72 Dart Swinger Fuse Blowing (New to Older Cars)

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jlhunsinger

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A quick history of the car:

Recently bought this car as my first "big boy toy" as a young adult. 1972 Dart Swinger that has a 440 (1973 if I read the casting number correctly). The entire time I have owned the car I have been keeping it in my dad's garage 90 miles away. I wanted to build up some trust in the car before I brought it to house since I have little to no room to work on it for the next couple of months. I usually make the trip twice a month to see the parents and have been tinkering with the car so my ability to respond with pictures is not going to be speedy.

The issue I'm having is with a 30A in-line fuse that leads right into the bulkhead connector. From my reading on these forums I'm guessing this is the main power source to the ammeter (is this a replacement for the factory fusible link?). The ammeter has never shown a reading so I assume a previous owner bypassed it. Haven't had the dash apart to verify. There is an aftermarket electric fuel pump, BeCool radiator with electric fans, and electric water pump. Additionally on the switch panel there is a fourth switch labeled alternator. I was told this is to disengage the alternator in case I wanted to take the car to the strip. The battery is located in the trunk of the car and is an optima yellow top.

The fuse started blowing consistently after about the third or fourth drive after I bought it. The car will start and drive fine. All accessories work until we switch the car off. At that point you can't get the accessories to come on, lights, dome light, gauge lights, nothing...blown fuse. It doesn't necessarily blow every time the car is started because I've made multiple trips on a fuse before it blows again, but seems to blow about 75% of the time if the car is started for carb tuning or driven.

My plan is to be able to take all pictures necessary next time I make the trip home so I can post here.

The first time I could tell the fuse blew was when I had the door open while we were tuning the carb. I noticed the dome light clicked off so we checked the fuse and it was blown. If I recall correctly, after the fuse was replaced I remember thinking the dome light never came back on.

I know the alternator has the main black wire and two field wires. I understand that one of these (green) goes to voltage regulator and the other to the starter switch. I just replaced the alternator because the battery kept losing charge but it makes sense now that it was never charging correctly.

Dad said the headlights get brighter if you increase the rpm.

Can anyone give me an idea of what I could do to narrow the problem down so that I can gather the necessary information next weekend when I visit? Thank you all in advance for your time! I'm looking forward to ironing out the kinks and really getting to enjoy the car this fall.
 
IF (and I say if) someone has replaced the fuse link with a 30A fuse, that is nowhere near large enough.

Start by going there and downloading the 72 shop manual for free (Thanks to AbodyJoe)

http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617

There's some more good info and additional manuals here

http://www.mymopar.com/index.php?pid=31

Unrelated to your question, but wander around in there for awhile, as well as the Master Tech Service Conference stuff

Last and possibly most important, read this article

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

which came from here

http://www.madelectrical.com/electrical-tech.shtml

Even if you do not do the ammeter bypass as in that article, it points out the pitfalls of these old girls. Most any connector is suspect, as well as switches themselves. In some cases the ammeter itself can give trouble.
 
Thanks 67Dart273! I've read many of your posts the last few days and you seem to be the go to expert in this area. I've read the madelectrical article and will investigate that area soon. Do you think the load from the aftermarket electrical accessories is just overheating the fuse? What is a safe size fuse to go up to without creating too much of a fire hazard?
 
67Dart273 said:
IF (and I say if) someone has replaced the fuse link with a 30A fuse, that is nowhere near large enough.

Start by going there and downloading the 72 shop manual for free (Thanks to AbodyJoe)

http://www.forabodiesonly.com/mopar/showthread.php?p=1970088617

There's some more good info and additional manuals here

http://www.mymopar.com/index.php?pid=31

Unrelated to your question, but wander around in there for awhile, as well as the Master Tech Service Conference stuff

Last and possibly most important, read this article

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

which came from here

http://www.madelectrical.com/electrical-tech.shtml

Even if you do not do the ammeter bypass as in that article, it points out the pitfalls of these old girls. Most any connector is suspect, as well as switches themselves. In some cases the ammeter itself can give trouble.
Click to expand...

