Factory ammeter

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I ran the voltage test, I found about 1.5 volt drop at the bulk head connector. After that connection the rest of the system didn’t drop much. I have about the same voltage on the inside of the bulkhead connector and at the battery when the car is running.
I ran the test with an old alternator and everything seem to settle down, the amp gauge was about 1/2 way between the middle and full charge. Then I put the original alternator back in and things went haywire again. Amp gauge was way up and the alternator belt was squealing a little, like it was really working. Output voltage went up to around 17. So I was starting to put the other alt. Back in and the connector pulled off the positive field wire and i stopped there. I’m going to solder on some new terminals.
Could this alternator that’s acting up be a 65 amp? I did notice in my wiring diagrams it shows different wiring for the 65 amp alt. This car also has a single pole ballast resistor, shouldn’t it have a dual being a ‘75?
 
The voltage drop is proportional to the resistance AND the current flowing through that resistance.
Is this 1.5 Volt drop in the alternator output wire connection?
So putting these together, if the ammeter is showing 1/2 way up the charge level, that's about 20 amps to the battery.
The alternator field and the ignition are taking abother 5 amps. So that's about 25 amps through the alternator output wire.

Its not clear to me whether the newer one is acting up, or is cabable of providing much power at idle speeds than the old one.
All alternators produce much more power above idle speed. Lets say when regulated to 14 v the old one maxes out at 25 amps at 650 rpm, and the new one can produce as much has 45 amps at 650 rpm. And lets say the battery is low and when given power at 14 V will try to draw 50 amps. That creates lots of problems most of which are obvious - such as 40 amps is more than the circuits are made to handle - charging a battery that fast will cause it to get hot and charge poorly - maxing out the alternator is hard on its wiring. Another is that the voltage drop at the connector will be nearly twice what it was with 25 amps flowing through it. Voltage drop = current x resistance.

I would start by cleaning the terminals. Tighten them up as needed and make sure they are secure when you reinstall. Look at the wire condition at the crimps as well.
You can find some posts about disconnecting the bulkhead connector, as well as removing the male and female terminals.
New seals are available from DMT.

If the terminals are compromised there are a few different ways to improve the flow path.
Some people drill straight through the connectors and join the wires. I don't like that because it makes it difficult to service and diagnose any of the other circuits in that connector.
My suggestion is to take a cue from one of the methods mopar used when installing high output alternators. The most common one people have posted photos of here seems to be on cars equiped with rear window defroster grids.

What I did on my '67 was a parallel wire feed to terminal stud. This is similar to what Chrysler did for some 60 and 65 amp alternator equiped cars with options other than the rear window defrost.

upload_2020-10-14_23-5-53.png

I chose to use the terminal mounted in the factory location because I wanted to power the MSD, and didn't want it pulling power through the ammeter.
In this car the alternator output terminal in the bulkhead was OK, but had some overheating damage. Damage I can almost certainly pin on a low battery recharging situation.
So the way its wired now there are two paths from the alternator to the main splice. Current will take the path of least resistance, normally the shortest but this way there is some redundency.
upload_2020-10-14_23-20-7.png


If you have no need for a terminal stud, you can run the parallel wire direct through a grommet to the ammeter's stud. This assumes your ammeter is relatively accessible and that it is an internally shunted ammeter.

Anyway the point is there's a number of ways to skin the cat besides drilling through the existing connector.
 
gm1236 said:
This car also has a single pole ballast resistor, shouldn’t it have a dual being a ‘75?
Click to expand...
I beleive you are correct. However the second resistor, which was 5 ohms, was to regulate power to the ECU. Later ECUs, and most (possibly all?) replacments today handle this internally.
But it does suggest someone has done some rewiring.
gm1236 said:
Could this alternator that’s acting up be a 65 amp?
Click to expand...
Some of the 60 and 65 amp alternators had different voltage regulation wiring than standard Chrysler alternators.
All cars equiped from the factory with 60 or 65 amp alternators had a heavier output wire and a grommet through the firewall as part of the arrangement.
 
