Voltage Gauge Spiking

[quickgraffix]

My 69 is having electrical issues when im @ idle the gauge is calmly sitting in the middle but when i add any type of throttle it spikes to the max amd one of my wires started smoking (main wire from alternator) need help guys

[martincom]

Which direction does it spike, toward charge or discharge?

[quickgraffix]

Which direction does it spike, toward charge or discharge?

Charge

[Wildergarten]

My 69 is having electrical issues when im @ idle the gauge is calmly sitting in the middle but when i add any type of throttle it spikes to the max amd one of my wires started smoking (main wire from alternator) need help guys

You probably have more than one problem.

The '69 was the first year to use a molded 'multiplug' firewall connector with Packard style lugs latched into both male and female elements. These connectors are rated at 30 amps. It is not uncommon for owners to replace the stock alternator with one rated at twice that.
Dodge used #10 wire for the alternator leads, which is WAY undersized for that current. That means if your regulator switches the alternator to put out full bore, those wires will heat up. The molded plug is a great way to go because it is so easy to add features or make changes, but it is current limited. If you do need a new one because of this mishap, they last time I looked they were still available new on ebay but at a cost of $80.

The alternator wire is bundled into the harness in such a way that it doesn't get rid of heat efficiently. If it does get too hot, the insulation can fail, usually at the connector but I've seen it elsewhere under the dash. Once that happens, you'll need to tear down the harness and excise all the wire that is toasted by the problem. Needless to say, that could be a lot of damage, and it often is. If there's a short as a result, that's why the current pegs.

My advice would be to pick up a couple of marine-grade bulkhead connector studs and run the alternator line to one and the return through a second stud line from the ammeter to either the battery or the fat lug on the starter relay (electrically the same thing). Basically, remove the charging loop from the harness entirely and run it through #6 or #8 THHN or MTW wire with the corresponding ring lugs. If you want to be safer, put a fuse inline, and again I'd go with marine grade. Blue Sea Systems has great products, and once you see them, it's easy to judge a cheaper alternative in a search.

Finally, I'd pull the mechanical regulator for an electronic one unless you're into keeping it paleo for EMP reasons.

[martincom]

Wildergarten makes good points. However, as your truck is a '69, it would have the mechanical regulator and I doubt if it has the 60 amp alternator. Even if it did, unless you have added some high current demand aftermarket components, you'll never draw 60 amps out of it. I have a 60+ amp alternator on my D100 and do not have issue with my stock wiring configuration.

That being said, the capacity of the vehicle wiring has nothing to do with your problem. My first reaction is your regulator is defective. However,let's run another test before we blindly start replacing parts. Unplug the field wire (1/4 slip-on terminal) from the back of the alternator. This will disable the alternator. Start the engine and rev the truck as you had before to duplicate the trouble. Is the wiring that was beginning to smoke before getting hot?

If not, you probably have a defective regulator. If the regulator has failed, the battery would be exhibiting signs of being overcharged. You'd smell electrolyte vapors and the top of the battery would be wet from electrolyte vapors condensing on it. The cheap fix is to replace the regulator. A better fix would be upgrading to an electronic regulator. I believe there is some aftermarket electronic regulators designed to replace the mechanical regulator.

If the wiring is still getting hot or beginning to smoke, you have something shorting to ground between the battery and the battery side of the alternator gauge. Probably something getting pinched from the torque roll of the engine when revved up. Check the heavy lead from the starter relay to the starter motor.

[Wildergarten]

Wildergarten makes good points. However, as your truck is a '69, it would have the mechanical regulator and I doubt if it has the 60 amp alternator. Even if it did, unless you have added some high current demand aftermarket components, you'll never draw 60 amps out of it. I have a 60+ amp alternator on my D100 and do not have issue with my stock wiring configuration.

The new 30 amp original equipment equivalent alternator on my last '68 truck couldn't keep up with the combination of lights, wipers, and defroster. I can easily see people getting tired of that, going to the parts store, and having the guy at the counter sell them the bigger '75-'87 alternator, as it's a bolt-on. I did. When I bought my current '68, the alternator line had been replaced with a new bypass through the firewall, as did my '67 camper special. The '68 already had the electronic regulator; a previous owner apparently got tired of the fusable link inside the mechanical regulator. I've repaired so many of those I couldn't count them. My '69 had the melted firewall plug I mean to replace along with a harness that had wires melted together. I do have a couple of adjustable mechanical regulators, and those are far better made and less likely to spike the system with cyclical 'full-on-or-off' behavior typical of the early system.

