Posted by Don Williams on Thursday, October 24, 2002 at 3:40PM :
In Reply to: 74 Dodge fan problem posted by Todd Wilson on Thursday, October 24, 2002 at 1:35PM :
Melted out fuse boxes is a common problem on trucks of that era. I have a 73 that I had to replace the fuse box in and had to change to one in-line fuse on a ciruit where the clips in the fuse box were corroded real bad. If the fuse clips are a loose on the fuse it can cause a voltage drop at that point and cause the heating you talked about. As far as the fan motor goes, if you can get your hands on a DC ammeter to check the actual draw it will let you know if it is actually drawing too much current.
All fuses have what is called a trip curve. Typically a 20 amp fuse should hold 20 amps all day long. It will blow faster as the amperage goes above 20 amps. It might hold a couple of minutes at say 23 amps. It might hold half that time at 26 amps. At 30 amps it might hold 3 seconds. A dead sort will cause almost instantaneous fuse failure. These aren't actual numbers from a spec sheet, just some I picked as somewhat typical.
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