To illustrate the current relation to voltage drop.
upload_2020-10-14_23-51-41.png


V=I x R
1.5 Volts = 25 amps x Resistance
.06 Ohms = Resistance.

Lets now say the current is 45 amps.
The votlage drop will increase proportionally.
V = 45 amps x .06 Ohms
V = 2.7 Volts
Now what's the regulator going to see and how will it react?

Once the battery is charged (or replaced if defective), the typical current flow will be 5 amps or less.
Now what happens to the voltage drop?
V = 5 amps x .06 ohms
V = .3 Volts
Everything works like normal...
until the lights and other stuff is turned on...
 
Mattax said:
The voltage drop is proportional to the resistance AND the current flowing through that resistance.
Is this 1.5 Volt drop in the alternator output wire connection?
So putting these together, if the ammeter is showing 1/2 way up the charge level, that's about 20 amps to the battery.
The alternator field and the ignition are taking abother 5 amps. So that's about 25 amps through the alternator output wire.

Its not clear to me whether the newer one is acting up, or is cabable of providing much power at idle speeds than the old one.
All alternators produce much more power above idle speed. Lets say when regulated to 14 v the old one maxes out at 25 amps at 650 rpm, and the new one can produce as much has 45 amps at 650 rpm. And lets say the battery is low and when given power at 14 V will try to draw 50 amps. That creates lots of problems most of which are obvious - such as 40 amps is more than the circuits are made to handle - charging a battery that fast will cause it to get hot and charge poorly - maxing out the alternator is hard on its wiring. Another is that the voltage drop at the connector will be nearly twice what it was with 25 amps flowing through it. Voltage drop = current x resistance.

I would start by cleaning the terminals. Tighten them up as needed and make sure they are secure when you reinstall. Look at the wire condition at the crimps as well.
You can find some posts about disconnecting the bulkhead connector, as well as removing the male and female terminals.
New seals are available from DMT.

If the terminals are compromised there are a few different ways to improve the flow path.
Some people drill straight through the connectors and join the wires. I don't like that because it makes it difficult to service and diagnose any of the other circuits in that connector.
My suggestion is to take a cue from one of the methods mopar used when installing high output alternators. The most common one people have posted photos of here seems to be on cars equiped with rear window defroster grids.

What I did on my '67 was a parallel wire feed to terminal stud. This is similar to what Chrysler did for some 60 and 65 amp alternator equiped cars with options other than the rear window defrost.

View attachment 1715613045
I chose to use the terminal mounted in the factory location because I wanted to power the MSD, and didn't want it pulling power through the ammeter.
In this car the alternator output terminal in the bulkhead was OK, but had some overheating damage. Damage I can almost certainly pin on a low battery recharging situation.
So the way its wired now there are two paths from the alternator to the main splice. Current will take the path of least resistance, normally the shortest but this way there is some redundency.
View attachment 1715613052

If you have no need for a terminal stud, you can run the parallel wire direct through a grommet to the ammeter's stud. This assumes your ammeter is relatively accessible and that it is an internally shunted ammeter.

Anyway the point is there's a number of ways to skin the cat besides drilling through the existing connector.
Click to expand...
Thanks Mattax,
The bulkhead connection on my car looks like it has been hot, I planned on bypassing it, but your suggestion of a second wire may be an easier option. In the photo, the red wire powers the MSD, the black wire from the harness is from the alt. Stud, where does the other black wire going through the firewall connect?
Thanks again for the reply, very informative.
 
gm1236 said:
where does the other black wire going through the firewall connect?
Click to expand...
It goes to the ammeter's black terminal. I had the instrument panel out anyway for speedometer repair so this was a good time to do it. The ammeter connections in the rally panel are difficult to access with the panel installed so I had been waiting for the opportunity.
upload_2020-10-15_22-59-48.png

I used a small grommet in the firewall but was considering a factory style one if I could have found one. They look like a big bottle stopper. If I had also run the battery wire through the firewall I would have kept looking for a bigger grommet.

