View Full Version : Why is my fridge blowing fuses?

03-26-2012, 11:37 AM
I have a Norcold MRFT-60. It is the same thing as an Engel MT60. I have popped three 10 amp fuses in the past 6 months, under constant use. Per their technical specs, the most it should draw is 3.6 amps http://www.engel-usa.com/index.php?page=shop.product_details&flypage=vmj_genx.tpl&product_id=25&category_id=1&option=com_virtuemart&Itemid=59

Yesterday 60wag came over with an Ammeter and we measured at most 5 amps during its cycle. We didn't see any spike at start-up either, just 0 to about 4.5... it was camped out at 4.5 pretty much the whole time while running.

I am running this in the truck direct off a 2nd battery, which is isolated from the starting (so no voltage spike). That battery has been a Super Start AGM (Deka) and most recently a Die Hard Platinum marine- they both can blow this fuse equally. The fuses that have been blowing are in the cable of the posi-fit harness http://www.sierraexpeditions.com/index.php?l=product_detail&p=1001

After the + side blew, I put a 20 in there (didn't have a 10). Now that the - side has blown, it's also got a 20. Now don't panic kids... 4' upstream I've got a fuse block where I have 15 amp blade fuses-. And yes about 6' upstream from that one I've got a 100 amp fuse, right off the battery. My grounds are rock solid, a 4ga wire runs off the fuse panel to the frame below.

I have yet to install the fridge again after this most recent experiment, and swap to the 20's on both sides of the harness- I need to unload a crib first to create space. Customer service guy at Engel said that I need to run their thermal fuses... they allow for a wider operating temperature than a standard automotive fuse, he's sending me a couple to put in place of those 20's. He also confirmed about 5amps sounds normal (no, I didn't mention the web site says 3.6). Any other thoughts from the masses here?

03-26-2012, 11:41 AM
Assuming there isn't a short in the path or too much resistance in you wiring (too many fuse junctions, crappy wire, etc.) Go to the store and buy a U.S. made 10amp 3M fuse. Resistance = heat so feel and inspect everything for signs of heat. Melted fuses or fuse holders is what I have found most often. Corroded wire can do it as well so you may want to look into tinned wiring for boats. The stuff they sell at Home Depot or the auto stores is junk.

On a possibly related topic, Snowruns blew all sorts of things when his positive terminal worked loose. Every time it reconnected, the voltage spike was too much all at once and things melted. This is an unfortunate side effect of buying these huge batteries with massive capacities. One little short and it welds just as well as it keeps beer cold for extended periods of time.

03-26-2012, 12:02 PM
Mike, you talking about the positive terminal on the cigarette lighter plug? I tossed that when I upgraded to the posi thing, after I melted the one on my Edgestar I'm not loving those connections as much. Though the Engel cord is of considerably higher quality, and to its credit the one I put in the 80 is probably keeping beers cold in Las Vegas right now, so 6-7 years and still going strong. And to continue that comparison, the wiring quality in my 100 is at least twice as good as the 80- lots more crimp connectors & shrink wrap, much less electrical tape.. :hill: I feel pretty good about the wiring quality here.

I have felt around for excessive heat, but tough to do when some of it is buried behind plastic panels, plus when I discover I've blown a fuse it's usually hours after it happened... hop back in the truck and it's ominously quiet then I realize the light isn't on anymore.

03-26-2012, 12:58 PM
You need fuses that can take the startup load. Normal fused will blow. Get the real engel fuses or a slow burn fuse.

Also I can't figure out if you have it hardwires or on a plug. If it is on a cigaratte lighter change it to hardwire.

03-26-2012, 01:44 PM
Posi-fit is essentially hard wire. and Engel fuses should be here Wednesday. for free, I should add.. nice folks over there.