High charging, but new interior harness?

[mtldart]

So I am at a loss here.
1974 four door dart, automatic, with air conditioning. I have had it since October, it was in winter storage all winter long and I just got it out last week and am ready to start tackling spring projects.
I have been reading up about all kinds of stuff and wanted to swap out the ammeter for a voltmeter because of the risk of old wires and fires and all that. was hoping to do it in the dash without having to remove a bunch of stuff, which seems impossible. that aside, I am planning on installing a pretty substantial stereo system so I also wanted to eliminate that fire hazard behind the dash with the ammeter. well I finally got to look behind there today and it almost looks like the entire harness behind the dash is brand spanking new!? in which case, I am not worried about that ammeter being there at all. Looks like modern connections to the ammeter with more than ample/supple wiring. when I look at the connection in the firewall, I don't have the spade connectors where the ammeter wires come through, it looks like its a molded rubber wire/fitting.
now here's my dilemma, the car is charging at 15.1/15.2 volts. Everywhere I have read on here is saying "WHOA THATS TOO HIGH" so in theory I have a voltage loss somewhere, except I can't for the life of me find it. If the harness is all new under the dash, I have a hard time imagining thats where the problem lies at that "spliced connection" that the MAD electric folks tell you to find.
I will be replacing my alternator for a 100amp alternator to make sure I still have battery power once I install my stereo. my current alternator sounds like its got a bad bearing in it anyways, so it needs to be replaced.

My question is could a bad alternator be making my car charge that high? I assumed the voltage regulator would keep it from doing that, but maybe im wrong. It's reading the same power at the alternator as it is at the battery. Previous owner put a new voltage regulator and new ignition and all kinds of other stuff in there too. the wiring harness in the engine bay is typically dirty, but doesn't look molested with any weird splices or cuts or anything that looks out of the ordinary.

i have attached two pictures, one is of the connection at the ammeter with what looks like very fresh wiring, and then a second which is according to the part number a "seatbelt control interlock module " (which i have no idea what that does, but also shows its all new wiring back there). i couldnt trace the two wires for the ammeter very far, they go up and into the dash and are nice and ziptied and taped, and since it all appears to be new pulling the dash seems foolish. in this case.

yall got any input or advice here?
im not sure how to figure out why its charging at over 15, im also not sure if its a huge problem, but I have this feeling the alternator is the reason, but is that even possible?

thanks for any help!

 

[Demonic]

it was in winter storage all winter long

maybe it is just charging high from sitting? Unless you had a good trickle charger on it.

 

[mtldart]

well i pulled the battery over the winter and kept it topped up in my living room.
I've driven about 200km since i pulled it out (this lockdown had made it semi-illegal to go for cruises here in quebec). Now every single time i take the volt reading is within a few minutes of starting it. do they charge at 15 volts, then after driving for 30 minutes or so come back down to a regular number? I didn't even think about that. This is my first classic car so I am still very much learning.

 

[MoparLeo]

Remember that a when brand new the harness wasn't designed for more than 60 amps.
Improved Wiring for older Mopars

 

[mtldart]

ya know. the more I dig into this it looks like someone beefed it up for higher amps, it has what appears to be all that work done in that article already done to it. also, the stereo im installing will be on its own wiring system (like it should be) but entirely underneath a 60amp fuse.

 

[Mattax]

well i pulled the battery over the winter and kept it topped up in my living room.
I've driven about 200km since i pulled it out (this lockdown had made it semi-illegal to go for cruises here in quebec). Now every single time i take the volt reading is within a few minutes of starting it. do they charge at 15 volts, then after driving for 30 minutes or so come back down to a regular number? I didn't even think about that. This is my first classic car so I am still very much learning.

1. That's pretty normal. Look at the shop manual and you'll see the 'cold' voltage regulation range goes to 15. Temperature of interest is the temperature by the regulator.
2. After starting, the current flowing from the alternator is higher than after you've been driving. I'm going to let you think about why that is. The higher the current through any resistance(s), the more the voltage drop.

so in theory I have a voltage loss somewhere, except I can't for the life of me find it. If the harness is all new under the dash, I have a hard time imagining thats where the problem lies at that "spliced connection" that the MAD electric folks tell you to find.

I don't care what MAD says. They make sweeping generalizationsand have some poor advice. The problems are usually at the various connectors, especially the bulkhead and steering column (70-75) that carry higher currents. The main splice rarely is weak connection.

 

[Mattax]

I'm going to let you think about why that is.

Photo essay here and explanation in the post above it. Charging Battery with Alternator - Warning

The higher the current through any resistance(s), the more the voltage drop.

So what you can do is use a voltmeter to measure the voltage drops right after starting. Because of your intended addition to the system, its a good check to make at this time.

Even though you may not see where the wire goes, thanks to the wire diagrams in the Factory Service Manual, we know where they connect - almost.

I don't have the spade connectors where the ammeter wires come through, it looks like its a molded rubber wire/fitting.

Take a photo of this and the firewall. Chrysler used molded rubber grommets through the firewall for various circuits depending on the year, model, and option. It's possible yours has the battery feed coming through the grommet to the ammeter and then back out the grommet to a terminal post where it joins the alternator output and feeds back through the bulkhead connector. This was one of the optional arrangements.

The more typical power supply scheme was like this.

