topfuel67

I have a 93 Jeep Cherokee Sport 4.0l, 5 spd 2wd, 4 door. I have replaced the blower motor, blower switch and the resistor under the glove box. Ac works great. The 25 amp fuse keeps heating up to the point where it is melted and black (but doesn't blow). The aux fan is supposed to always kick on if the ac is on. It doesn't. So I wired that directly to a fused toggle switch on my dash.
So my question is what should I start checking to see why my fuse is over heating. Is it just old wire not up to the task of running my ac? I'm in so Cal and run my ac on full just about year round.
Any suggestions are appreciated.

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Griffyorcono

From another thread about this but different problem "Hello, I'll try to help, first get your service info and find out what is connected to that circuit. when the fuse blows that means excessive current flow ie. short to ground(frame chasis etc.) if you take a test light or headlamp bulb and connect it to the terminals of the fuse cavity (while it is shorted) the bulb will light. Then you can start disconnecting components untill the light goes out. when the light goes out you have found your problem."

wingless

Welcome to the forum.

My speculation is that the fuse blades are not making a good connection into the fuse block receptacle.

If that fault exists, then what should be a very low resistance connection instead has a higher resistance, causing a voltage drop at that point during the high current normal operation.

That voltage drop and high current results in heat at that spot, causing the melting.

It should be possible to disassemble, inspect, measure and clean that connection, after first properly disconnecting the battery negative terminal.

topfuel67

Thank you for the replies. The fuse is really loose in there now as it has been making it worse and worse as this keeps happening. I'll start off with trying to replace the contact in that spot as they are now brittle and missing metal.
I just want to be sure that if I replace that it's not just going to fry another set.

dave1123

When a fuseholder melts but doesn't blow the fuse, that's a sure sign of high resistance at the fuse contacts. If this fuse is in the underhood fusebox, you should replace it with a remote fuseholder external to the fusebox. You should buy one with a flip cover and heavier wires.