15 Volts

73Coupe

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I have the usual headlight dimming issue when at idle, so I thought I would start to work on that. Actually, all lights dim. Dash, dome, etc. Also, my radio reception is poor at idle, when I step on the gas, the static goes away and reception is clear again.
Previously, I had read this post on mymopar.com: MyMopar - Mopar Forums & Information - Mopar Headlight Dimming Issues

Here's how my system checks out...voltage at batt:
OFF: 12.8v
ON, Idle: 15.37 v (!)
ON, Idle, w/ everything on: 12.8-13.0v
ON, 2500 rpm: 15.37 v
ON, 2500 rpm, everything on: 15.67v
Positive voltage drop: 0.15v
Negative voltage drop: 0.002v
Field wire (green) ground test: good

Should it be around 14v?
Headlights still dim at idle! Despite 15 volts at batt.
Replaced regulator. Still 15+ volts.
Oh, and the dash ammeter doesn't move at all. Car off or on, any RPM. It always reads just a tad to the right of center. Isn't it supposed to move?

The FSM outlines a very detailed way to check the system, including using a carbon pile rheostat for placing a load on the battery. Where the heck does one get one of those? There must be a simpler way, right?

So, a call to expert advice out there...if anybody is well versed in the 'Ma' charging system of the early 70s.

Thx.....73
 
I would suspect ignition switch. You might have voltage drop there which would also explain higher charging voltage as the sense voltage to the regulator comes from ignition switch
 
I have the usual headlight dimming issue when at idle, so I thought I would start to work on that. Actually, all lights dim. Dash, dome, etc. Also, my radio reception is poor at idle, when I step on the gas, the static goes away and reception is clear again.
Previously, I had read this post on mymopar.com: MyMopar - Mopar Forums & Information - Mopar Headlight Dimming Issues

Here's how my system checks out...voltage at batt:
OFF: 12.8v
ON, Idle: 15.37 v (!)
ON, Idle, w/ everything on: 12.8-13.0v
ON, 2500 rpm: 15.37 v
ON, 2500 rpm, everything on: 15.67v
Positive voltage drop: 0.15v
Negative voltage drop: 0.002v
Field wire (green) ground test: good

Should it be around 14v?
Headlights still dim at idle! Despite 15 volts at batt.
Replaced regulator. Still 15+ volts.
Oh, and the dash ammeter doesn't move at all. Car off or on, any RPM. It always reads just a tad to the right of center. Isn't it supposed to move?

The FSM outlines a very detailed way to check the system, including using a carbon pile rheostat for placing a load on the battery. Where the heck does one get one of those? There must be a simpler way, right?

So, a call to expert advice out there...if anybody is well versed in the 'Ma' charging system of the early 70s.

Thx.....73


Here are a couple of things you can check:

1.) Check the chassis ground strap for corrosion or disconnect. A quick way to check this is to take a set of jumper cables and hook one lead to the negative cable on the battery. Hook the other end to a frame rail. Body should now be grounded, check your light function to see if there is any improvement.

2.) Check the wiring harness connector on the firewall for corrosion. Usually the connector block will have a small bolt that needs to be removed to unplug the harness from the block. Some versions will have push tabs that unlock the connector block. The big red wire in the connector block is the main power supply, check it carefully for corrosion or discoloration, the fusible link on most models will be in close proximity to the connector block, check it for damage such as melted insulation, If damage is noted, replace the fusible link wire.

3.) Your operating voltage is high, should never be over about 14v. Check the electrolyte level in the battery, a dry battery can show the symptoms you describe.

4.) The ammeter needle should move. These units were a pos from the factory and frozen needles were a common problem. They also had an annoying habit of shorting out and causing a dash fire from loose or corroded connections to the ammeter on the back of the instrument cluster. You can either go to an aftermarket ammeter or probably better, install a voltmeter as these do not generally have any short-out issues.

Hope this helps.

