old topic, new question. charging

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player1up

player1up

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My 73 /6 duster is showing discharge at the ammeter at idle (650RPM) but voltage is correct above idle (13.8 to 14.7 with volt meter at the battery)
I haven't bypassed the ammeter yet (i'm using it as a tach :) )

I've been looking through the forums and some say it's just the way old mopars are, others say get a smaller pulley for the alt, even others say up the idle a little..

so where do I get a smaller pulley for the alt?
or buy a new higher amp alt?

I'm asking because I only live about 5 miles from work and most of it is sitting in traffic with the car at idle...

Thanks
 
might be easier to get a bigger crank pulley. or up the idle a little.
 
player1up said:
My 73 /6 duster is showing discharge at the ammeter at idle (650RPM) but voltage is correct above idle (13.8 to 14.7 with volt meter at the battery)
I haven't bypassed the ammeter yet (i'm using it as a tach :) )

I've been looking through the forums and some say it's just the way old mopars are, others say get a smaller pulley for the alt, even others say up the idle a little..

so where do I get a smaller pulley for the alt?
or buy a new higher amp alt?

I'm asking because I only live about 5 miles from work and most of it is sitting in traffic with the car at idle...

Thanks
Click to expand...

OK, I'll bite! How do ya use the ammeter for a tach???

I like the ammeter, others think it's Devil spawn and the root of all electrical evils. I've never seen one fail as you describe - I've seen ONE that burned out and a whole bunch that work just fine. So to narrow the search a bit:
Did it just start behaving that way, or was there a major electrical event just before. Does the ammeter come to the middle of the gauge when the engine is off. Does it go further to the discharge side with higher revs (that would be due to having the wires on the alternator reversed) With those answers, I think the problem and the cure will become clear.

And how DO ya use an ammeter for a tach, anyhow???

BC
 
ragtop, I'm trying to get the car "ready" for the wife to drive (if she needs to) and right now there are too many quirks. I just don't like to leave it idling at -15amps for too long. As for using the ammeter as a tach.. while idling it is at -15/-20 and when I rev it up the meter swings to the +15 side till it charges back up... so it behaves like a tach. :lol:

but I think my problems are worse than that, this morning the ammeter pegged at -40 for an instant ( really fast ) and then came back up. I've got something bad about to happen and I hope I can figure it out before the thing catches fire or strands me somewhere. and yes I keep 2 spare ballast resistors and a spare voltage regulator in the glove box, not to mention enough tools in the trunk to pull the motor on the side of the highway.

I was going to bypass the ammeter but if I do it now I wont be able to see if it flicks to discharge. :(
 
Only one slant six car I've owned had a weak charging system. Her headlights would dim at idle then blare up upon acceration. At idle the turn signal draw would twitch the amp gauge needle. Amp gauge was the culprit. The armeture in the gauge is magnetic. I cleaned all the tiny rust particles out of it, cleaned and tightened the wire connections and it improved but still not a total fix until I cleaned corrosion at bulkhead terminals (fusible link). All this was over 20 yrs ago. Wish I had internet help back then. LOL
 
I had an issue years ago that sounds the same in an Australian 1965 valiant.
Now it would have had a bosch alternator but I imagine all alternators are built the same?
An auto lecky checked it and apparently there is a part inside called a diode plate which has 5 diodes.When 1 0f the 5 diodes is blown the symptoms are as you describe.
For differerent reasons I've had some chargin problems recently in my 69 barracuda.Here's a thread on an Aussie forum with some very knowledgeable replies.May be of some help.


http://www.moparmarketforum.com/phpBB/viewtopic.php?t=12902
 
player1up said:
.....I just don't like to leave it idling at -15amps for too long. As for using the ammeter as a tach.. while idling it is at -15/-20 and when I rev it up the meter swings to the +15 side till it charges back up... so it behaves like a tach. :lol:

but I think my problems are worse than that, this morning the ammeter pegged at -40 for an instant ( really fast ) and then came back up. I've got something bad about to happen and I hope I can figure it out before the thing catches fire or strands me somewhere. and yes I keep 2 spare ballast resistors and a spare voltage regulator in the glove box, not to mention enough tools in the trunk to pull the motor on the side of the highway.

I was going to bypass the ammeter but if I do it now I wont be able to see if it flicks to discharge. :(
Click to expand...

I would bet the change in my pocket that you have problems with the diodes in your alternator. OK, I'm a cheapskate - I can (and do) live with it! At first I was thinking you had somehow actually put the ammeter into service as an actual tach. Now THAT would be a trick I would need to know more about!

After reading your second paragraph, The alternator diodes seem most likely. The easiest fix is a new or rebuilt alternator. I'm pretty sure it wouldn't catch fire - stranded is much more likely. But again, I think a properly functioning alternator will straighten it out. You're certainly better equipped than most (and better equipped than me) for the more common problems with the spare ballasts and regulator. I'll get those when I get to a point where I'll be on the road for a while. Thanks for the reminder.

BC
 
thanks all, I'll be checking it out tonight. I don't normally post electrical stuff since most of it is fixed by pouring yourself into a ball of wires until you find the problem. All of my dusters (3) have had the slight discharge at idle and bouncing ammeter needle with blinkers on, but not like this. oh and the negative spike on the ammeter just started happening today and it is not like the bounce with the turn signals, it's almost lighting fast. oh well I'm on the hunt! like trying to find the hay in a needle stack.. :lol:
 
ok so if the ground strap from the motor to the firewall is disconnected, would that cause problems?!?! DOH.. I feel like such a pole

Seriously, I checked the grounds at the engine, firewall, voltage regulatorn and ignition box, and I have never seen the ammeter so stable. I guess it goes to show, NEVER take anything for granted..
 
Glad you found it before investing a lot of money. That has to be the most overlooked item for most any electrical problem. I have seem many "professional" mechanics stumped by electrial problems for not reconnecting the ground straps (that and rusty ground connections).
 
player1up said:
ok so if the ground strap from the motor to the firewall is disconnected, would that cause problems?!?! DOH.. I feel like such a pole

Seriously, I checked the grounds at the engine, firewall, voltage regulatorn and ignition box, and I have never seen the ammeter so stable. I guess it goes to show, NEVER take anything for granted..
Click to expand...


I just bought my 69 dart and having the same problem. The guy that had it before me never grounded the engine to frame i can see the ground wire hanging from the frame. Good to know that when I get back in town I just have to hook that up and will possibly have no more problems. Hopefully

the alternator and battery look brand new so we will see.
 
Ya just can't HAVE too good a ground system in a vehicle! The years and miles and God ONLY knows how many repairs, skilled and unskilled have contributed to grounding issues. Electrical problems - look for grounding faults! If in doubt, GROUND IT!
 
Ragtop, That is good advise, back when the car was new I imagine it worked like a charm, but add 30 some odd years to every spot weld and mating surface then add PO "fixes" and who knows what kind of issues you will have. It's a good thing my motor mounts were shot or I wouldn't have ANY ground :lol:
 
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