Suddenly no juice

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1973_Scamp

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Finally, i go my 1973 Scamp 318 all stock running with minor change such as:
2176 edelbrock intake
1406 carburetor
Procomp HEI distributor with PC-91 Coil
Mini starter

Engine started at every turn
Then i decide to connect the tachometer. After installation, i cranked the ignition switch, then i hear something inside engine compartment. Then nothing work. It fail to turn. I lost all power to the car including headlight, horn, doom light, signal.etc everything is dead
Things i checked:
Battery at 12.6V
All fuses under steering column seem OK

Help,,,,,
scamp
 
So what exactly did you hear inside the engine compartment before everything stopped working? It does sounds like the fusible link....disconnect the tachometer completely before you replace it and try again.
 
I hear some hissing noise then nothing working, remove the Tach and still no juice. I checked fusible link cable and it turn out to be the red cable at the center of bulkhead connector of the fire wall. I checked at local 95148 Napa, autozone, and Oreilly and the don't have it. Is there a way to by pass fusible link by using a fuse in between? If so how much amps should I be using?
Thanks
Scamp
 
Here's what you are up against

The original charging wire is only no 10 which in house wiring, is only rated for 30A service. But "in the day" you were likely to encounter a 60A alternator!!!

I don't think anyone ever "knew" what the original fuse links were rated for in amps, they had a mopar part number, but they had to handle the alternator amperage. So if you are going to sub say, a big stereo type fuse in there, you need something that will handle your alternator, so probably at least a 40A fuse, and "guesstimate" derated enough to compensate for engine temperature. Are you starting to fell like there are complications?

NAPA used to, back when they were a "real" parts store, used to sell "universal" fuse link wire. I haven't asked them about this in years.
 
Part stores do have fusible links in their electrical supplies. It wont have the same factory service disconnect on it.
A inline fuse holder would need to be of sufficient grade in its wire and terminals, like a maxi fuse holder maybe.
 
Yep, the 40A Slo-Blow (not fast blow) maxi fuse sounds like a good place to start; it will not blow a few 10's of seconds with amperage in the 50-60 amp range. so should withstand some excess current. But I would find a fusible link for the long term, as it avoids the issues of a fuse and fuse holder in long term, high current uses. Look here: http://www.madelectrical.com/catalog/fusible-link.shtml

And Dorman still sells fusible link wire; it is on the Jegs site. (Gosh, I can surf the web fast! lol)
 
Ok
I used 12 gauge (rated for 30 amps) ATO fuse holder (FHAC2BP) from O'Reilly with 40 amps. After everything was in place, I hooked up battery, turned on head light, and started engine and it started without hesitance. Everything is back to normal for now. Next step is to replace 40amps fuse with 30amps, then 25amps and so on.........i just want to ensure when it going to fail .........
Thanks guys
 
Uh..................the fuse has to be as large as the output of your alternator..................at least
 
67Dart273 said:
Uh..................the fuse has to be as large as the output of your alternator..................at least
Click to expand...

If that was the case... the main breaker in my home panel would match the amperage my power company can supply.
Some of the modern alternators can throw 120 amps. Anyone ever spotted a 120 amp auto fuse ?
 
The fuse rating has to be large enough to last through a surge of up to the max amerage rating of the alternator and not blow. With a slow blow, the fuse can take amperage well OVER the fuse's rating and not blow for some period of time. Here is the link to the Maxi-fuse dataq sheet:

[ame]http://www.littelfuse.com/~/media/automotive/datasheets/fuses/passenger-car-and-commercial-vehicle/blade-fuses/littelfuse_maxi_32v_datasheet.pdf[/ame]

It shows that at 135% of rated amperage, it takes from 1 minute to 30 minutes to open. So with a heavily discharged battery, how long will the alternator try to shove 60A to the battery??? It would have to be longer than a 40A fuse's blow time rating at 150% of rated current.

A fusible link is not anywhere rated at 60A; it depends on the same thing to open: heating that will blow it but if the overload % is low, it will take a long time.

