melting fuse but not blowing it!!!

[BoostedSUV]

Every once in a while the horn fuse which also controls the interior courtesy lights melts and you can smell burning plastic in the truck. The fuse doesn't blow and everything continues to work. Here's the problem, about 6 months ago I had to replace the fuse box and the entire wire harness behind the dash because that circuit caught on fire and burned everything up w/o blowing the fuse!!!! I thought this problem was fixed when I changed the harness but apparently not!! I don't want to have to go through this mess again I need help on what to look for. The battery doesn't get hot... Every 12volt accessory I added (sirius/gauges/subs etc runs off their own circuit not through the fuse box so I can almost eliminate them as a cause.. Please help... if this thing burns another wire harness there will be a typhoon for sale real cheap beacause I'm not fixing it!! thanks

 

[cdezzz]

Re: melting fuse but not blowing it!!!

to me it sounds like you have to big of a fuse in it

 

[BoostedSUV]

Re: melting fuse but not blowing it!!!

its the 20 amp that it calls for, that would be a logical guess. The crazy part is the interior lights aren't even on when it gets hot!

 

[jshu77]

Re: melting fuse but not blowing it!!!

I would hook a meter to your battery and see what kind of voltage it is reading at while your truck is running. The regulator in your alternator could be going out, letting your trucks accessories run above normal voltage, and pulling more power without pulling enough amps to pop your 20 amp fuse. I have seen it happen before. If your battery meters at 14 volt or below while running check that particular circuit by metering it at the fuse.

 

[BoostedSUV]

Re: melting fuse but not blowing it!!!

it has a newer alt in the truck and the volt gauge reads between 12 and 14 at all times. I will put a meter on that circuit see if it tells me anything.

 

[supersports10]

Re: melting fuse but not blowing it!!!

Please help... if this thing burns another wire harness there will be a typhoon for sale real cheap beacause I'm not fixing it!! thanks

how cheap???:lol:

also i would turn everything on in the truck, i mean everything!!!

then pull the fuse, and see what elese stops working.

i had a similar problem and it turned out to be the cig lighter socket was junk!!

got a used one from scrap yard and bam!! no more blown fuses.

 

[warmpancakes]

Re: melting fuse but not blowing it!!!

another sugestion go buy a good quality fuse I ran into the same problem on a saturn guy wa using cheap chinese fuses that didnt "break" when over loaded the would melt but the circut would stay complete lost my ass on that job

 

[4C FED]

Re: melting fuse but not blowing it!!!

My suggestion for the melting plastic/fuse panel:
It sounds like that the contacts for the horn/DM fuse box may not be making good contact with the fuse. This extra resistance provided by the bad connection will prevent the fuse from blowing because the excess current is used up in the bad connection at or very near the fuse leg, rather than in the fuse. This extra resistance will still allow everything to work normally except for the fuse.

We've had this happen in some of the AC distribution boxes we build & install in our systems. If someone doesn't strip back enough insulation from the line or low line and gets a large amount of insulation and only a small amount of wire under the wire clamp, eventually it will overheat without tripping the breaker & burn input wire. System still works, but over time the coneection begins to degrade until the insulation on the wires smokes.

You also need to figure out what is drawing so much current. Hookup a DVM to the battery so you can monitor current. There should only be milliamps being drawn for the ECM & the radio. If you've got more start disconnecting things one at a time (fuses, relays, etc.) until (hopefully) you see the current draw drop.

 

[cloneman315]

Re: melting fuse but not blowing it!!!

try bending the tabes on the fuse so it fits tight in the block,it can be a little lose and cause resistance and get hot,kinda when u put jumper cables on a car to jump another and they are not tight and they smoke

 

[BoostedSUV]

Re: melting fuse but not blowing it!!!

I did some more looking into things and found that the only thing I lose when I remove that fuse is horn/courtesy lights/cig lighter. I did have my iPod running of the cig lighter when this was happening.


More imporantly I have the wire to the electric fan relay plugged into the fuse box on the supply side of the of that fuse. I am thinking the elec fan is drawing too much from that circuit on the supply side which will melt the fuse but now blow it since it's circuit does not travel through the fuse. I could be way off... does that make sense?

 

[supersports10]

Re: melting fuse but not blowing it!!!

I did some more looking into things and found that the only thing I lose when I remove that fuse is horn/courtesy lights/cig lighter. I did have my iPod running of the cig lighter when this was happening.