Your '75 firewall may be a little different, but the indentations for various unused optional pass throughs will be there.
Here I'm starting to mockup the length of the wire from the alternator.
upload_2020-10-15_22-46-5.png


upload_2020-10-15_22-49-11.png
 
Thanks Mattax, I’m going to pull the gauge panel and see how it looks. Is the black amp gauge wire where I want to connect the wire from the alt? I’m thinking of running a second wire, rather than bypassing the connector.
 
Yes. Chrysler seemed consistant with that. Red for battery connection and black for alternator output.
The back of the ammeter may even have R next to the stud for the red wire. At least on mine, there was no mark on the side connecting to the alternator/main splice.

In '67 the wires were 12 ga. '75 might be 10 ga ?? Cars with the rear window defroster grids got 8 ga!
I'd suggest 12 AWG Marine wire at a minimum, and 10 ga would be better. Marine wire is made with smaller strands and is slightly denser for the same gage diameter tha automotive gages. I find its also easier to work with. Due to the restrictions on in-person retail I ended up ordering 10 ga GXLautomotive from Wirebarn for the main run to the stud.

The ammeter studs were #10 and the alternator output stud 1/4" diameter. Look for ring terminals with decent contact surface but not so big as to risk easy shorting.
I saw a lot for sale on-line that had insulation that looked like it would get in the way of the connection. :(
The ring terminals I bought were 'F-crimp' - IIRC made by AMP - TE Connectivity
upload_2020-10-17_7-29-30.png

They were actually a bit of a pain to work with. I had to trim the wings a little to fit the wire tightly and due to the thickness they didn't crimp easily.
upload_2020-10-17_7-33-29.png


Then heat shrink tubing to cover the crimp area.
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For something to compare the condition of yours to. This was the condition of the bulkhead terminal from the alternator when I checked on it in. The rubber seal had melted and there is slight discoloration of the metals but overall not terrible. This is part of a 25 yr old replacement harness. I'm pretty sure the damage was done 2016 when I was forced to recharge a very low battery off the alternator.
upload_2020-7-1_17-37-20-png.png
 
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I ran a 10 ga. Wire from the alternator to the post with the black wire on the ammeter. The ring terminal on the red wire had been replaced and looked corroded, so I replaced that also. I solder and heat shrink all the connections.
I ran the new wire, put everything back together and drove the car. The amp gauge stayed between the middle line and full charge line and seem to be charging more the longer I ran it. So I took the battery out and charged it, it was very low, took a few hours to get back to normal. I did put another know good battery in and the amp gauge stayed between the center and + middle charge line, but I was getting 15 volts at the battery. The voltage drop from the alternator to battery is less than 1 volt now. I’m going to put the charged battery back in and see what it does.
 
With the 2nd alternator and s fully charged battery everything seems ok. The ammeter is running just right of center. I have less than 1 volt drop from alt. To battery.
Thanks again Maddax and 67dart273.
 
Seems like you got it, or at least the worst of it.
If you still find difference between the alt out and the VR, column connector is another place to look.
That carries a fairly high load when the choke assist is on, and when accessories are on (wipers, turn signals, etc).
 
67Dart273 said:
Actually in some cases it is BOTH the ammeter and bulkhead connector. The whole circuit is simply not heavy enough for heavy current applications. I melted the ammeter mounting bosses somewhat in my 70RR cluster way back in the mid 70's before Al Gore invented the internet. AND the same car suffered damage to the bulkhead connector terminals.

Even in 70?-72, some of the large sea barges used external shut ammeters which eliminated the problem. "Ma" knew the problem was there, as the cars with optional 65A alternators used modified harnesses to combat the problem. This is known loosely as "fleet police taxi" wiring. Look up in the 70--72-ish shop manuals, look up the optional 65A alternator wiring for the B bodies.

After I got out of the Navy (74) I saw a few Dodge ammeters melted from snow plow hoists, winches, or big driving lights. Looked EXACTLY like the photo in the MAD article, read it here:

Catalog

View attachment 1715603598
Click to expand...
Looks like I'm gonna have to do this Del! I was looking for my wiring issue and found this today. The two ends on the ammeter wires are melted off. They wasn't like that when I hooked them up.

