68 Dart wiring questions

[demon322]

We are working on my uncles 68 Dart. For now just trying to get it running and moving before we worry about what’s ‘correct’.

My first question is can I use an alternator with 2 (I assume) field terminals when his car only has wiring for one (green.) I have that alternator and we are hoping to have a charging system while we try to keep the motor running long enough to tune on it a bit.

 

[HemiSSDart]

Yes, you have to ground one terminal to the chassis. I used to run a wire over to the inner fender where there was a hole drilled before I got it.

 

[Dana67Dart]

Typically this hole is tapped. Green cir on the alt body

You can run a ground wire from either of the terminals to the screw you can add to the tapped hole.

One terminal will line up with the OEM wiring harness better than the other.

I would double check that both field terminals are isolated from the housing.

In your photo it looks correct for an isolated field alt.

 

[Mattax]

We are working on my uncles 68 Dart. For now just trying to get it running and moving before we worry about what’s ‘correct’.

My first question is can I use an alternator with 2 (I assume) field terminals when his car only has wiring for one (green.) I have that alternator and we are hoping to have a charging system while we try to keep the motor running long enough to tune on it a bit.

View attachment 1716207818

See this post, but I think it will stick better if you read from the top post.

Identifying Chrysler Alternators (1960-1976)

Roundback and Squareback refer to the style of housing. Roundback through model year 1969. Roundback for model years 1970-71 usually has a slightly different rear housing Squareback Revised Squareback Is most easily differentiated by the thin middle between the housings. Overall these...

www.forabodiesonly.com

Begin with a charged battery and make sure there isn't any high charging or discharging of the battery.
Monitor the ammeter when the car is running.
Someone here in recent memory fired up a new engine with a battery that needed charging.
The alternator worked great, so provided over 40 amps during the break-in. The owner saw the high charging on the ammeter but didn't understand the importance. After 20 minutes all the connections were melted.

 

[demon322]

Typically this hole is tapped. Green cir on the alt body

You can run a ground wire from either of the terminals to the screw you can add to the tapped hole.

One terminal will line up with the OEM wiring harness better than the other.

I would double check that both field terminals are isolated from the housing.

In your photo it looks correct for an isolated field alt.

The circled hole is not tapped. Neither are the other two. Here are close ups of the two field terminals

 

[demon322]

See this post, but I think it will stick better if you read from the top post.

http://[URL]https://www.forabodieso...-alternators-1960-1976.475691/post-1973173813

[/URL]

Begin with a charged battery and make sure there isn't any high charging or discharging of the battery.
Monitor the ammeter when the car is running.
Someone here in recent memory fired up a new engine with a battery that needed charging.
The alternator worked great, so provided over 40 amps during the break-in. The owner saw the high charging on the ammeter but didn't understand the importance. After 20 minutes all the connections were melted.

A lot of good info here! But this also leads me to another question I have. There is no ammeter currently as the dash cluster is out. I have attached and taped the red and black ammeter wires together for now but as I understand it the true ‘bypass’ involves more than that

 

[Dana67Dart]

The circled hole is not tapped. Neither are the other two. Here are close ups of the two field terminals

You could tap one of them just be sure you do t get chips into the guts if the alt.

Or just run a ground wire to a good ground anywhere accessible.

 

[MadScientistMat]

A lot of good info here! But this also leads me to another question I have. There is no ammeter currently as the dash cluster is out. I have attached and taped the red and black ammeter wires together for now but as I understand it the true ‘bypass’ involves more than that

That fully bypasses the ammeter. Some wiring installations try bypassing more than that, such as the feed-through connection on the bulkhead. There are some websites with directions that just drill through the connector and run a wire through that, but I'd recommend something more readily disconnectable, like a bolt run through a grommet with ring terminals on each side.

 

[Mattax]

That fully bypasses the ammeter. Some wiring installations try bypassing more than that, such as the feed-through connection on the bulkhead. There are some websites with directions that just drill through the connector and run a wire through that, but I'd recommend something more readily disconnectable, like a bolt run through a grommet with ring terminals on each side.

Or just don't do it.

 

[MadScientistMat]

Or just don't do it.