On this one you can measure the drop in voltage from:
alternator output (BATT terminal) to starter relay, and the current flow to the battery seen by the ammeter.
alternator output to alternator field terminal with the blue wire, as well as at the ballast resistor.
Measuring the voltage to ground at ballast resistor and field terminals will give a pretty good sense of what voltage the regulator at the sense connection.

 

[mtldart]

I was worried that was the case with cold voltage. Thanks for that, I am waiting on the 1974 service manual to come in the mail any day specifically so I can reference stuff like this.

 

[67Dart273]

DID YOU ACTUALLY CHECK BATTERY VOLTAGE with a voltmeter?

By that I mean actually right at the battery posts? If that is where you read the 15+V then it is "a bit" too high, but not REALLY BAD.

It is most likely that kind of voltage is a result of system voltage drop, a subject I've written about more than numerous times

 

[mtldart]

Yes I checked it with my voltmeter with car off, key on and running.
I also tried to find any voltage drop with the key on at the various spots and couldn't really find any major drops.

Will go through the options @Mattax listed in the last post there.

I guess it should be noted when I first start the car it goes from 13.8 and slowly works up to 15.1. I will also take a drive tomorrow and see if as the engine bay warms up the voltage regulator starts bringing it down a bit.

 

[Mattax]

Will go through the options @Mattax listed in the last post there.

A grommet for the battery feed should be fairly obvious. The wires I see going to your ammeter only look to be typical 12 ga automotive. I'm going to guess that your car has the standard main harness wiring - same or similar as diagrammed above. Grommets were also used for a/c wires and sometimes for gages-senders.

 

[mtldart]

ah yeah, its not a grommet through the firewall. its a rubberized piece that is at the end of the fusible link that goes directly into the firewall through one of the three plugs with all the wiring. I will take a picture of what I am talking about.

Remember that a when brand new the harness wasn't designed for more than 60 amps.
Improved Wiring for older Mopars

if I do this do I just put it right there on top of the original wires that are hooked into the ammeter and its just an additional thing to clamp down with the nut?


thank you everyone for your help, i appreciate it. i've read through a ton of info about voltage drop and everything to try to figure this out on my own and was just really thrown off by what appears to be a brand new harness under the dash.

 

[Mattax]

ah yeah, its not a grommet through the firewall. its a rubberized piece that is at the end of the fusible link that goes directly into the firewall through one of the three plugs with all the wiring. I will take a picture of what I am talking about.

The molded insulation is just the standard way those terminals were done. The ring terminals on the starter relay and the alternator will have also be done that way,

if I do this do I just put it right there on top of the original wires that are hooked into the ammeter and its just an additional thing to clamp down with the nut?

That article has the one of the optional wiring concepts, but the execution recommended is pretty bad.
Yes you can a second alternator output feed wire and connector to the ammeter stud on top of the existing ring terminal.
It is not a negative terminal.
Do not use a squeeze connector. The whole idea is to increase the current carrying capacity and those are terrible connectors for that.
Don't go through the speedometer cable grommet. Use a dedicated grommet.
Ring terminal to ring terminal. If a connector is desired in between, use one with lots of surface area.
What you do for the stereo depends on how it will be used. if its only going to be used while driving, power can be taken right from the alternator. But if its going to be run with the car off, then look at what was done for cars running rear defroster. Like this How rare is electric rear defrost?
Another step you can take is to add a headlight relay harness. This diverts the 9 plus amps directly to the headlights further reducing the current into the car.

 

[mtldart]

i don't like the idea of squeeze connectors. I prefer to crimp, solder and shrink wrap whenever possible. Im used to working on motorcycles where you can't really use just a crimp or it will all vibrate into nothing.

yeah, the stereo will be used only while driving, it will be a high powered stereo, but I am not the kind of guy to sit in a parking lot or car show playing tunes. I actually bought the LED headlights to bring down some of the power draw for those (and one of my headlights burned out so it was a good excuse to replace both)

thanks again for all this information, really appreciate it!

 

[Mattax]

Since it won't be drawing down the battery, then you could run the parallel wire and share it with all equipment (attach at the ammeter) or run a dedicated stereo line. eitehr way works.
Link to the defroster/60 amp option added to my post above. Nice thing about that set up (IMO) is only one fusible link is needed.
I'm actually adding a very similar wiring setup to my car. I'm going to use a terminal post on the firewall because that will allow the MSD 6T to draw power from the correct side of the ammeter. It's minor but will make me feel better knowingthe ammeter is only showing battery charge/discharge. It also is what is shown in the factory assembly drawings, although there is no other evidence it was ever used on an a-body that early.

 

[mtldart]

so I figured I would post here in case anyone ever comes across this problem.
I took out my instrument panel to install a new speaker and when i did that i made sure to clean up all the connections back there, just because. so any plug has been cleaned and dielectric greased and everything was put back together.
I also took my alternator to an alternator shop and had it rebuilt, my stator was all burnt out and maybe some connections were dirty....who knows.
Just installed the new alternator, and the high charging problem is now gone! Maybe there were some corroded connections at the alternator, maybe behind the dash. I had also as part of the trouble shooting cleaned up the ground to the battery, and to the voltage regulator but those didn't change anything before.

soooo, it was either the alternator being bad (my suspicion) or a bad connection that i cleaned up when i put everything back together to install the new speaker.