20210128_144011.jpg


20210128_144019.jpg


20210128_144026.jpg


20210128_144036.jpg


20210128_144050.jpg
 
It only takes a split second. That's why I gave you the "warning" in your other thread. Its NEVER good, or to be looked at "later", it's an asap thing. Good catch!:thumbsup:
dartfreak75 said:
Yea me too. The car only ran for approximately 30-35 mins during break in too. That got hot fast!
Click to expand...
 
Mattax said:
What was the ammeter showing during these 30 minutes?
Click to expand...
Idk about the entire time because I was outside doing the engine break in but every time I looked it was max out at +40 the later I started it again and it kinda leveled out in the middle
 
dartfreak75 said:
but every time I looked it was max out at +40 the late
Click to expand...
There's the cause.
Sorry if I hadn't directed your attention to this some point in the past.
Also check the fusible link and the battery acid.
For future reference, the system will tolerate 20 - 30 amps for brief periods of time. Brief as in a minutes, but not 15 or 20 minutes. Pegging either direction is into danger territory, shut it off.

Charging Battery with Alternator - Warning
 
Sorry, just skimmed prior posts. If you run a bypass from ALT output to BATT+ as many do, your dash ammeter needle may still move, from the voltage drops in the wiring. All you really care is if the needle moves enough to show "charging" or "discharging". I went further in my 3 1960's Mopars, installing parallel-reversed diodes in series to give ~0.5 V drop at 50 A. I measured that w/ ammeter max'ed in the factory wiring, the voltage drop across the ammeter (and some wiring) is 0.75 V, so my new range is maybe 150 A (diodes are non-linear) which is more than any alternator I will install. Two of mine are 1965, which have dedicated buss-bars in the bulkhead connector so no melted terminals, and I mod'ed my 1964 to that. Search for my post "Modernized Wiring ..." or such from ~10 yrs ago for details, and ignore the fussing from posters who don't understand basic electronics.
 
GREAT info! I am in the process of rewiring the harness in the car (1969 Dart) I found many wires melted together and even the cursed aluminum foil wrapped around one of the fuses. The questions I have are three fold.
(1) if the ammeter should be bypassed, are you suggesting to connect the two with a connector?
(2) if so, wouldn't that negate the alt feed to the black wire?
(3) I put a 440 in the Dart and the alternator is from 1975, so I am thinking it is higher output than stock '69. Issues and concerns?
Thanks, FABO gurus.
 
If you're going to bypass the ammeter, just put both connectors on the same post, assuming it has the insulator in good shape. You can bolt the wires together, tape them good, and wrap them in insulation such as a rubber hose if you would rather. I'd have the alternator checked for it's output and get a regulator to match. I wouldn't use anything higher than about 60-65 amps with a stock '69 harness. If you have any high amperage draws, such as a high powered sound system, run a separate fused circuit for that straight to the battery.
 
Just bypassing the ammeter does nothing for the weak link, the bulkhead connectors.
 
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I don't know how you would bypass the alternator and still have a charging system :lol:. As for the AMMETER, that can be a problem area too,and that's what he asked about. If the bulkhead connector is in good shape, it'll handle 65 amps ok. Going higher than that and yeah, I'd run a separate heavier wire bypassing the main connector.
 
Generally the highest amperage draw on stock electric system is a discharged battery.
That's something an ammeter will show and a voltmeter will not.
Anything close to 40 amps into the battery is going to heat all standard connections. Of all the connectors from the alternator output to the battery, the Packard type push terminals are the weakest. When in the bulkhead there is less ability than other places for the heat to disapate.
The most straightforward solutions are the ones that copy some version of the factory optional wiring. (like shown above, or on this defrost grid equiped car)
edit: That's not to suggest that its good to charge a battery at 40 amps or more. Just that parallel wiring and/or not putting the entire load through the typical standard bulkhead connector will reduce problems with the circuit.
 
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