Dave
 
I have the usual headlight dimming issue when at idle, so I thought I would start to work on that. Actually, all lights dim. Dash, dome, etc. Also, my radio reception is poor at idle, when I step on the gas, the static goes away and reception is clear again.
Previously, I had read this post on mymopar.com: MyMopar - Mopar Forums & Information - Mopar Headlight Dimming Issues

Here's how my system checks out...voltage at batt:
OFF: 12.8v
ON, Idle: 15.37 v (!)
ON, Idle, w/ everything on: 12.8-13.0v
ON, 2500 rpm: 15.37 v
ON, 2500 rpm, everything on: 15.67v
Positive voltage drop: 0.15v
Negative voltage drop: 0.002v
Field wire (green) ground test: good

Should it be around 14v?
Headlights still dim at idle! Despite 15 volts at batt.
Replaced regulator. Still 15+ volts.
Oh, and the dash ammeter doesn't move at all. Car off or on, any RPM. It always reads just a tad to the right of center. Isn't it supposed to move?

The FSM outlines a very detailed way to check the system, including using a carbon pile rheostat for placing a load on the battery. Where the heck does one get one of those? There must be a simpler way, right?

So, a call to expert advice out there...if anybody is well versed in the 'Ma' charging system of the early 70s.

Thx.....73
I won't speak to your specif system as I have worked on them in the past, but wouldn't claim any particular expertise.

12 volt Alternators in general can charge above 15v if the battery is in poor condition. I would agree with Davea Lux above and check/fill the battery cells with distilled water and put it on a slow charge @ 2 amps until the voltage holds close to 12.68v (full charge). Then see what your charging voltage is. A good slow charge can desulfate an old battery enough to live a longer time. If you have another car with a compatible battery, you could just swap them for a quicker test.

I don't panic, but I start to wonder too when charging gets above 15v. Electronics in cars tend to die above 16v, which is the dangerous limit. On an older car with no electronics the symptom of light bulbs constantly burning out is often the first someone realizes they have this problem. Other electrical components can get damaged from too much current by this as well, Ohms law... if you up the voltage the current rises as well, so long as the load (resistance) stays the same.

As to carbon pile testers ... HF has cheap ones. The $50 one has an adjustment knob and a claimed 500 amp capacity, they have ones for half as much that rate 100 amps and use an on/off switch. I don't love them, but they are cheap and I have found them to reasonably durable in my environment where all tools get killed ASAP if not somewhat idiot resistant.
image_21239.jpg

If you go there, don't hold the load longer than recommended in your test instructions, for more generic testing we often just use the headlights and blower motor to provide some load.
 
you know how to check voltage drop. check it between a headlight (with them on and connected) and the battery. could determine if it's a ground or a hot side problem. my rule is 13.2 is the bottom, 14.2 is on the money, 14.5 is the top. over 14.5 starts to damage the battery.
 
Are you still running the stock alternator? The 12.8-13v at idle is the reason for the dimming lights. Test the things listed above and get back to us. Good luck:)
 
As suggested above, check the battery and all the connections.

I'm also going to suggest checking with another voltmeter before you go too much farther. Call it a "sanity check"... Over the years, I've seen too many meters that were not accurate.

Regarding your ammeter.... It's probably just not working... again, as said above. Assuming from your screen name that this is a 73 C body, the ammeter in your car is a shunt type. This means that the ammeter does not work like earlier cars were all the current passes through the ammeter. Only a small portion does. Simply stated, it's pretty much the same as the "MAD" modification where the alternator feeds the battery directly, except the factory did it for you.
 
I have the usual headlight dimming issue when at idle, so I thought I would start to work on that. Actually, all lights dim. Dash, dome, etc. Also, my radio reception is poor at idle, when I step on the gas, the static goes away and reception is clear again.
Previously, I had read this post on mymopar.com: MyMopar - Mopar Forums & Information - Mopar Headlight Dimming Issues

Here's how my system checks out...voltage at batt:
OFF: 12.8v
ON, Idle: 15.37 v (!)
ON, Idle, w/ everything on: 12.8-13.0v
ON, 2500 rpm: 15.37 v
ON, 2500 rpm, everything on: 15.67v
Positive voltage drop: 0.15v
Negative voltage drop: 0.002v
Field wire (green) ground test: good

Should it be around 14v?
Headlights still dim at idle! Despite 15 volts at batt.
Replaced regulator. Still 15+ volts.
Oh, and the dash ammeter doesn't move at all. Car off or on, any RPM. It always reads just a tad to the right of center. Isn't it supposed to move?