The page at this link discussing early Chrysler electrical systems including the firewall connector in your '69 is very good: https://www.allpar.com/threads/taking-c ... 1085245456
There's a good thread on this site here: viewtopic.php?f=21&t=34977&p=254332&hil ... ts#p254332
The connectors are available here: https://www.megapartsusa.com/products.php?cat=749

[martincom]

The OEM small alternators were rated at 40 amps, not 30. For the vehicles of the time, they had more than enough capacity to keep up with the load of wipers, headlights, defroster fan, etc. Often folks thought they could not because they would almost always indicate and did discharge at idle. This was not a capacity issue, but an inherent design limitation of the mechanical regulator.

Back in the days when dinosaurs roamed the earth, according to my daughters, and the typical high school age male had at least 350hp under the hood, it was the latest greatest thing to ditch the all famous dual point distributors for electronic ignition. In fact, Chrysler's Direct Connection program offered a kit, with a complete distributor, at a very affordable price. One of the installation per-requisites was a constant output alternator/regulator combination---which anything before 1970 was not. The reason was the mechanical regulator/alternator combinations had little to no output at idle. In turn, the voltage would drop and the electronic ignition would begin to miss as a result.

I'll agree the bulkhead connectors were barely adequate, but none the less adequate as built. However, factor in some corrosion and that changed. I never encountered much trouble with them melting. The voltage drop across the poor connection would show up much sooner with dim lights and other issues. Melted bulkheads were almost always a secondary failure to improper wiring that first took out the fusible link. Of course, it was replaced with standard wire and with that, the protection. Then the bulkheads melted and often the entire vehicle.

The terminals for the bulkhead are readily available and affordable. If there is a corrosion issue, they should be replaced. Cleaning them is a short term remedy, as the corrosion has likely destroyed the plating and they will quickly oxidate. Also, the bulkhead has a number of empty ports with the third section being totally vacant on trucks. If you have a high demand aftermarket electrical load you can up size the alternator output wiring and/or feed it through two or more bulkhead connections in parallel, doubling or tripling the current capacity while still maintaining the stock appearance, no added holes in the firewall, a sealed pass thru, and maintaining the ease of servicing disconnection point.

[Wildergarten]

The OEM small alternators were rated at 40 amps, not 30.

What's your source for that? The article I cited says 30. https://www.allpar.com/threads/taking-c ... 1085245456

I'll agree the bulkhead connectors were barely adequate, but none the less adequate as built. However, factor in some corrosion and that changed. I never encountered much trouble with them melting.

In the '69, I was running a flatbed with extra clearance and running lights. Remember too that I short-hop my truck about our property, sometimes running it only a few feet loading brush. That alternator wasn't adequate and when it tried to be, things got warmer until it was eventual smoke city.

The voltage drop across the poor connection would show up much sooner with dim lights and other issues.

Like undersized wiring. 40A at 12VDC in #10AWG pvc coated wire is not OK. In ten feet from the alternator to the ammeter and back, the drop is nearly a volt, and that's without the loss at the bulkhead connector. https://www.powerstream.com/Wire_Size.htm This chart at Blue Sea Systems shows that 30A is all that size will take without big losses. http://assets.bluesea.com/files/resourc ... hartlg.jpg

Melted bulkheads were almost always a secondary failure to improper wiring that first took out the fusible link. Of course, it was replaced with standard wire and with that, the protection. Then the bulkheads melted and often the entire vehicle.

Bad design, probably driven by manufacturing engineering looking to cut costs. The philosophy was rampant, which is why the castings take so much work to clean up.

The terminals for the bulkhead are readily available and affordable. If there is a corrosion issue, they should be replaced. Cleaning them is a short term remedy, as the corrosion has likely destroyed the plating and they will quickly oxidate. If there is a corrosion issue, they should be replaced. Cleaning them is a short term remedy, as the corrosion has likely destroyed the plating and they will quickly oxidate.

