Fusible link melted!

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73 gld dstr

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Hey y'all
The other day I went to start my car and saw smoke coming out of the hood so I immideatly unhooked my ground and found out that my fusible link by the bulkhead connector had melted. All I know it the wire comes off the starter relay, goes through the fusible link and bulkhead connector, goes to the ammeter, then goes back through the bulkhead connector and to the alternator. Should I buy a connector and replace it or have someone look at it? My brother says they are notorious for going bad (especially being 40 years old) haha
Thanks!
Corey
P.S it's a 73 Duster with a 318
 
Hey Corey dad and I had the same problem and it turned out to be a bad alternator. Del(67dart273) diagnosed the problem. Give him a bit and I am sure he will chime in.
 
First thing to do is get a lamp in series with the ground lead of the battery. This will show if the system is drawing current.

Then make SURE EVERYTHING is shut off, check the trunk light, dome light, glove box, ANYTHING, and yank out the cigarette lighter.

Next pull out ALL the fuses

Then jumper around the fuse link. Smart way to do this, until you find the problem, is buy an inline fuse holder and get some 20A fuses

(You'll have to jumper the fuse link to do any testing)

With everything above unhooked, and the light still comes on as Steve says, unhook the main alternator wire.

From there it's a matter of unhooking stuff until you find the problem

Look at the simplified MAD diagram, which represents the "main feed" from the battery, through the bulkhead, and back to the alternator

Look at the diagram below. The battery main feed is represented by the red wire, through the fuse link, through the ammeter, and back out the bulkhead to the alternator

NOTICE the "welded splice". This is a factory splice under the dash, taped up in the harness. You can examine it by untaping from the ammeter, following the black ammeter wire until you get to the splice

This splice supplies UNFUSED power to

the ignition switch

the fuse panel "hot" buss"

the main headlight power (breaker in / on the switch)

the wiper switch on at least some models (breaker on/ in the wiper switch)

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

Also SUSPECT that other wires IN the harness have melted/ welded together. It would be a WISE idea to unwrap the underhood harness if there's evidence that this "came from" the alternator, and certainly do the same with the under -- dash harness

IF you have made changes to the wiring, suspect those. As I said, the ignition feed is NOT fused, is ONLY protected by the fuse link, which will NOT protect the smaller size ignition wires. So if you've added a tach, or changed the ignition system, check that out carefully

amp-ga18.jpg
 
73 gld dstr said:
Hey y'all
The other day I went to start my car and saw smoke coming out of the hood so I immideatly unhooked my ground and found out that my fusible link by the bulkhead connector had melted. All I know it the wire comes off the starter relay, goes through the fusible link and bulkhead connector, goes to the ammeter, then goes back through the bulkhead connector and to the alternator. Should I buy a connector and replace it or have someone look at it? My brother says they are notorious for going bad (especially being 40 years old) haha
Thanks!
Corey
P.S it's a 73 Duster with a 318
Click to expand...


now DO YOU SEE 67's post ? you need to BYPASS the ammeter and rewire it as shown above. TRUST ME IT WORKS
this is how i did mine , and i added a VOLT gauge
o riellys has the new fusible links for FIVE bucks
 

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Just bypass the bulkhead connector and be done with it.
 
You guys are embarassin' me. I've made my share of mistakes, and still do

Here's one I made years ago:

Late one night, "no heat" call at a !!!CHURCH!!! So I roar down there and determine that the combination fan/ limit switch is bad, go out to the truck, throw one in, and stand there and watch as...................

the control transformer, the gas valve, and the thermostat all go up in smoke

WHY?

Because Honeywell "universal" fan/ limits come with the fan and limit switches jumpered together at the common point of the switches

Some furnaces have the limit in the 24V control circuit, and some are in the 120V transformer supply. I neglected to check this, did not cut the jumper, and so I got to replace ALL those parts...............fer free

2012-02-17_003614_fanlimitgraphic.jpg


Fan_Limit_Switch576-DFs.jpg
 
had the same thing happen to my 67 cuda, it ended up being the distributor causing it.
 
If you want a cheap, simple voltmeter, you can get a small LCD that plugs in the cigarette lighter for ~$15 on Amazon or ebay. I use an Eqquis one in my newer cars that don't have a charging indicator. One would look nice in my 64 since it has the lighter on the dash.
 
BillGrissom said:
If you want a cheap, simple voltmeter, you can get a small LCD that plugs in the cigarette lighter for ~$15 on Amazon or ebay. I use an Eqquis one in my newer cars that don't have a charging indicator. One would look nice in my 64 since it has the lighter on the dash.
Click to expand...

