Community Forums

**CountryFit** · 01-22-2022, 10:27 AM

My inverter is a Magnum MS2812. Woke up in the morning last week, fridge and wall outlets were out of power. Looked at the remote, a red LED with message "Internal Power". Did a hard reset, a new message showed up "Internal Bridge". Looked up the Magnum manual and realized it could be a real failure on one of the boards. Though I was on shore power, the inverter simply won"t pass through the power.

Tried to contact Magnum, the phone number led to their subdivision in Minnesota. Left a message but they have never bothered to call me back even to today.

Called a factory authorized dealer in the area, the technician thought the FET board might be bad, need a further inspection. A new board was quoted $700 plus tax and would take 2-3 weeks to arrive if the factory stocked it. With parts and install the total cost could be just about a new inverter.

I decided to take it out and bypass it so I could have the power in the coach. The pulling was just a reverse process of my install in 2016, no drama there.

Once I opened up the case, I was rather lightened up - the wire was visibly burned out, that'd certainly be an easy job!

Close up the burned wire:

Further inspection revealed that other ends of wires were burned too:

Replaced the wires, and tested it, all was good:

But, I thought it over why it had been overheated so badly at that corner. At the end, I believed it was the bad design. The area has the AC board, and the filter board on the top, the heat from the AC board and the adjacent transformer was trapped at the corner. Why didn't they make the case corner on the side and the front like other areas with grilles? Please share if you know the answer.

I made the mods. Now the front and the side have the grilles.

Considering this inverter had been about 10 years old, I replaced the original two cooling fans. Put everything back in place, now it does its job as expected.

The moral of the story is - if you run into an overheat issue, you might check the corner out.

Happy travels!

dons2346 · 01-22-2022, 09:10 PM

Interesting mod Steve, thanks for posting.
My former live, I was involved in failure analysis and I'm always interested in the reasons a piece of hardware lets the smoke out

**CountryFit** · 01-23-2022, 06:54 AM

Yep, we got to get to the bottom of the failures, the root causes; or they would come back to get us

.

YC1 · 01-23-2022, 09:17 AM

Great report. Had the same issue on a later model one. It had just one bad connection and was an easy fix.

Is the area where the inverter lives well ventilated? Mine has a fan at the end of the compartment that is controlled by a snap disc. Keeps the compartment at least at ambient temps versus hot enough to bake muffins.

**CountryFit** · 01-23-2022, 10:15 AM

Quote:

Originally Posted by YC1

Is the area where the inverter lives well ventilated? Mine has a fan at the end of the compartment that is controlled by a snap disc. Keeps the compartment at least at ambient temps versus hot enough to bake muffins.

I installed a blowing fan for the entire inverter compartment controlled by a thermo switch, a few years ago. It turns on at above 104f and moves the hot air out of the battery bay. The inverter compartment is virtually always at ambient temp.

BonS · 01-23-2022, 05:07 PM

I would presume that it's a NEC/UL thing for the lack of louvers in that area. There are standardized probes that we'd call UL fingers that are used to address openings in enclosures. There's 120 VAC very close to that area and it likely had to be protected from the finger.

I see that both ends of the overheated wires are blackened. It's hard to tell but perhaps both wires were attached with Faston style connectors? If so then the crimped connection was the weak point which led to overheating, corrosion, and over temperature failure.

If one end was soldered then it was likely a cold solder joint that eventually failed with thermal cycling. Resistance went up and that means heat was produced.

I doubt that properly assembly, using soldered connections, would have overheated like that. The heat was produced from resistance and current. The engineering term is I-squared-R losses. Wattage = heat = current * current * resistance of the connection. If the connection resistance is zero then no wattage (heat) is produced.

It's not like I need another project, but you're motivating me to tear into my Magnum and check the interconnect wires before the magic smoke gets out.

**CountryFit** · 01-23-2022, 09:08 PM

Quote:

Originally Posted by BonS

I would presume that it's a NEC/UL thing for the lack of louvers in that area. There are standardized probes that we'd call UL fingers that are used to address openings in enclosures. There's 120 VAC very close to that area and it likely had to be protected from the finger.