The Packard connectors and that bulkhead socket are great as long as the alternator line is removed, vastly better than the molded rubber Molex style that preceded it. It's what I'll be using on my build. The connectors in the bulkhead fitting are NOT easily replaceable up under the top left corner of that dash. Mine were not plated but solid brass (made by Delco). Worse, both the two female lugs for the alternator in that connector body and the two lines in the plug had rubber boots over the wire fitted tightly in the socket. I'm guessing they were supposed to help insulate the lugs from melting the connector body. As far as I know, those molded rubber coated lugs are irreplaceable and anything else will transfer the heat from contact resistance directly into the nylon.

Also, the bulkhead has a number of empty ports with the third section being totally vacant on trucks. If you have a high demand aftermarket electrical load you can up size the alternator output wiring and/or feed it through two or more bulkhead connections in parallel, doubling or tripling the current capacity while still maintaining the stock appearance, no added holes in the firewall, a sealed pass thru, and maintaining the ease of servicing disconnection point.

I won't be doing that because I'm making a work truck, not a restoration, with so many lines, so far, that it looks like I'll be pressed to get it all in that connector body using all three ports. So in that case, form follows functions: twin batteries, an isolator, bulkhead studs and a regular fuse instead of a fusable link. There will also be 120VAC in a flex conduit running under the body through the back cab panel to a trickle charger and from the inverter, also under the passenger-side seat. The 120V connector is under the bottom of the front bumper for the trickle with shields to protect the wiring from the chain in the chain boxes. The real peril with all that is that I will have to remember to pull the plug before getting in the truck, the unfortunate habit being that I do get in a hurry.

[martincom]

Mark, we're not talking about the man's problem and our bantering back and forth about design criteria is probably only confusing the issue. His problem has nothing to do with the capacity of the wiring or the connectors. Let's help the fellow.

[Wildergarten]

Let's help the fellow.

I did. You took issue with the recommendations. I gave you my reasons, and it drifted from there. I don't write these things just for this thread, but because people use search to learn about these trucks. Hopefully, the combined exchange will serve multiple people's purposes, whether they want a stock repair or an upgrade. The conversation served both purposes, no offence taken or intended.

[PwrWgnDrvr]

The (1966) and 1970 Truck FSM's list 3 alternators in the specifications section, pg 8.
They are:
(35) 37 Ampere Alternator - output 34.5A
46 Ampere Alternator - output 44A
(59) 60 Ampere Alternator - output 51A

Output is measured at 1250 eng RPM and 15V at the alternator.
Output varies +/- 3A due to temperature and 5A more measured at the alt rather than the batt.

Apparently any one of the 3 listed alternators is suitable for the wiring on the trucks as no mention is made of upgraded wiring needed for the larger alternators.

The best solution for the original poster would be to purchase the FSM, refer to the Service Diagnosis chart on pg 8-23 and follow the Service Procedures sections for the various components of the charging system.

If the wire is smoking, there is an over current fault that needs to be rectified. Either there is too much load connected to the circuit, a short circuit to ground or a bad regulator allowing the alternator to generate excessive voltage which increases current flow thru the circuit.
A bad body to engine ground will also overcharge a battery and possibly overheat the main alternator wire.

[martincom]

Let's help the fellow.

I did. You took issue with the recommendations. I gave you my reasons, and it drifted from there. I don't write these things just for this thread, but because people use search to learn about these trucks. Hopefully, the combined exchange will serve multiple people's purposes, whether they want a stock repair or an upgrade. The conversation served both purposes, no offence taken or intended.

Mark, the reference you cite conflict with each other. The Powerstream reference indicates 55 amps for #10 while the bluesea is a very conservative 30 amps. There maybe something about marine applications that would limit ampacity to a very conservative amount. I don't have any experience in marine applications to know. In my business, one of the things we did was service emergency vehicles and build them. So we dealt wit a LOT of electrical and electronic equipment. (My main business was two-way radio. We were a dealer and service center for Motorola.) We also built 911 dispatch centers. We utilized the NEC ( National Electric Code) as our reference for choosing and sizing conductors, which was mandatory in a structure. The code is pretty conservative with an emphasis on fire protection. An emphasis is placed on a conductor's ability to dissipate heat. While the code does not apply to automotive applications, we still utilized it as a guide. I've attached a couple of tables for your reference. One is for conductors in a cable or raceway and the other is for free air. In an automotive application, wiring is able to dissipate more heat because it is not in a raceway, conduit or heavy jacket. Likewise, when taped into a harness or in split loom, it can't dissipate as much as free air.

