Inline fuse continues to blow fuses

[magg383]

Last month I posted that I was having ongoing issues w/ my 73 Challenger 30 AMP inline fuse that keeps popping after start up.

Well, I just replaced the engine wire harness w/ a new correct one since the old one was modified to fit my big block vs. original small block. I was hoping that was my issue, but unfortunately it blew that 30AMP fuse before the motor even started while turning over after install!!

It all started last yr. after hooking up a portable jump starter and then going straight out for a ride. I noticed the exhaust was backfiring when getting on it (was 2 bad plug wires), headlights were flickering, whining noise coming from behind firewall and gauges were fluctuating

Next day I discovered the battery was dead and my head lights were burned out so I bought a new battery and headlights. (Halogen)
The back of the voltage regulator also had melted some of its rubber on to the firewall, so I replaced it.

A Mopar friend came over and discovered the fusible link next to the starter relay was fried and replaced it w/ a 30 AMP inline fuse.
He then discovered the wires at bulkhead#16(battery) and #18(Alt.) were fried and drilled them out and ran wires straight trough.
We then discovered the 2 field wires coming out of the Alt. were fused together up aways, so I repaired those 2 wires.

I have replaced all the engine side electrical components inc. alt.

I'm guessing there must be a dead short somewhere since the fuse is blowing.? But where? Wrapped wires under dash melted together?

I'm thinking about taking dash out and unwrapping the wires to inspect the wire harness, but that has to be a tedious job.
Or just buying a new one.
But then again, I don't know if this is the issue or not and don't want to spend extra $ if not needed.

So anyways, I was hoping to get advice on how to diagnose why this fuse keeps blowing. Thanks for any feedback!!

Side Notes:
Replaced burnt out headlights W/ Halogen last yr. (does using Halogens affect anything?)
Battery is good and does not discharge
Alt. does charge battery while driving
Pos. battery/starter cable looks ok, bolts on starter studs are tight (read that only reason for main fusible link blowing is a short to ground on the + battery cable to starter.)??
floor dimmer switch 3 wires look good coming out of it
Do not use my rear defog, headlights, fan, and no P/windows and radio is detached
I have read that a battery and a starter can be shorted out.?
3 months ago, I went on 4 separate trips before it popped, always while cranking the motor over when it pops.
When it pops while running, the tach fluctuates all over
Non-AC car w/ 60 Amp Alt.

 

[Chryco Psycho]

I will have more time to consider this in the next couple of days , too busy right now .

 

[MoparCarGuy]

Wow, you have spent a lot of time and $. Troubleshooting this requires isolating using the "divide and conquer" method.
Buying more wiring harnesses or spending more $ may solve the issue but systematic troubleshooting will definitely find the culprit. An intermittent problem is the most difficult to find.
It would take a lot of posts and testing to find your problem. I recommend getting someone to assist who knows Basic Electricity and automotive wiring.

 

[Challenger RTA]

30 AMP inline fuse that keeps popping after start up. That's a start. That gives a place to look. 30 AMP is what is need to protect the wiring. To put a smaller fuse in place for now while trouble shooting or a circuit breaker would not hurt.

 

[Challenger RTA]

Well, I just replaced the engine wire harness w/ a new correct one since the old one was modified to fit my big block vs. original small block.

That is the correct thing to do correctly, 73 did not come with a big block. The bulkhead pin out has to be looked at to see if it is all correct. Some wiring is different depending on year make and California spec.

 

[Challenger RTA]

It all started last yr. after hooking up a portable jump starter

That's A question. How big of a jump starter? 250 AMP?

backfiring when getting on it

Years back and even now If a voltage regulator is going bad. Most of the time when shifting and or accelerating or de accelerating there will be a back fire.

gauges were fluctuating

The now could be a problem with the gauge cluster voltage limiter.

 

[Challenger RTA]

A Mopar friend came over and discovered the fusible link next to the starter relay was fried and replaced it w/ a 30 AMP inline fuse.
He then discovered the wires at bulkhead#16(battery) and #18(Alt.) were fried and drilled them out and ran wires straight trough.
We then discovered the 2 field wires coming out of the Alt. were fused together up aways, so I repaired those 2 wires.

That is the weak point of the system. But it might have melted wires beside those two already.