The FSM outlines a very detailed way to check the system, including using a carbon pile rheostat for placing a load on the battery. Where the heck does one get one of those? There must be a simpler way, right?

So, a call to expert advice out there...if anybody is well versed in the 'Ma' charging system of the early 70s.

Thx.....73

The only alternators that will put out a constant 14.3 - 14.7 are OE's with internal voltage regulation. You are lucky to hit that voltage with an externally regulated alternator just by virtue of the length and condition of the wires that bridge them not to mention the rest of the electrical system. Today's remaned, rewired, souped-up high output alt's are not built to spec's like the OE's. Internal wire windings are gauged according to cost and profit, brushes can be of inferior material and even the amount of magnetic bars on the armature can be different from brand to brand. If you think you have an output problem, wire your alt and regulator directly to battery completely ommiting the rest of the cars wiring including the ignition switch. Ground directly to the battery and pull your 12 volts directly from the battery with your charge going directly back to battery positive. Diagrams are available online and fortunately Mopar charging systems are the simplest of all manufacturers. Then take your output readings with the battery as the only load. Trust me, you'll be completely surprised at what you find even with a fully charged battery. Then, and only then will you know the state of your alternator.
 
Thanks for all the info, this is great advice, and I appreciate it!
The alternator is the one that came with the car, and I'd assume it's not the original one.
My multi meter is new, digital, and auto range. It checks out just from using it on other cars and using on building electrical.
The battery is about a year old from NAPA. It's a sealed type, I don't think I can open it up to check levels, but I will look again.
Overall this car's wiring is in pretty good shape and all original. I've never had the bulkhead connector apart but will check that first and clean it.
 
Here's the battery. Can these tops be opened? I have never wanted to deliberately attempt to open them.

IMG_2257.JPG


This is the only suspect looking part of the wiring. See the crimp splice? Somebody removed a faulty connector in the past and replaced it with this. This is on the big current carrying wire from the alternator. This shouldn't explain the high voltage reading, though, should it? Anyways, I should check the resistance of this wire from end to end. I plan to solder this splice anyway.

IMG_2258.JPG
 
Can these tops be opened? I have never wanted to deliberately attempt to open them.

They can be opened. See the little notches? That's where you can put a screwdriver in and carefully pry.

This is the only suspect looking part of the wiring. See the crimp splice? Somebody removed a faulty connector in the past and replaced it with this. This is on the big current carrying wire from the alternator. This shouldn't explain the high voltage reading, though, should it? Anyways, I should check the resistance of this wire from end to end. I plan to solder this splice anyway.

This would have no bearing on too much voltage. Honestly, I don't think this splice is a problem, but it can't hurt to fix it.

What I do see is some possible issues with the battery terminals, especially the negative terminal. See how there's no gap where they clamp? Those terminals are stretched to the point of where they aren't clamping on the post. While that may not be the issue, it's something that you want to correct.
 
Update (finally):
I checked the battery, water was not low but I added a couple squirts of distilled to each cell to ring it up a little.
I replaced the alternator with a rebuilt 60 amp Remy unit a few moths ago and that seemed to solve the low voltage issue at idle. Headlights now stay bright. They dim very slightly at idle, but nothing like before.
I also fixed the bad splice in the 10 gauge wire with a soldered in splice, made no difference.

I checked the bulkhead connector and it was pristine. I cleaned it anyway and packed it with dielectric grease.

Then I got a new batt neg cable from Evans and installed it.

Still 15 - 15.5 volts at the battery, post to post. Grounding the regulator made no difference. But then I checked the Sun tuneup card for this vehicle and it specified a slightly different method for checking the operating voltage regulation: "Voltmeter connected to pos. lead on regulator IGN No. 1 terminal of ballast resistor (blue wires), neg. lead to good ground.
At 80F, volts min: 13.8, volts max: 14.4, and shouldn't exceed that by 0.5 V.

With this method it checked out at 14.47 V. Problem solved? I'm optimistic. I'm experiencing no negative electrical symptoms at all. Car is completely reliable and I still drive it 200 miles per week with no incidents.

IMG_5292.jpg


IMG_5287.jpg


IMG_5291.jpg
 
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Well I still think you have a voltage loss on your ignition switch. Therefore you have over 15 volts at battery posts and roughly 1 volt less at the blue wire coming from the switch at ballast resistor.

