Backup/turn signal fuse melting in reverse 2004 Itasca Suncruiser

[hroth7]

Has anyone had a problem with the backup/turn signal fuse overheating, to the point of melting, in reverse only, in a 2004 Itasca Suncruiser ? Please advise.

 

[Morich]

Morning folks! Isn't this sort of thing fun? AARGH!
So I feel for you and might start the discussion!
First we can do better if we get a few more facts, some about the RV and some about the problem. That year and model come in lots of different sizes and different builders for the chassis/truck part it rides on!
Can you tell us which RV model ? That can often lead us to the correct drawings to sort which way the wires go!

Then some more details, like which chassis builder, as I am seeing some on Ford while others are GM and this will have a lot of the questions on things built by the chassis folks. If we can get down to the right one before we start it can save lots of bad guessing!
Then it sounds odd that one fuse is blowing as those are two different circuits on what I have looked at. Guessing says it should be either a backup light fuse or a turn signal fuse, so any details you can add there may help?
Just starter guesses, I might think there is a problem on the trailer light connections but that is just because they hang out in the weather and tend to get beat up more! Does this happen when a car is connected or without?

 

[Waterbug]

If a fuse or fuse holder is melting, without the fuse blowing, someone has probably replaced a blown fuse with one of higher value, or the contacts are badly corroded.

 

[Morich]

Yes, that would certainly be a different thing all together, if the fuse holder is melting. I had read it as the fuse melting, but that is where this communications stuff gets hard!
If it is the fuse holder melting down, that might make it much easire to sort the problem but harder to fix. If it is the fuse itself melting, we have to look harder but likely easier to repair once found?
But that is where we need more info to avoid the guessing! But to keep the conversaiton going, my first guess would be a short at teh trailer connection on the rear of the RV and for a couple reasons. Assuming it only the fuse has melted/blown/tripped or however we describe it, there is likely to be a short in the wiring between one or more hot wires and ground. That means current that should have to go out to some light and baack to ground can take a short cut (short?) to ground. Without having to do the hard work of going through the resistance of the light bulb, it can just flow easily to ground. That easy path makes much more current flow to overheat the element in the fuse for it to melt down.
One common place for this to happen is the trailer connection as it is exposed to lots more abuse than the things inside out of the weather where they also don't get knocked around as often for physical damage.
Seems kind of easy to back the RV into something in the campground and not notice we mashed the wires on the connector hanging down underneath the rear bumper!
But that is just filling space until we get more info and specifics on what has happened to what!

 

[hroth7]

Morning folks! Isn't this sort of thing fun? AARGH!
So I feel for you and might start the discussion!
First we can do better if we get a few more facts, some about the RV and some about the problem. That year and model come in lots of different sizes and different builders for the chassis/truck part it rides on!
Can you tell us which RV model ? That can often lead us to the correct drawings to sort which way the wires go!
View attachment 2517620
Then some more details, like which chassis builder, as I am seeing some on Ford while others are GM and this will have a lot of the questions on things built by the chassis folks. If we can get down to the right one before we start it can save lots of bad guessing!
Then it sounds odd that one fuse is blowing as those are two different circuits on what I have looked at. Guessing says it should be either a backup light fuse or a turn signal fuse, so any details you can add there may help?
Just starter guesses, I might think there is a problem on the trailer light connections but that is just because they hang out in the weather and tend to get beat up more! Does this happen when a car is connected or without?

It's the ifg33y with a workhorse chassis. The fuse is getting so hot it actually begins to melt. It's the fuse labeled as bu/turn signal. It's a 15 amp mini fuse which is what's called for in that slot. It only does this when the transmission is placed in reverse. The fuse never blows but will melt.

 

[bigbAZ]

It's the ifg33y with a workhorse chassis. The fuse is getting so hot it actually begins to melt. It's the fuse labeled as bu/turn signal. It's a 15 amp mini fuse which is what's called for in that slot. It only does this when the transmission is placed in reverse. The fuse never blows but will melt.

Does it get hot immediately or are the reverse lights being used for an extended period of time?

 

[hroth7]

It gets hot within seconds

 

[Morich]

Not finding anything to help but I might suggest looking for physical damage to the main cable to the fuse panel. Something like rodent damage from chewing?
Is this only a problem when in reverse and turn signal used?
At this point, if the fuse holder is melting, it would seem too much damage for simple things like mashed wires further on out.

 

[bigbAZ]

As mentioned earlier it could be weak contact points in the fuse holder, which only get worse when subjected to heat. I would also check the reverse lamps to see if they have been upgraded to a higher wattage which could push the circuit close to it's limits.

 

[Morich]

For any specs on what was built, my first step would be to find out which RV it is as the info we have so far is not in anything I find!
But I would not expect that fuse panel to be on the Winnebago drawings but chassis drawings from Workhorse.

 

[klook]

I would guess the backup lights are an upgrade or there is a dead short in one of the factory ones.

 

[bigbAZ]

Doesn't really sound like a dead short as the fuse isn't blowing if I understand the facts given so far.

 

[klook]

So, what condition would cause a fuse to melt not blow? That defies logic. I had a 30 amp fuse on the tongue of my own camper melt the holder once. I felt it was the holder was shorted out inside. Hence a dead short in that location.

 

[bigbAZ]

So, what condition would cause a fuse to melt not blow? That defies logic. I had a 30 amp fuse on the tongue of my own camper melt the holder once. I felt it was the holder was shorted out inside. Hence a dead short in that location.

In the AC world we see it when a circuit is repeatedly loaded to maximum rating, breakers will eventually melt before tripping, but it happens after repeated high loading which gradually degrades the connections at the load terminals and/or at the bus. My guess, with the facts given, is that the connection points have been degraded to the point that they are causing enough resistance to create a hot spot at the fuse.

If the circuit could be easily accessed on both sides and an inline fuse holder could be installed bypassing the fuse box this could tell a lot. If the new inline fuse does not get hot we'd know if the fuse box connection was the issue.

It would also be helpful if the OP could measure the current flow on the circuit, and measure voltage drop across the fuse, but we don't know if they have the equipment or skills to do that.

 

[Morich]

Have to agree that it is not as likely to be a high current flow as much as arcing. If there was high current through the fuse, it blows almost certainly. But if the arcing is at the end of the fuse where the power goes in, that can cause a lot of heat without needing extra current flowing. Same theory as what makes a welder work? It is the heat from the arc, more than the total amount of current flowing. It could have been from something as simple as a weak mechanical holder for the fuse. But at this point, if the fuse and holder are melted, that may need wired around or the big job of changing out the fuse block!
Any work done in that area that might have damaged things?
One way to create problems is when we let somebody work on our cars! I had a tow package installed and the dummy thought the lid of the fuse panel was a good place to screw a part down! I was lucky and he missed any of the really critical points but he did run a screw down through a little mini relay that made it tricky to get the lid off the fuses!