To the OP, I would advise replacing the fuse with a fusible link not too long from now. The weak link in your temporary setup the holder; it will tarnish and then heat up and then lose contact and springiness to grip the fuse blades. And your experiment is interesting, but only valid if you try it with the fuse loaded to maximum, which requires that you have a heavily discharged battery each time you try it. Next heavist load through the link is likely with the car not running and headlights, heater blower motor, etc, turned on.

Glad you found the issue !
 
RedFish said:
If that was the case... the main breaker in my home panel would match the amperage my power company can supply.
Some of the modern alternators can throw 120 amps. Anyone ever spotted a 120 amp auto fuse ?
Click to expand...

I don't know what YOU are thinking but that IS the case. All the alternator supplies goes through that link.

And remember, most these old girls only had about a 45a alternator

Furthermore, All the house can draw goes through the main breaker to your house!!!!
 
67Dart273 said:
I don't know what YOU are thinking but that IS the case. All the alternator supplies goes through that link.

And remember, most these old girls only had about a 45a alternator

Furthermore, All the house can draw goes through the main breaker to your house!!!!
Click to expand...

And that main breaker is 200 amp. It protects everything beyond it. It doesn't know or care what the maximum supply could be.
The fusible link is supposed to do the same , protect everything beyond it.
I don't care if the alternator can put out 200 amps. I don't want that going into the cabin of my vehicle.
If I'm wrong, I'm a happy idiot.
 
Red I don't understand your logic, here. If you leave your headlights on, and jump your car, that 80A alternator you've installed is going to output 80A back to the battery. And if you've installed a 30A fuse link, I can flat guarantee you that the fuse link is going to blow up.

As I tried to explain to you earlier, most these cars only came with about 45A alternators

(The above are examples, use whatever numbers you want)

Ma knew this wiring was marginal, which is why "she" provided "fleet taxi" wiring for 60-65 A optional alternators, and which is exactly why I preach NOT putting heavier more modern alternators on these cars without changing the wiring.

I can also guarantee you that if you put enough load on the main breaker of your house panel, you'll pop that thing, too!!! You might not even have to do anything remarkable. I might be able to do so by simply turning every darn thing on in the house, pluggin everything in that I can find, then going out and tripping the breaker, and flipping it back on. It will trip from the inrush load!!!!
 
I wont argue with any of that. The fusible link ( like any fuse ) is a devise meant for protection.
If it blows for any reason... I'll be happy to replace it.
 
67Dart273 said:
I don't know what YOU are thinking but that IS the case. All the alternator supplies goes through that link.
Click to expand...
Don't you mean all of the battery charging current supplied from the alternator goes through this link? (Which indeed could be somewhat near to the max alternator amperage with the alternator cold and battery near dead.) Per the schematics, a lot of (most of) the loads don't flow via this link when running off of the alternator.
 
That's right the entire load does not go through the link but the entire BATTERY CHARGE load goes through the link, so as I said, in the particular case when the battery is low, and the thing is charging for "full tilt" the link sees that full amount of current

This goes back to my original premise......I don't believe I've actually ever seen an amperage rating for the OEM links in these cars.

The other thing about "protecting" this wire

You compare this charging wire to house wiring, there is basically two issues--temperature and voltage drop

The way these cars were originally wired, voltage drop is not a huge issue, because if the charging load is high, the regulator just keeps compensating. Heck there could be 3V drop between the alternator post and the battery and it would not be the end of the world

Likewise, temp. The BIG thing that fails is and has always been the blessed connector terminals in the bulkhead. I've said this before...........I used to service heat pumps and electric furnaces, and these things use the same 1/4" quick connect terminals, and they fail all the time. These carry nominal 20A or so per element in a furnace so why would we expect them to carry more against a hot hot hot engine with a 45A --65A alternator?

As long as the wire temp doesn't get so high that the insulation falls off, LOL, that's not a real big deal. The other thing is duty cycle. Ma, Ferd, and "General" Motors all three figured they could "get by" They all figured that "mos'ta time" we'd jump in, star 'ter up and drive off, the battery'd charge right back up and every thing 'ed be real gud. And it 'twas.

(Many 220-240V elements are 5KW each which is about 20 amps draw)

Typical elements, limits, and controls in an electric furnace. I used to replace LOTS of these, all use the same 1/4" quick connectors

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