The regulator senses the charging voltage from that blue wire and now that you have voltage loss there the actual charging voltage at battery post is the amount of voltage loss higher.

I had same thing in my Challenger. Roughly 15.5 at battery and 14.3 at regulator sense/that blue wire. Destroyed my expensive AGM battery before I noticed the problem. Had super bright head lights though as I have relays feeding the lights directly from the battery.

New ign switch and now I have less than 0.1 volt higher charging voltage at the battery when compared to the regulator sense
 
Well I still think you have a voltage loss on your ignition switch. Therefore you have over 15 volts at battery posts and roughly 1 volt less at the blue wire coming from the switch at ballast resistor.

The regulator senses the charging voltage from that blue wire and now that you have voltage loss there the actual charging voltage at battery post is the amount of voltage loss higher.

I had same thing in my Challenger. Roughly 15.5 at battery and 14.3 at regulator sense/that blue wire. Destroyed my expensive AGM battery before I noticed the problem. Had super bright head lights though as I have relays feeding the lights directly from the battery.

New ign switch and now I have less than 0.1 volt higher charging voltage at the battery when compared to the regulator sense

Thanks. I at least enjoyed a brief stint of ignorant bliss over the weekend, though, lol.

I'll have to study my wiring diagrams some more, they are hard to read. Do the blue wires come directly from the Ign switch? I have never messed with the switch, perhaps if I remove it and clean it , might fix the problem? Otherwise, I'll imagine that a new switch is hard to come by for this car.
 
Thanks. I at least enjoyed a brief stint of ignorant bliss over the weekend, though, lol.

I'll have to study my wiring diagrams some more, they are hard to read. Do the blue wires come directly from the Ign switch? I have never messed with the switch, perhaps if I remove it and clean it , might fix the problem? Otherwise, I'll imagine that a new switch is hard to come by for this car.

Here is a link for a '72 Chrysler color wiring diagram from Classic Car Wiring. Although they do not show a diagram for a '73, the '72 might suffice. Get the BIG one:

1972 Chrysler Color Wiring Diagram
 
Thanks. I at least enjoyed a brief stint of ignorant bliss over the weekend, though, lol.

I'll have to study my wiring diagrams some more, they are hard to read. Do the blue wires come directly from the Ign switch? I have never messed with the switch, perhaps if I remove it and clean it , might fix the problem? Otherwise, I'll imagine that a new switch is hard to come by for this car.

The blue wire should come directly from the ign switch. The switch itself would be pretty tricky to disassemble for cleaning though it is possible. At least on mine, the end plate with the contacts has bended tabs over it and the tabs are so thick that I think that they would break if tried to straighten up.

I got my new switch from rockauto for 25 eur (about 30 usd). Apparently same switch has been used on c bodies without tilt wheel so if your car does not have tilt wheel then you could get new switch quite easily.

For temporary "fix" you could run separate wire with toggle switch directly from battery to the voltage regulator. That's what I did for the previous summer and fixed it during winter. Just remember to cut the power to the regulator when not driving or it will drain your battery.
 
Good read... glad you got it fixed. Two of my previous 73 Town and Country Wagons had the same issue with that connector. They get loose and overheat cutting power off to the harness from the alternator. No bueno.
 
The blue wire should come directly from the ign switch. The switch itself would be pretty tricky to disassemble for cleaning though it is possible. At least on mine, the end plate with the contacts has bended tabs over it and the tabs are so thick that I think that they would break if tried to straighten up.

I got my new switch from rockauto for 25 eur (about 30 usd). Apparently same switch has been used on c bodies without tilt wheel so if your car does not have tilt wheel then you could get new switch quite easily.

For temporary "fix" you could run separate wire with toggle switch directly from battery to the voltage regulator. That's what I did for the previous summer and fixed it during winter. Just remember to cut the power to the regulator when not driving or it will drain your battery.

Had time to test this the other day and sure enough...
I ran a jumper between the battery positive and the blue wire on the ballast resistor.

With jumper, 14.9 v @ battery, 14.9 @ ballast.
Without jumper, 15.6 @ battery, 14.7 @ ballast.

I will probably look for an nos ignition switch.
 
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