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Old 01-31-2019, 10:01 PM   #1
dfrenc2
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72 super Cheyenne 402, blowing fuseable link/fuse when cranking

I have a 72 Chevy 402 hei. fuseable link replaced with fuses.
i went to crank my truck the starter turned my engine over but did not crank it, at the same time my main fuse blew and my alternator belt broke.
I have installed a new starter harness, ignition switch.
Checked wires for ground with no luck.
so far with starter wired up it blows fuses only when key is turned to ignition only... I am stuck
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Old 02-01-2019, 03:42 AM   #2
VetteVet
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

If you are blowing fuses only when you turn on the ignition it means that you have a short to ground somewhere past the ignition switch and all of your key off powered circuits are ok. The key switch powers the fuse panel, the accessories, the external regulator, the turn signals, the distributor Bat terminal,the gauge cluster, the radio, and anything else that needs key on power.

Can you detail which fuses you are blowing? those would be the circuits that are grounding. In order to trouble shoot this problem you need to know the path of the electricity from the key switch to the various switches and circuits that only work with the key on.

Do you have a multi-meter? If so then disconnect the positive battery cable and connect the meter red lead to the IGN Unfused terminal on the fuse panel and the black lead to the best ground you can find near there. You want the meter on the continuity (resistance) setting. Make sure all the fuses are good and have good contact in there holders. Make sure that all the switches are off. Heater, wipers, radio.

I would start with the external regulator plug because the key feeds the brown wire that goes there.
Turn on the key and look for a reading on the meter close to zero. You should get that if you are blowing fuses when you turn on the key. If you do.

Unplug the regulator plug. Did the reading go up? Yes, No

If no, turn on all the switches then pull the fuse for that switch and read the meter. Leave that switch on and the fuse out as you go to the next one. Be sure to take not of where the fuses go. If you don't have any additional things wire into the key switch you should be able to figure out which circuit is grounded and then you can look for bare wires or wires touching a ground.

It would take a pretty good short to blow a fusible link and I would expect to see some burnt insulation on the shorted wires.

Here is a picture of the fuse panel with the key on hot fuses and the key off hot circuits to help you. Courtesy of DJLambert.


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Old 02-01-2019, 12:00 PM   #3
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

the fuseable link was replaced with two separate fuses. those fuses are the only one blowing and only when I have the starter wired up.
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Old 02-02-2019, 01:52 AM   #4
VetteVet
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

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Originally Posted by dfrenc2 View Post
the fuseable link was replaced with two separate fuses. those fuses are the only one blowing and only when I have the starter wired up.
This doesn't add up. There are only three wires going to the starter. The large cable, the purple solenoid wire and the small resistor bypass wire on the outside terminal of the solenoid.
The large cable is key off hot so it would blow the fuses as soon as it was connected with the key off.

The purple solenoid wire wouldn't blow until the key was turned to the cranking position.

That only leaves the small black and yellow R wire which is connected to the key switch and the ignition coil. It is powered as soon as the key is turned on to ignition. If you have this wire, and you should, unless you have an HEI distributor, then it is possible that the terminal where it is connected to the starter solenoid is shorted to ground, and when the key is on it would blow the fuses.

This terminal (R) is powered internally inside the solenoid to send 12 volts to the coil while the starter is cranking. If it is grounded inside the solenoid then it will burn up the solenoid if the wire is left off and the starter is energized.

I suspect that the terminal has turned while attaching the wire and it is touching the solenoid housing.

There is a reason the fusible link is used instead of the regular type fuses. A fusible will allow for a larger amperage draw before it blows, such as when a surge happens in the battery power circuit like when the accessories are turned on or when the lights and brake lights are applied at the same time.
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Old 02-02-2019, 11:30 AM   #5
vince1
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

Just a question about the belt. Was it rotten or is there a component not turning?
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Old 02-04-2019, 08:28 PM   #6
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

to start off. I think I had a bad starter from the beginning. I replace starter and it quit blowing the "fuse that replace the fuseable link".

so I am going to delete thread.before I do though.

but In trying to find a grounded wire I ground the purple and yellow wires going to the starter. and burned my instrument cluster printed circuit.

so my question is. since I burned the cluster circuit I am not getting voltage to anything ( fuse box, yellow wire at starter, no lights etc)

would burning that prevent me from getting voltage to the fuse box?
can you give me some where to start?
thanks vette
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Old 02-07-2019, 07:51 PM   #7
kwmech
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

Um yeah, stop grounding power wires. Where is this fusible link wire you replaced with fuses? Give us pics----- With the HEI the yellow wire at the starter should have been removed from the harness all the way to the bulk head at the firewall. At the bulkhead you should have replaced the yellow wire with a direct wire to the HEI cap...(preferably at least) a 14g pink. Leave the dash out at this point, replace the fuses where the fuselink is, completely unplug the alt.

Starter: batt cable to large terminal, purple wire to S (S terminal is closest to block with the starter installed). Yellow wire removed as previously stated.

Hook up battery and turn key on fuses blow, report back here.
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Old 02-14-2019, 07:45 PM   #8
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

bought new wiring harness for engine compartment with hei and internal regulator altenator. I installed the starter side.
now I'm installing altenator side. the black and the black/ white have this connection but a regular glass fuse doesn't fit, and what size should I use?

Last edited by dfrenc2; 02-14-2019 at 07:48 PM. Reason: pictures
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Old 02-14-2019, 07:51 PM   #9
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

this is the black wire ran to the battery side
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Old 02-14-2019, 10:06 PM   #10
ray_mcavoy
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

Those holders are for the fuses that protect the battery gauge circuit. They take SFE-4 fuses.
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Old 02-14-2019, 10:07 PM   #11
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

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Originally Posted by ray_mcavoy View Post
Those holders are for the fuses that protect the battery gauge circuit. They take SFE-4 fuses.

thanks.
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Old 02-15-2019, 07:36 PM   #12
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

the side market light was replaced with led. wiring harness has plug what are yalls suggestions?
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Old 02-15-2019, 07:56 PM   #13
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

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Originally Posted by dfrenc2 View Post
the side market light was replaced with led. wiring harness has plug what are yalls suggestions?
You might want to try something like these --> https://www.ebay.com/itm/Wire-Harnes...pid=1991139562

Once you splice something like those onto the LED side markers, you should then be able to plug them right into the bulb sockets on the wiring harness.
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Old 02-16-2019, 08:19 PM   #14
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

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Originally Posted by ray_mcavoy View Post
Those holders are for the fuses that protect the battery gauge circuit. They take SFE-4 fuses.

man they are small. thanks for the info. got them in today and I should get light plugs monday.
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Old 02-18-2019, 04:56 PM   #15
dfrenc2
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

the starter side of wiring harness. blue is oil pressure? green is coolant temp. what I'd the extra pink. the other pink is going to hei distributor
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Old 02-18-2019, 07:37 PM   #16
ray_mcavoy
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

I think that other pink wire is for an idle solenoid that was used on some carburetors.
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Old 02-18-2019, 07:39 PM   #17
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Re: 72 super Cheyenne 402, blowing fuseable link/fuse when cranking

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Originally Posted by ray_mcavoy View Post
I think that other pink wire is for an idle solenoid that was used on some carburetors.
ok. thanks
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