Im using a 30 amp inline fuse in my demon and have had no issues...... Untill the voltage regulator went bad and she was overcharging almost up to 18-20 volts.
#-o
 
My 1980 Volare blew that main link once on a roadtrip. I made a quick repair downstream, and still on the highway, I stole a length of wire out of the choke circuit, folded it in half and parralel-spliced it in. Worked like that for a week or two until I spliced a 30a ATO fuse in there. Its been good for years. -Sounds like you have a somewhat more serious problem.You definitely want to fix that.
-In 40 years of living in the Mopar world, I only ever had one VR go bad,and it was a nearly new Mopar Performance constant-voltage type. Ive been running one out of my spare parts stuff ever since .Mine went to 20plus volts.
-As to your problem,you might check the back-up lite circuit.
 
71DodgeDemon340 said:
Im using a 30 amp inline fuse in my demon and have had no issues...... Untill the voltage regulator went bad and she was overcharging almost up to 18-20 volts.
#-o
Click to expand...

How did you diagnose the voltage regulator? Did it start blowing fuses or was there some other indication?

I'm stumped with where to start if it isn't the voltage regulator.
 
With the mods to the car, you are going to have to do some work to let everyone know how things are now wired up. For instance, where is the main lead from the battery connected into the front area of the car? To the starter relay's big terminal, or to the starter main lug with a jumper to the starter relay's big lug from there? This is important for anyone to be able to figure out where the current is flowing, and what part of that is flowing through the fuse.

Also, where the accessories are hooked up is important, for the same reason. (Do they tend to source the current from the alterntor, battery, a combination?)

And can you tell us where the fuse is located in the circuit? Look at the schematic diagram that you can download from www.mymopar.com, and see if you can ID where it is. This is very important to figure out. The fusible link goes from the starter relay big lug to the bulkhead connector.

Your fuse blows could be to several issues:
- Alternator over charging and output spikes
- Accessories (depends on how they are wired in)
- Harness shorts
- Erratic grounds casuing current to flow where it should not or voltage spikes

BTW, your post is a bit confusing.....does this tend to blow only when the car is turned off or at any time? One possible issue I can see from your description is that the +12v to the alternator's field is tied to the "starter switch". What is this "starter switch"? Can you find out how this is actually connected. This is normally fed from the IGN1 circuit off of the ignition switch so that the field is cut off the instant that the ignition is turned off.
 
jlhunsinger said:
How did you diagnose the voltage regulator? Did it start blowing fuses or was there some other indication?

I'm stumped with where to start if it isn't the voltage regulator.
Click to expand...

I dont think your problem is a voltage regulator. When mine went bad i couldnt even let the car run for more tha 5-10 seconds and it blew the fuse. Hard to say especially if someone has done a half a55 job of wiring the car. They could have ignition/charging system wired improperly or have something pulling excessive current through the 30amp fuse. Could also have an issue if they have a switch to disconnect the alt or possibly incorrect ammeter bypass wiring. Id trace your positive from the battery to the bulk head and then trace it comming out of the bulkhead under the dash and see if you can tell how they wired it theres a write up on here of the ammeter bypass ill see if i can find it
 
jlhunsinger said:
Thanks 67Dart273! I've read many of your posts the last few days and you seem to be the go to expert in this area. I've read the madelectrical article and will investigate that area soon. Do you think the load from the aftermarket electrical accessories is just overheating the fuse? What is a safe size fuse to go up to without creating too much of a fire hazard?
Click to expand...

This is a "depends" issue

"How big" is the alternator

"How much" load is on the system from lights, and say, a huge added stereo, etc

"Did these" conditions all add up in one direction at the wrong time, LOL

Additionally, there are other factors.

Let's say you parked with lights on and ran the battery down. So now the alternator is REALLY hosin out the suds

Let's say you've been idling around on a hot summer night. Hot engine bay temps DErate a fuse or breaker. This is because fuses melt to blow, and heat is what causes that, LOL
 
Happy Thanksgiving fabo,

Had a chance to work on the dart some more this morning. Verified that the fuse blows only while the car is running and alternator charging. We put as much load as we could with the alternator switch off, Radiator fans, fuel and water pump, and headlights on and the fuse was fine.

When I switched the alternator switch on we saw an increase in voltage (starter solenoid to the voltage regulator ground) for a few seconds before the fuse blew.

The car remained running as normal after the fuse blew. We had the fuse out while the car was running to verify it was blown, then when I turned the alternator switch off the car immediately died.

Any idea if I can have this professionally fixed and how to go about finding someone to do this? I'm located in South Alabama.

Pulling my hair out here.

Thanks in advance all.
 
I kept blowing fuses in my 73 dart because I kept accidentally creating a ground with a screwdriver while working in a tight area...kept wondering how the same one blew three times LOL
 
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