I find cheap tools are just that - CHEAP - and they usually fail when you need them the most.
 
Hey guys. After hours of troubleshooting I figured out that my short was in my ignition switch. I replaced it and the car started and ran awhile but the same fuse blew again(I replaced the fusible link with a 12 ga fuse holder). I had a 20 amp fuse in it then I put a 25 amp fuse in it and so far it had done fine. Is the 25 amp fuse big enough? I thought that the fuse probably had a lot of current going through it because the battery was deader than a door nail
 
NO, you cannot use a fuse that small

ALL of the charging current from the alternator goes through that fuse, if you look at the simplified diagram posted above. The fuse link is meant to be a "last ditch" device for that reason, as opposed to regular fuses.

I find it difficult to believe that your ignition switch was the original problem
 
You need at LEAST as large as the alternator can put out, IE 40--60A, or more than your alternator is rated for. That is why Ma used a link and not a replaceable fuse.
 
I agree that it probably wasn't your ignition switch since that just switches components on the high side (12 V). It would have to be really messed up to short a wire to ground, which is your likely problem from a frayed wire. Post a photo of your under-dash wiring. You won't scare us, we have seen some amazing junk, including all the old cars I have bought that went thru monkey owner's hands.

The problem could also be that the fusible link was just old and corroded, in which case replacing it would work. If you put in an upgraded alternator like the square-back type, that is a sure way to blow the link or worse. I agree that you should bypass your ammeter, in the engine bay. Many posts on that.
 
Well i used my ohm meter to find the short and under my steering colum there was is a connector that goes to the ignition switch. When the connector was plugged it I got .2 ohms (almost a dead short) but I found that when I unplugged that connector I didn't read a short anywhere. So I replaced it and it ran for awhile until the small 20 amp fuse blew. I guess I'll run get a 30 or 40 amp fuse tomorrow. Oh and when I was troubleshooting I did bypass the ammeter.
 
73AbodEE said:
now DO YOU SEE 67's post ? you need to BYPASS the ammeter and rewire it as shown above. TRUST ME IT WORKS.....
Click to expand...
YES! YES it does! Beautifully.
I did this ByPass a couple of Years back & I can Confirm the effectiveness of this 'surgery'. I coupled that w/ the newer Voltage Reg, a 65amp Alternator & tracing/ replacing a lot of old connectors & some wiring. This car now starts, charges & sparks great.

Actually, I do need to do some more 'surgery' at the Bulkhead Connectors. THey really, really suck. I have run into some starting at speed & blown fuses for the Brake Light/ Rear Lights. That fix should be relatively simple, but will require some trackin' down the gremlins.

If anyone has some suggestions for Refurb'ing Bulkhead Connectors, I'd love to hear about 'em.
 
73 gld dstr said:
Well i used my ohm meter to find the short and under my steering colum there was is a connector that goes to the ignition switch. When the connector was plugged it I got .2 ohms (almost a dead short) but I found that when I unplugged that connector I didn't read a short anywhere. So I replaced it and it ran for awhile until the small 20 amp fuse blew. I guess I'll run get a 30 or 40 amp fuse tomorrow. Oh and when I was troubleshooting I did bypass the ammeter.
Click to expand...

You got .2 ohms from where to where? With the battery hooked up or what?

If you had a short TO GROUND of .2 ohms, it should have turned the fuse link into vapor and probably would have fizzled half the harness into a smouldering mass of semi melted, multi-colored plastic
 
Did all of the smoke come out???

Electrical components run on smoke. Smoke to them is like blood to us. Once too much of it escapes, that component dies and cannot be revived. Therefore if you allow too much smoke to come out of your electronics, they won't work anymore...
 
Question, do you have to bypass the ammeter in the above drawing? Could you do everything but bypass it? Seems like if you are not adding anything to the underdash load just leaving in place would be fine. You still get both wires sharing the underdash load and any extra big loads could just be added to the starter relay or battery post. If you don't bypass it what would it read? nothing? I just re-did my dash and don't want to pull it our again, I have my whole forward harness out and am re-doing what looks bad there.
 
If you are saying bypass the meter under the hood, but leave the ammeter untouched, that is MAYBE OK if the ammeter circuit is OK. But if the ammeter happens to be part of the problem, then no.

Actually, some of the cars used a sort of a "partial" bypass which acted as an external shunt for the ammeter. I would guess the bypass might be, say, a no 12 wire, so part of the current went through the bypass, and part through the ammeter
 
My car has no current problems, I'm just cleaning up the engine bay and figured I'd do underhood part of this now. The shunt bypass seems like a good idea too, just run a whole new 10 gauge wire around the ammeter?
 
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