Fridge fuse overheating with fridge running on 12V.

[runnach]

As per title, I actually found a blog from a motorhome couple ( Bloggers ) who have experienced exactly the same within their fuse box area, and their blog give great detail. What I will add is, the heat generated due to resistance, was hot, so hot, the fridge fuse holder tabs have lost their temper and fuse spades (spring steel) have very little grip. Attached images are from our MH.

I have also been liaising and have received very good advice Wildebus ( David ) and our conclusions are to keep the current fuse box, as it is fine, now I need to trace fridge cable from fridge to fusebox, then create and install a separate fuse for fridge which will bypass fuse box completely.

Reason for post, what the bloggers and I have experienced is a fire hazard, this post is to make you aware of this potential risk within your motors, and to periodically inspect fridge fuse holder.

RV Motorhome fires- causes & essential prevention tips

Concerned about motorhome fire? Honestly, we weren't... until it happened to us. Here's the story and how to prevent RV fire in the future!

www.wandering-bird.com

 

[Exwindsurfer]

As per title, I actually found a blog from a motorhome couple ( Bloggers ) who have experienced exactly the same within their fuse box area, and their blog give great detail. What I will add is, the heat generated due to resistance, was hot, so hot, the fridge fuse holder tabs have lost their temper and fuse spades (spring steel) have very little grip. Attached images are from our MH.

I have also been liaising and have received very good advice Wildebus ( David ) and our conclusions are to keep the current fuse box, as it is fine, now I need to trace fridge cable from fridge to fusebox, then create and install a separate fuse for fridge which will bypass fuse box completely.

Reason for post, what the bloggers and I have experienced is a fire hazard, this post is to make you aware of this potential risk within your motors, and to periodically inspect fridge fuse holder.

RV Motorhome fires- causes & essential prevention tips

Concerned about motorhome fire? Honestly, we weren't... until it happened to us. Here's the story and how to prevent RV fire in the future!

www.wandering-bird.com

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That doesn't look good at all Terry

 

[runnach]

That doesn't look good at all Terry

Pic two Jeff, fuse holder immediate right of yellow fuse within its holder. Red neon light fried. Spring steel discoloured due to heat generated, also note the gap within same holder, this is what I meant with that holder loosing its temper, using thin long nose pliers, I could close the gap, then when fuse was re-inserted, holder opened up with poor grip to fuse spades and adding to resistance = heat.

 

[Exwindsurfer]

Well at least you are getting it sorted with out a fire

 

[merl]

Yep, the fact that the 12V side only gets used whilst the engine is running means that the voltage is considerably higher, probably over 14V, this leads to more current than the manufacturers state (because they rate them at 12V) and often close to an actual fuse rating of 15A, this in itself will cause a lot of heat from the fuse, add this to the heat from old tarnished fuse connections and you've got a concentration of heat in a very small space, the hot metal loses it's bite on the blade and things get worse.
Had a similar experience with the blade fuse on a charger, got hot and melted everything near it into a ugly glob.
I reckon 10A is absolute max for a blade fuse, anything more should use a better type suitable for high currents.

 

[Sonar]

When you say a blogger had the same problem. Were they both the same fridge.
Or both the same motorhomes or vans .

Or just by chance both had the same problem..

 

[merl]

When you say a blogger had the same problem. Were they both the same fridge.
Or both the same motorhomes or vans .

Or just by chance both had the same problem..

It's not a van/MH specific problem.
It could happen to the blade fuse/holder in any van with a 3 way fridge that's used on 12V.

 

[runnach]

When you say a blogger had the same problem. Were they both the same fridge.
Or both the same motorhomes or vans .

Or just by chance both had the same problem..

Common denominator is, we both had the same fuse issue, regardless of vehicle type, with 12v setting utilised with engine running.

 

[wildebus]

It's not a van/MH specific problem.
It could happen to the blade fuse/holder in any van with a 3 way fridge that's used on 12V.

Here is a fridge fuse connection I took out of a Burstner earlier this year ....

Blade Fuse Holder by David, on Flickr

Replaced it with a Midi Fuse & Holder....

Also there are multiple conversations you can find regarding fuse connections overheating on Sargent EM40 (or EM50?) Distribution units and EBL Fridge connectors.

 

[GeoffL]

I suspect this is something that can happen as the fuse/holder age and corrosion builds up on the blades and socket. My van had the same issue and the fridge kept blowing fuses -- I suspect that the heat generated by resistance added to the heating effect of the fuse itself was enough to blow the fuse. Thankfully, the fuse is contained in a 4-way unit bolted to the battery tray and fitting a new one was an hours work with the part costing just a few quid.

 

[gasgas]

I need to go and order a midi fuse holder. I had noticed my fridge fuse getting warm, but no damage done. This melting could happen if the fuse is not inserted correctly between the female pins. Some fuse holders allow the fuse to be inserted with the blade offset to one side of the holder, only touching the female parts on one side of the fuse blade.

