrow (on the other bus). Told him not to ship back, I would bring my unit to him (200 miles away) after he had it repaired. I would do grunt work and bolt back in, and he could connect wires and make it work again. He aggreeded to also check the rest of my wiring in case I have done something to cause this issue. I know I will not like the bill but it needs to be fixed . I have taken a few pictures to show what the inside of inverter looks like with cover off. Going to go for a little drive to Ontario to visit friends for two or three weeks. so repair should be done when I get back. If you look in the background of a couple of pictures some of the steel support for my slide is shown with guide rollers.
Larry B

Larry B · September 07, 2012, 08:06:38 PM

More pictures

Jeremy · September 08, 2012, 02:39:05 AM

Quote from: Larry B on September 07, 2012, 08:04:13 PM
...FETs-192C I can"t remember what last stood for
Larry B

FETs are Field Effect Transistors, and it looks like yours are fried (registering 192'c). Years ago when I was heavily into racing RC cars the FETs would blow in the speed controllers, and we would solder in replacements. If you think about it, a speed control is doing a similar voltage-changing job to an inverter, so it's reasonable to think that a similar failure scenario would occur.

Jeremy

Sean · September 08, 2012, 07:00:21 AM

Sounds like blown MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), as Jeremy says. Those can probably be replaced by any qualified electronics repair, as they are off-the-shelf items, but testing the board afterwards without the right bench setup would be impossible. The good news is that it should be a simple repair, so the bill should be a good deal less than a new inverter. FWIW.

I did not know about that tech menu (not in the user docs), so that's good to know.

-Sean
http://OurOdyssey.BlogSpot.com