I see that both ends of the overheated wires are blackened. It's hard to tell but perhaps both wires were attached with Faston style connectors? If so then the crimped connection was the weak point which led to overheating, corrosion, and over temperature failure.

If one end was soldered then it was likely a cold solder joint that eventually failed with thermal cycling. Resistance went up and that means heat was produced.

I doubt that properly assembly, using soldered connections, would have overheated like that. The heat was produced from resistance and current. The engineering term is I-squared-R losses. Wattage = heat = current * current * resistance of the connection. If the connection resistance is zero then no wattage (heat) is produced.

It's not like I need another project, but you're motivating me to tear into my Magnum and check the interconnect wires before the magic smoke gets out.

Ha, the NEC/UL thing, the finger probe makes a perfect sense. Interesting to learn the nitty gritty stuff

Yes, both ends of the terminals were/are flat-blade type (Faston type). Granted the crimping contact wouldn't be as good as soldered. I'll keep that in mind if I need to do it again down the road, hopefully don't have to

.

A side note. Per my inspection, the FET board and control board are built very solid, unlikely these would go out soon. Keep an eye on AC board. There are two cooling fans (92mm x 92mm x 25mm at 65 cfm), the lifespan of the sleeve-bearing fans is typically about 30,000 hours, approximately 5-6 years. If you get an over-temp incidence on the remote, you might check the wires in the corner, and replace the fans while you are at it.

Happy trails!

birdhunter · 01-23-2022, 11:42 PM

Very impressive CountryFit!

**CountryFit** · 01-24-2022, 09:54 AM

Quote:

Originally Posted by birdhunter

Very impressive CountryFit!

Thanks. Just wanted to make it right

.

Smitty77 · 01-31-2022, 02:52 PM

Super informative INFO sharing.... Salute to the Can Do fix and improvements.

Best,
Smitty

**CountryFit** · 01-31-2022, 05:30 PM

Quote:

Originally Posted by Smitty77

Super informative INFO sharing.... Salute to the Can Do fix and improvements.

Best,
Smitty

Have been receiving much help from you all over the years, this is just a small piece carrying my undying gratitude!

Vizjedi · 02-04-2022, 03:32 PM

Nice find and fix. I also have a dead MS2000. I was hoping to find something obvious when I pulled the cover, but nothing apparent. Did the same as yours. Stopped inverting, charging and won't pass AC shore power through. I'm leaning towards the TACB AC control board, partly because it is only $275, but others have said it could be the FET. That one is $700 if you can find one.

I bought a Progressive Dynamics inverter and have it in now. It was about $550. I have a 2nd inverter/charger for the residential fridge, so don't need the charging function on the replacement, but it would be nice to have the old Magnum fixed.

j

lwikle · 02-23-2022, 04:37 PM

Magnum SUCKS

been waining on a replacement under warranty ms2812 since JULY!!!!
Just got an email saying it will be another 3 months......supply chain blah blah blah..........wont answer phones. I could go on and on....NEVER AGAIN

Luther Wikle affinity 6600

**CountryFit** · 02-24-2022, 09:59 AM

Quote:

Originally Posted by Vizjedi

Nice find and fix. I also have a dead MS2000. I was hoping to find something obvious when I pulled the cover, but nothing apparent. Did the same as yours. Stopped inverting, charging and won't pass AC shore power through. I'm leaning towards the TACB AC control board, partly because it is only $275, but others have said it could be the FET. That one is $700 if you can find one.

I bought a Progressive Dynamics inverter and have it in now. It was about $550. I have a 2nd inverter/charger for the residential fridge, so don't need the charging function on the replacement, but it would be nice to have the old Magnum fixed.

j

Did you take it apart and see any signs of failed components? Bulging capacitors or burned resistors could be easily identified if those were the causes. Keep it and someday you will get it fixed

.