One way to limit the current flow to the fridge would be what Ford did in the 1970's. They used 10v HT coils, with two feed wires. One was copper, from the starter position on the ignition switch so as to put the whole battery voltage on to the 10v coil. That makes sense. The other wire was a resistive wire which was powered by the engine battery when the engine was running. So the coil still got 10v, the resistive wire dropping the alternator voltage. Saved - oooh --- possibly 2d on the cost of each coil in reduced copper windings, and also saved some d as carbonated string is cheaper than copper wire. They also used carbonated string for HT leads. After a while the carbon would separate out into islands, causing multiple gaps for the spark to jump across on its way to the plug.

 

[runnach]

An important point David made which I would never have thought about is, fuse blade thickness, I mic'd mine and they all came in at .6 of a millimetre (0.0236). Also fuse quality eg: my pic where you can clearly make out the fuse rating, as it is painted on, a sign of a quality fuse. While the other fuses are marked of course, but not as clearly as the paint rated type. I've also experienced fitting a new cheap fuse to find bends or gets disfigured easily when installing. I usually but the cheapo amazon type, I'll be buying spares from RS from now on.

 

[wildebus]

For Blade Fuses, I think I would be perfectly happy with these variety pack - https://amzn.to/3YC8cv1 - 40 Fuses for £30
Littelfuse is a pukka brand, well respected and reliable (and actually is the company that created the ATO (Standard Blade) Fuse.)
RS Online sell a different Littelfuse selection box - https://uk.rs-online.com/web/p/fuse-kits/2199556 - 100 Fuses for £51, which is pretty decent for top quality fuses.
The Amazon set is more cost per fuse, but will you ever need more than what is in that box of 40? I would say a box of either of those would likely be the last box of Spade/ATO fuses you will ever need to buy.

I've also experienced fitting a new cheap fuse to find bends or gets disfigured easily when installing. I usually but the cheapo amazon type, I'll be buying spares from RS from now on.

A fuse bending over when pushed in a bit askew is for sure a sign of a cheap fuse. I've also had that a few times.
I've got lots of cheap fuses as you get bags of them included with fuse boxes and I do keep them as they basically do the job - but I wouldn't use them for a circuit that is live for hours or something important

 

[gasgas]

An important point David made which I would never have thought about is, fuse blade thickness, I mic'd mine and they all came in at .6 of a millimetre (0.0236). Also fuse quality eg: my pic where you can clearly make out the fuse rating, as it is painted on, a sign of a quality fuse. While the other fuses are marked of course, but not as clearly as the paint rated type. I've also experienced fitting a new cheap fuse to find bends or gets disfigured easily when installing. I usually but the cheapo amazon type, I'll be buying spares from RS from now on.

You are dead right about the blade thicknesses, I have got some really bent ones, made of such thin metal that they can hardly stand the strain of being pushed into their sockets without bending. The same applies to car fuses. OK I know the regular blade fuses in hab areas of motorhomes is usually the same as car ones - except the tiny miniature ones that are current. I have a 40 year old car which uses torpedo fuses. The original German ones had ceramic bodies and copper conductors but over the years some have been replaced with modern plastic bodies and aluminium conductors. Some of these have melted, just wilted with current, not blown. and the aluminium conductors have reacted with the copper fuse holder ends, oxidising their way through the aluminium and going open circuit. I tried ordering on line ceramic bodies with copper conductors and what came was not ceramic though it was some sort of hard plastic, and the copper was in fact brass. Still better than plastic and aluminium though.

Another electrical thing to look out for is did you know that crimp type blade wire connectors come in at least two qualities? I was at a motorhome open air show in Spring and was attracted to one of those tool stalls, you know, like Pooh bear to a hunny pot. I saw that on the trays of blade wire crimp connectors they had a notice saying connectors to BS something or other, I can't find it now. What that means is that a quality crimp connector will be made to a British Standard (or I presume European Norm EN) from two separate stampings of tin plated copper. One stamping is the blade part you can see but there is another. If you look down the barrel from the wire-insertion end you will see two circles of metal - an outer one and another one concentric inside it. This is the grippy part as shown in this diagram:
https://www.farnell.com/datasheets/3762874.pdf. These connectors are far superior to the cheap tat you get otherwise.
By the way in case you didn't know Farnell is good quality, as is RS components.
The bottom line is that if you want quality connectors - which might cost twice as much as rubbish ones that don't work, take a look down the wire-insertion end and see if you can see two separate circles of metal. In any case they are all cheap, so twice not much is still cheap compared to the things you are connecting. And once you have crimped (I have a Raychem racheting crimper) give the wire a tug to check it is secured properly.