 

[Challenger RTA]

There is power to the alt when ever the battery is hooked up. Yes with sw off. Ign sw feeds power to Acc side of fuse box.
The heavy wire is on the ALT stud, that come from the battery. Touch that with the test light and clamp to ground. same for the ACC and Batt on the fuse box. The tester can be use ether way. Clamp or test prob to ground. unless it's a led some have polarity.

 

[Challenger RTA]

1:RED wire 16 Battery power yellow dot to splice one feeds fuse block, 2:charge wire 18 black wire blue dots to splice one through amp meter to red wire blue dot 16 to battery, 3:ACC feed from splice 1 Red wire Q3_12R yellow dot to steering column. Black wire 12BK red dot to ACC side of fuse box.
Start with a test light on battery to ground. 1 Check to see if you have power at starter relay. 2 unplug bulkhead connector check Red 12 ga wire for power. 3 check fuses box terminal marked BATT for power. 4 Under the steering column unplug connector and check the Red 12 wire. This should always be hot when the battery is connected. The alternator feed will also be hot R6 12 bk.

 

[Challenger RTA]

This is splice 1 untapped . where everything is tied together. Loads Headlight, ALT, AMP meter and ign sw power. See the brown wire beside it that is for ign. It is probably melted too. Just a guess because you said the fuse blows when starting.

Here's the brown wire again.

 

[Challenger RTA]

Unplug the the ign sw plug under the column and hot wire it to see what happens. Might be an ing sw, at least it will narrow it down.

 

[magg383]

There is power to the alt when ever the battery is hooked up. Yes with sw off. Ign sw feeds power to Acc side of fuse box.
The heavy wire is on the ALT stud, that come from the battery. Touch that with the test light and clamp to ground. same for the ACC and Batt on the fuse box. The tester can be use ether way. Clamp or test prob to ground. unless it's a led some have polarity.

Test light comes ON when attached to Alt. stud (what does this suggest)?

Test light comes ON when attached to Batt on fuse box (what does this suggest)?
Test light does NOT come on when attached to ACC on fuse box (what does this suggest)?

 

[Challenger RTA]

Test light comes ON when attached to Alt. stud (what does this suggest)?

Means there is a a connection from the battery to the alt. It might not be perfect but it is there as it should be.

 

[Challenger RTA]

Test light comes ON when attached to Batt on fuse box (what does this suggest)?

There again same as above.

 

[Challenger RTA]

Test light does NOT come on when attached to ACC on fuse box (what does this suggest)?

Did you turn ing sw on when testing ACC.
There should be power when ing sw is on.
If not you might also have a bad ing sw or the plug under the column has a bad connection.

 

[Challenger RTA]

You were responding in a few minutes. I'm going to guess the fuse is blowing when you turn the sw on or your out of fuses. 1 thing to do is unplug all the bulkhead connectors except the one from the battery the middle one and turn the sw on see if it blows.
I know this is a shotgun approach but it will narrow it down inside or outside.

 

[magg383]

Did you turn ing sw on when testing ACC.
There should be power when ing sw is on.
If not you might also have a bad ing sw or the plug under the column has a bad connection.

Retested Acc w/ ign. sw. on.
Test light does come on
What does this suggest?

 

[Challenger RTA]

Retested Acc w/ ign. sw. on.
Test light does come on
What does this suggest?

It is working correctly. The fuse didn't blow?

 

[magg383]

You were responding in a few minutes. I'm going to guess the fuse is blowing when you turn the sw on or your out of fuses. 1 thing to do is unplug all the bulkhead connectors except the one from the battery and turn the sw on see if it blows.
I know this is a shotgun approach but it will narrow it down inside or outside.

The fuse does NOT blow when I turn on the ign. switch itself.
It seems to blow only while turning the motor over.
2 months ago, I made about 4 separate trips before it blew that fuse
Do you still want me to unplug the other 2 bulkhead connections beings that the fuse does not pop when ign. switch is turned to the on position itself?

 

[Challenger RTA]

1 thing to do is unplug all the bulkhead connectors except the one from the battery the middle one and turn the sw on and to start see if it blows.
I know this is a shotgun approach but it will narrow it down inside or outside.

If it blows it is more than likely shorted somewhere in the dash harness. Like the pictures in post # 10