Car can run & start with ampmeter disconnected?

[mauibarber]

This weekend I replaced my voltage regulator because my ampmeter was pegging with just a little gas and my wires by the ammeter were starting to melt.  (69 Charger)

So I put the new one in and was fiddling with the ampmeter.  I was able to start the car with out the two wires on the ampeter connected to the ampeter or connected to each other.  I thought they had to be connected for the car to run?

Also the drivers side wire on the ampmeter gets really hot really fast.  Is it supposed to be that hot?

Thanks,
Alex

[mauibarber]

Went back out to try to tighten down any grounds, started the car again and the ampeter started smoking and the wire on the drivers side of the ammeter was super hot and bubbling the plastic housing on the connector.  Also looked like the meter was pegging again. 

After doing some research on this site I believe that my ammeter shunt has gone bad causing the darn thing to take on all the voltage.  The only wire thats hot to the touch  is the one coming off the main alternator wire under the dash going to the ammeter. 

Plus the ammeter is literally cooking after only a minute being on.  There is smoke inside of it!  I'm going to order a new Ammeter and replace.

Does this sound like a good diagnosis?

[Needa68]

Alex: I don't profess to be an electronic expert but after looking at the wiring diagrams it appears that as long as you have enough battery to start the engine that it should run with the ammeter out of the circuit.

Concerning the hot wire.... suggest you take a look at this thread:

http://www.dodgecharger.com/forum/index.php/topic,45439.0.html

Another great tread to review concerning hot wires is this one:

http://www.dodgecharger.com/forum/index.php/topic,33574.0.html

[mauibarber]

Would the "Nacho fix" solve the problem enough where the kit you purchased wouldn't be neccessary?  I'm not sure I need that kit because I have no AC or heater, rarely drive the car at night, have an upgraded alternator, and just a basic  4 speaker stereo.  So I don't put much load on my car except for some electric fans but the bigger alternator seems to compensate fine for the fans.

Also heres a $10,000 question.  If my ammeter shunt went bad could that cause any problems with the big black and red wires (alternator and battery) at the bulkhead or would these not be effected?

Since the ammeter shunt doesnt effect the charging of the car I am thinking it wouldn't have much to do with the charging system?
Perhaps my big red and black wires got burnt at another time?

[Needa68]

Question: Would the "Nacho fix" solve the problem enough where the kit you purchased wouldn't be neccessary?

Comment: I believe it would!

Question: If my ammeter shunt went bad could that cause any problems with the big black and red wires (alternator and battery) at the bulkhead or would these not be effected?

Comment: I guess if it shorted to ground it could be the cause. More than likely a short occured elsewhere. The real question is did the wires burn this time or at some other time.

Statement: Since the ammeter shunt doesnt effect the charging of the car I am thinking it wouldn't have much to do with the charging system?

Comment: If I'm tracing the circuit properly it appears the ammeter is part of the battery charge path. If it's bad I don't believe your battery will charge. I can't find the shunt you reference in the schematic therefore I assume it is parts of the ammeter. I just physically examined the instrument panel out of my son's 68 Charger. I didn't remove the ammeter nor did I see what looked like a shunt.

[mauibarber]

Correct, the shunt is inside the ammeter.  It regulates the flow of electricity into the ammeter.  If the shunt fails it takes on the full amount of electrcity where normally it only takes a small percentage of the total juice coming through the alternator wire.  This will give you false readings of course because it says its charging +60 amps.   

The meter cant take this amount of juice and literally burns up. I hope this is my problem.  I replaced the voltage regulator and checked all the grounds.  The car runs properly and the only wire getting hot is the one off the ammeter.  And the Ammeter is smoking as well.

I think in the coming weeks I will do the "nacho fix"

For more about how important the shunt is go to..
http://www.allaboutcircuits.com/vol_1/chpt_8/4.html

-Alex

[Just 6T9 CHGR]

I have bypassed the ammeter on mine by just connecting both wires on one leg of the ammeter  AFAIK the ammeter completes the circuit for the starting/charging system.  Or you just connect both wires together to complete the circuit.

[Shakey]

I have bypassed the ammeter on mine by just connecting both wires on one leg of the ammeter  AFAIK the ammeter completes the circuit for the starting/charging system.  Or you just connect both wires together to complete the circuit.

That's what I did when I wanted to start my car and the cluster was not installed.

[375instroke]

The shunt is what Mopar did in the '70s to increase the capacity of the amp gauges they used, but it reduced their effectiveness since some current was going through the shunt.  I have an ammeter that went out and I just connected both wires to one terminal.  Why did yours fry?  The fusible link should have gone first.

[mauibarber]

Why would the fusible link go first if normal current was going through the link. 

From my understanding when the shunt goes, then all the current goes through the ammeter.  This fries the meter and/or gives off a incorrect reading.  If the shunt goes its not that the car is getting to much or to little juice, its just the meter is gettin fried.

Please explain why the fusible link would blow up first?

I've ordered a new ammeter.  If this doesnt correct the problem then I don't know whats left?  I've replaced the voltage regulator and nothing changed.  I have also inspected the grounds of the alternator and they were fine.  The only wire getting hot is the one coming off the alternator wire and into the ammeter.  And of course the ammeter itself is smoking.  In fact when I honk the horn, puffs of smoke come out of the ammeter.     But the other wires are all cool to the touch.