Dead giveaway for fuse box problems

Bill Crowell

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I have several older Mopars with the old-fashioned glass fuses, and they all eventually developed anomalies in various circuits due to poor connections in the fuse box. At first these issues can be difficult to troubleshoot because you might not find any open circuits with an ohmmeter, but when you start to load the circuit down it just won't conduct current. The dead giveaway that you've got fuse box problems is when you start blowing fuses, but when you connect an ammeter in the circuit you find it is not drawing excessive current. The reason the fuse is blowing is due to heat at the end of the fuse that has the poor connection melting the fuse element at that end, vs. when a fuse blows due to excessive current draw it will almost always melt the middle of the fuse element.
 

KitCarlson

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A thermal camera or temperature gun can be used to identify problems like that. Temperature guns are inexpensive, but may require stick-on black targets to get around emissivity errors.

The original fuse box contacts are often corroded steel, with original tin or cadmium plating gone. I think there might be replacement contacts available, seems like early Mustangs used similar.

I have considered designing a replacement PCB, with heavy copper traces, copper buses, and sockets for modern blade fuses. There could be other improved features, including relays. Right now many irons in the fire.
 

KitCarlson

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The fuse contacts are often corroded steel after the plating goes away.

I have considered designing a heavy PCB, with copper busbars, and modern blade fuse sockets. Real busy right now, so might be a year or two.
 

Rapid Robert

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The fuse contacts are often corroded steel after the plating goes away.

I have considered designing a heavy PCB, with copper busbars, and modern blade fuse sockets. Real busy right now, so might be a year or two.
best tool for cleaning the fuse box metal "saddles" that the glass fuses sit in is a HF $9.95 dremel. Only has a small amt of torque but is perfect for this. Are there a brand of glass fuses that are top quality?
 

Bill Crowell

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Yes, those OE-type fuse clips are NLA and are now as scarce as hen's teeth. Never did find an exact replacement from any of the electronics suppliers, from McMaster-Carr or similar sites. I have a few NOS ones that I have hidden away so I won't use them unless really I need to, and always try to refurbish the old ones instead.

Of course you can easily remove the fuse clips from the fuse box in order to clean them. If the fuse box has a burned out spot, you'll have to either get a new one or glue the fuse clip in with plastic epoxy.

I've had good luck cleaning the old fuse clips with acetone, filing off any rust or corrosion and installing the fuse with a tiny dab of silver conducting paste on its ends. Besides being a super good conductor, the silver conducting paste also greatly increases the contact area between the fuse and the clip and assures a low-resistance connection.
 

69conv

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That silver conducting paste sounds interesting. Where can I get some?
 

Bill Crowell

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That silver conducting paste sounds interesting. Where can I get some?

Here you go:
Amazon.com: mg chemicals silver conductive grease

All of the electrical circuits on my old Mopars seem to work so much better now that I am using silver conductive grease on the fuses and on the spade connectors that attach to the fuse box. Also, the fuse box power feed buss bar should be soldered to the power feed spade connectors (leave the rivets in place and just solder on each side of them). Basically, solder all the riveted connections in the fuse box using rosin core (electronic-type) solder.
 

Rapid Robert

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What kind of a bit do you use on the dremel to clean the saddles?

Thanks!
I used one of the ones in the kit but I dont remember exactly which one as its been 5 yrs+ since I did it. what I would do is start with the smoothest/softest one in the kit & work up from there. it gave a bright bare metal finish with no gouging/metal removal. cant go wrong for the price. RR
 

toolmanmike

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Dielectric grease should prevent further corrosion once the fuses and terminals are cleaned up. A small wire brush on a Dremel works well on those terminals like RR mentioned.
 

halifaxhops

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Mike remember dielectric greas is not conductive. Great for keeping corriosion at bay and thin enough so when you put a connector together it makes contact.
 

toolmanmike

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Mike remember dielectric greas is not conductive. Great for keeping corriosion at bay and thin enough so when you put a connector together it makes contact.
Thanks teacher. I didn't know that.
 

Dfr360cuda

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No Ox
Use this

A39CA645-0E3C-4A22-9935-2225441BF154.jpeg
 

jos51700

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This is why I don't add ANYTHING to an OEM circuit on my cars. Ancillary fusebox with modern blade fuses run off a tap somewhere under the hood.
I'm also in favor of replacing certain bulbs with LED's if I can find LED's that are broadcast and not cheap ****.
 
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