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fuse blows....sometimes

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Old Feb 6, 2011 | 09:42 AM
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fuse blows....sometimes

15 amp fuse#21 inside cab blows.... sometimes, not with the key on,...only when starting. will start 4-5 times ok then will blow?

starter was rebuilt when this first happened.

could this be the starter relay?

or the ignition switch?

any other ideas?

where should i test first

thanks roscoewalsh2010@gmail.com
 
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Old Feb 6, 2011 | 10:11 AM
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Sure sounds like the starter relay.
#21 15amp; Clutch pedal position switch, Starter interrupt relay.

BTW Welcome to FTE!
 
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Old Feb 6, 2011 | 12:44 PM
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F21 is hot ONLY when cranking. It would be extremely long odds that the starter relay is causing the intermittent short A wiring harness is a far more likely problem. The starter motor itself cannot cause this problem.

Have you had any exhaust or transmission work done? The harness for this circuit is easy to damage when doing this type of work. Otherwise, in might be damaged due to chafing or rubbing.

It is necessary to identify your vehicle including year, model, engine, and transmission since there are considerable variations between the different versions. Also, identify if any aftermarket alarms or security systems are installed.
 
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Old Feb 6, 2011 | 01:18 PM
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Originally Posted by roscoewalsh
15 amp fuse#21 inside cab blows.... sometimes, not with the key on,...only when starting. will start 4-5 times ok then will blow?
Again I suggest that the relay be checked as the source of the problem. It may be pulling too much power.
 
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Old Feb 6, 2011 | 08:27 PM
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I've been fixing electrical and electronic equipment for 35 years. Can't recall ever having a relay with a shorted coil.
 
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