More imporantly I have the wire to the electric fan relay plugged into the fuse box on the supply side of the of that fuse. I am thinking the elec fan is drawing too much from that circuit on the supply side which will melt the fuse but now blow it since it's circuit does not travel through the fuse. I could be way off... does that make sense?

bingo!!!............ remove the fan from the supply side. find a fuse socket that is supposed to have a higher amp rating and use that.

 

[Loeryder]

Re: melting fuse but not blowing it!!!

elec fans pull a lot of current at startup and should be wired to the battery with a relay.

If you are sourcing the power for your fan from the oem fusebox then I would be willing to bet that is why you have stuff melting.

My elec fan has a hot fused line to the + batt terminal and a relay that is tripped from teh IC pump wire.
Nothing is tapped into the box.

I have my alky pump tapped into the power taps marked bat and never had any issues on that one.

 

[BoostedSUV]

Re: melting fuse but not blowing it!!!

Cool, after some further looking around that is what I discovered.The fan's power is fed right off the battery, but the ign. wire to turn it on/off was plugged into that circuit. I will try moving it to a 30amp circuit or maybe to the IC pump harness. That's a good idea, the IC pump is long gone but the harness is still right below the radiator!! excellent thinking!. Thanks all....

 

[Loeryder]

Re: melting fuse but not blowing it!!!

Cool thing about that is you can use the IC pump tables to turn your fans on and off.
Works Fn awesome!

Sounds like you are on the right track!

 

[TY0618]

Re: melting fuse but not blowing it!!!

I had the same problem with one of my Blazers.What it was in my case was the cigarette lighter. I never use the thing, than one day a friend plugged in her cell phone. The next day I started having problems, no horn, no rear relese, and the fuse would "pop". I unplugged the cigerette lighter socket, drove the truck for a couple of weeks, and boom....FIXED! So I replaced the female end of the cigerette lighter. I found out now that I work at the dealership, its not uncommon for a small amount of corrosion to build up in the socket, and once disturbed, to have these problems. I hope it helps.

 

[MIGHTYMOUSE]

Re: melting fuse but not blowing it!!!

any melting fuses i've ever had were attributed to poor grounds

 

[BoostedSUV]

Re: melting fuse but not blowing it!!!

Thought I had this problem resolved by relocating the elec fan wire but apparently not!!!! Truck keeps melting the fuse but not blowing it... I even put a lower rated fuse in and it will not blow it, just melts the plastic. I have a multi meter and I want to read the amperage of that circuit but I don't know how to use it!! Any help??

 

[sly dvl]

Re: melting fuse but not blowing it!!!

Your meter is probably only capable of reading up to 10 amps so if your circuit is drawing in excess of that (and it sounds like it is) then you'll blow the fuse in your meter.
If it's a cheap meter, then it probably doesn't have a fuse and you'll smoke the meter, maybe.
Remove fuse - make sure meter is on the highest amperage scale (usually 10) - make sure the black lead is in the COM pocket and the red lead is in the 10AMP pocket.
Insert leads in place of fuse and read.

As mentioned in an earlier post MAKE SURE THE FUSE TERMINALS ARE TIGHT IN THE FUSE BLOCK and contacting the fuse blades correctly. I had the exact same issue on my wife's Jimmy with the brake lamp fuse. Not blown, but melted. - see pics

K

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[sly dvl]

Re: melting fuse but not blowing it!!!

:checkit:

My suggestion for the melting plastic/fuse panel:
It sounds like that the contacts for the horn/DM fuse box may not be making good contact with the fuse. This extra resistance provided by the bad connection will prevent the fuse from blowing because the excess current is used up in the bad connection at or very near the fuse leg, rather than in the fuse. This extra resistance will still allow everything to work normally except for the fuse.

X2

K

 

[BoostedSUV]

Re: melting fuse but not blowing it!!!

thats exactly what my fuses look like. i would agree with the lack of good contact but this is the second fuse panel I've had in the truck and the same thing is occuring at the same cicuit. The last fuse panel caught on fire and melted everything. I replaced it with a new fuse panel and wire harnes and the same thing is happening.... Its the fuse that controls the cig lighter, horn, courtesy lights, and rear hatch. I have really good Fluke multimeter but I don't know what settings to use to read the amperage of that circuit as i turn things on.