What causes this to melt? - PeachParts Mercedes-Benz Forum

nazrat · #1 12-11-2005, 06:56 PM

I have a spare fuse box that I need to swap in to fix the melting. The fan appears to be ok. It runs with 12V is applied and spins freely. Is there something hidden in that circuit?

Also, where can I find the glass fuses instead of the plastic/AL ones?

Thanks,
Tad

JamesDean · #2 12-11-2005, 07:09 PM

hmm those dont look like MB fuses...and uve got some dissimilar metal in there...Al and Cu....as to the melting...heat probably done it...could be that fuse....

MikeTangas · #3 12-11-2005, 07:20 PM

I 'm assuming that circuit is for the blower motor. If so you can do the external 30amp strip fuse upgrade. I believe someone recently posted a how to for the 123. Also assuming this is for the '84 not the '95.

Wasuchi · #4 12-11-2005, 07:21 PM

You need to get some of the ceramic fuses like are supposed to be in there, Fastlane is about the only place I know that has them.

nazrat · #5 12-11-2005, 07:43 PM

Can someone else confirm that that fuse location is the inside blower motor? I only have a book in German that covers the fuse locations and what I got out of it was that that fuse was for the aux fan in front of the radiator. Tell me that I am wrong and I'll be a happy camper installing the 30amp fuse retrofit.

-Tad

#6 12-11-2005, 07:55 PM

According to my wiring diagram, this fuse "C" is for the auxiliary fan, not the cabin blower.

Brad123D · #7 12-11-2005, 09:41 PM

Have you ever done any arc welding ? Arcing creates very high temperatures and can melt anything close to it like a plastic fuse box. You took a very good photo...looks to me like you need to take all of your fuses out and clean them and the contact points in the fuse box. I see green corrosion on the ends. Use fine sandpaper or something...but don't short anything out. Disconnect battery first for safety. After you clean that mess up

...put some oxide inhibiting compound on them and that should stop the arcing.

This has burnt down a lot of houses also.

nazrat · #8 12-11-2005, 09:50 PM

The battery is out right now, and I'm going to replace the entire fuse box with one from my donor. I'd really like to find more fuses like the clear glass ones in that photo. They (like the normal BUSS clear glass fuses) don't corrode.

Good call on the cause of the melting though. Corrosion can cause a high resistance connection there which can cause heat.

-Tad

JamesDean · #9 12-11-2005, 10:08 PM

IMO, you should use MB type ceramic fuses

The corrosion your seeing is from dissimmlar metals (Aluminium fuses (silver colored metal) and copper contacts) I had a few fuses that were made of Al in my fuse box they too were corroded but then i got that kit, cleaned the contact and put the copper ones ones in...i havent seen any corrosion to this day.

Kris

nazrat · #10 12-11-2005, 10:21 PM

I can get a replacement fuse box and get away from those silly fuses and switch to the ATO style fuses which I can find in a 7-11 if needed. I could also easily have the fuse box in a location that isn't behind the brake booster. I can add circuits at the same time if I wish. All for around $30 to $35 + shipping and 2 hours of my time to solder extensions onto the wires (if necessary). I already have to spend some time replacing this fuse box with the one from my parts vehicle, so 2 hours may or may not be a good estimate.

I'm liking the idea of having a blade-type fuse box on the driver's side inner fender. I would have to extend the wires to that position. I could mount it under the dash above the brake pedal without extending them it would seem.

I've never had a blade type fuse cause a problem because of its design. These fuses however seem to have numerous problem including locating replacements. Even with the proper fuses (which I've had in my previous 123s) they seem to have a tendency to not seat securely over long periods of time.

Maybe I'm crazy for even thinking about this.

-Tad

JimmyL · #11 12-11-2005, 10:38 PM

I have found the copper ceramic style fuses at Autozone, O'Rielly's, Pep-Boys, etc......
They are not hard to find, as several automakers use them.

dieseldiehard · #12 12-11-2005, 10:45 PM

Quote:

Originally Posted by nazrat

I can get a replacement fuse box and get away from those silly fuses and switch to the ATO style fuses which I can find in a 7-11 if needed. I could also easily have the fuse box in a location that isn't behind the brake booster. I can add circuits at the same time if I wish. All for around $30 to $35 + shipping and 2 hours of my time to solder extensions onto the wires (if necessary). I already have to spend some time replacing this fuse box with the one from my parts vehicle, so 2 hours may or may not be a good estimate.

I'm liking the idea of having a blade-type fuse box on the driver's side inner fender. I would have to extend the wires to that position. I could mount it under the dash above the brake pedal without extending them it would seem.

I've never had a blade type fuse cause a problem because of its design. These fuses however seem to have numerous problem including locating replacements. Even with the proper fuses (which I've had in my previous 123s) they seem to have a tendency to not seat securely over long periods of time.

Maybe I'm crazy for even thinking about this.

-Tad

I have a melted fuse on a 123 also its from the fan shorting when the brushes wear down, have you checked your fan (inside fan)? Thats what the retrofit was designed to do, prevent this kind of melting.
I would think replacing the fuse holder will take one a gruelling 4 hours. its the underdash work that is hard on the neck! A new fuseholder sold for fairly high price on eBay recently.

Brad123D · #13 12-11-2005, 11:57 PM

Quote:

Originally Posted by dieseldiehard

I have a melted fuse on a 123 also its from the fan shorting when the brushes wear down, .

If you had the proper size fuse installed and making good contact, why didn't the fuse blow instead of causing a meltdown ? I suspect your fan shorted and poor contact at the fuse was the actual cause...high amperage draw combined with a short and high resistance/arcing at the fuse and something is going to melt...the fuse holder. Can't prove it, but that's my opinion.

Brad123D · #14 12-12-2005, 12:24 AM

Quote:

Originally Posted by nazrat

I can get a replacement fuse box and get away from those silly fuses and switch to the ATO style fuses which I can find in a 7-11 if needed. I could also easily have the fuse box in a location that isn't behind the brake booster. I can add circuits at the same time if I wish. All for around $30 to $35 + shipping and 2 hours of my time to solder extensions onto the wires (if necessary). I already have to spend some time replacing this fuse box with the one from my parts vehicle, so 2 hours may or may not be a good estimate.

I'm liking the idea of having a blade-type fuse box on the driver's side inner fender. I would have to extend the wires to that position. I could mount it under the dash above the brake pedal without extending them it would seem.

I've never had a blade type fuse cause a problem because of its design. These fuses however seem to have numerous problem including locating replacements. Even with the proper fuses (which I've had in my previous 123s) they seem to have a tendency to not seat securely over long periods of time.

Maybe I'm crazy for even thinking about this.

-Tad

I agree that blade type fuses are generally trouble free, but your fuse box clearly showed neglect(needed cleaning) and as was well pointed out, electrolysis was not helping the situation. I would suggest that you change to the copper fuses, as was suggested, clean up the fuse holder you have and replace the meltdown with an inline blade type fuseholder for that circuit only. I've had several harnesses out of different vehicles over the years for repair and I think you will have way more than a two hour challenge changing to a blade type fuse block on a MB . To do a nice job, I think the dashpad etc. would need to come out. And again...OXIDE INHIBITING COMPOUND can prevent many problems !

I like your "can-do" attitude though.