Fair enough, I'm not convinced the bulkhead bypass is necessary. But a badly done bulkhead bypass is the worst possible option.

 

[Mattax]

Fair enough, I'm not convinced the bulkhead bypass is necessary. But a badly done bulkhead bypass is the worst possible option.

I agree 100%.
Its really the ammeter bypass that I think is mostly unneccessary - but your point is exactly what I've been observing. People are encouraged to make changes they don't understand and most of all don't have the skills and tools to do well.

 

[Dana67Dart]

Leave the OEM wiring alone and add a heavy gauge wire from the alt output to the batt stud on the starter relay.

Might want a fussble link or fuse to protect the wires.

It will bypass the bulkhead connector and as a bonus split the current needed to run the car in half on the existing bulkhead connectors.

 

[Mattax]

No it won't. Only battery charging gets bypassed with a direct wire. Current still needs to go through one or the other feed at the bulkhead to run everything else. How well this works depends on the execution. It also leaves the operator without a way to judge system operation. So then a voltmeter is needed.
And without a fuse or fusible link, a short in the alternator will be a serious burn. Now with two fusible links and two paths, a short will burn twice as long. All for what? Sometimes there is a reason, but most the time people are best off just finding problems and fixing them. That's difficult enough for someone whose not done it before. How many tmes do we see people post correct splicing, crimping methods, tools and connectors? How many more times do we see the cheapest closed barrel terminals badly crimped with conductor exposed, etc?

For a long time I was pushing a headlight relay harness as a win-win for reducing loads on the main feeds going through the firewall, the headlight circuit, and improving the headlight power. But with Rob not making them at the moment, I don't know of off the shelf good ones to recommend. Dan Stern sells kits with quality parts, but its project that has to be done reasonably well.

 

[Dana67Dart]

Only battery charging gets bypassed with a direct wire. Current still needs to go through one or the other feed at the bulkhead to run everything else

That's what I was trying to get at.

In stock form the alt goes through a bulkhead connector to the Ammeter then Back out through a bulkhead connector to the battery

Along the way it gets tapped into to run the car

By leaving the cars OEM wiring in place the current to run the car gets shared by 2 bulkhead connectors halving the current on each

Adding the alt to battery post on the starter relay wire the battery charging current stays out of the bulkhead connectors (mostly)

It's a form of MAD bypass

A fuse on the bypass wire should protect the car from an alternator short.

Once that fuse blows the rest of the cars wiring should work as designed and the fusible link would be next.

At least that's how I see it.

 

[Mattax]

It doesn't get shared. People who have done the wire around report the ammeter shows no charging, but does show discharging during start up (or when the alternator dies). This proves electricity takes the route of least resistance, which is usually the shortest path.
It's better than the insanity but usually not neccessary.
What situation cause the battery to demand high current? And when those situations occur, should the driver know about them?
I can't answer that for others. But I think people should know that this is not a win-win. It's a tradeoff.

The fuse is also a tradeoff. it needs to be sized for the wire, but which wire? Normally one sizes for the smallest wire one wishes to protect.
What size fuse is needed to protect a 12 gage wire? But will that be too small to survive the short periods of high charging that can occur in normal operation? IDK. Lets look it up.

edit: here's what one person or group came up with, and extrapolating from it,
16 gage fusible link would be replaced with something between 60 and 80 amps.
---
With the bluesea calculator, using worst case normal use as 25 amps for 20 minute, and no more than 8' of 12 ga wire, the fuse should be at least 31 amps. The closest glass fuse is probably 40 amp slow or fast. So I think that your scenario that the fuse goes quick and then the fusible link does it normal time to burn out is reasonable. The actual seconds it adds to the burn is probably not a lot. (That's not a recommendation to anyone reading, just an opinion)

 

[demon322]

Thanks again for the replies and info. The main reason I did the ammeter bypass like I did was that we don't have a dash cluster for him at the moment and I knew it wasn't safe to have the red and black ammeter wires lose in the dash so I connected them with a small bolt and taped it really well. Down the road I will look for a better and more permanent solution. As for monitoring charging for now, I will hook up a voltmeter from the aftermarket 3 gauge set we are using currently to monitor oil pressure and coolant temp once I get the alternator working.