[Wildergarten]

Mark, the reference you cite conflict with each other. The Powerstream reference indicates 55 amps for #10 while the bluesea is a very conservative 30 amps.

It depends upon how one uses the Powertrain calculator to which I was referring. Into the respective fields, I entered: 10AWG, 12V, at 40A over 10 feet, representing the loop from the alternator to the ammeter and back. The calculator returned a drop of nearly a volt, and that's without the connector inline, or the subsequent feed to the end uses, which are also marginally undersized in my opinion.

Whether a wiring system delivers the voltage to run a device versus whether it will fail are two different things. My experience of these trucks is that when the voltage regulator calls for full current, the lights brighten, the wipers speed up, and you can hear the pitch of the blower rise. All of those indicate that the wiring voltage drops are excessive. My old Dart did it too, until I fixed it.

Of the four Sweptline trucks I've had, ALL FOUR came to me with the alternator-battery loop re-worked. A Google search of the string with the required terms: "1960s+dodge+wiring+alternator+melt" returned nearly a million hits. (https://www.google.com/search?hl=en&as_ ... type=&tbs=) A Google Image search "1960s+dodge=firewall+connector+melt" returned 870,000 (https://www.google.com/search?q=1960s+d ... CA0&uact=5). Go look at the pictures. It's a problem. Best to fix it.

I'd go with #8AWG THHN wire, heavy copper soldered on ring lugs, with heat shrink on the joints, and a pair of bulkhead studs. I bought the latter for $20 at Amazon (https://www.amazon.com/Cllena-Premium-J ... B078ZXYD1L). I'd also use internal tooth washers on the stud nuts. True, they are not ideal, as one of the studs has a hole through it as a wire clamp. But I have yet to find a pair in that size without it. I could simply replace the stud itself with a cut-off brass bolt or piece of stainless all-thread. Don't know. The Moroso 74144 Red Thru Panel Connector is 3/8, but it takes a lot of real estate on the firewall with some pretty big holes. One can also get boots to cover the stud and lug such as these: https://smile.amazon.com/Red-Black-Stud ... 4X9T&psc=1.

As you can tell, I really don't mind debate. Exercised politely and with mutual respect, it brings out the best in everybody... and everybody else benefits from the exercise.

Mark

[PwrWgnDrvr]

It depends upon how one uses the Powertrain calculator to which I was referring. Into the respective fields, I entered: 10AWG, 12V, at 40A over 10 feet, representing the loop from the alternator to the ammeter and back.

There is no such thing as a loop from the alternator to the ammeter and back.
That would be a dead short and burn up instantly.
The circuit (loop) is positive lug on alternator, to ammeter, to battery positive post. The other half of the circuit (loop) is negative battery post to ground on the engine block, thru the block and alternator mount into the alternator case which is connected to the coil.
Is there really 10' of wire from the the alternator to the battery?

Even if there is, P=EI, so 1v x 40A is a mere 40 watts of heat to be dissipated. That's nothing over 10'.

Just to be clear and accurate, electricity flows from negative to positive, so the "loop" description starting at the alternator thru the ammeter to battery is merely a wiring route, NOT a directional indicator of current flow.

[PwrWgnDrvr]

My experience of these trucks is that when the voltage regulator calls for full current, the lights brighten, the wipers speed up, and you can hear the pitch of the blower rise. All of those indicate that the wiring voltage drops are excessive.

This happens when the alternator RPM increases and is capable of providing the full voltage allowed by the regulator, It is absolutely normal and to be expected.
Regulators do not "call for full current", nor do they regulate current. The function of the regulator is to LIMIT the voltage produced by the alternator to a set maximum, which in turn limits the output to its design maximum. And in fact, the alternator output current does not even flow thru the regulator.

[PwrWgnDrvr]

Mark, we're not talking about the man's problem...(ad nauseam!)....and our bantering back and forth about design criteria is probably only confusing the issue. His problem has nothing to do with the capacity of the wiring or the connectors. Let's help the fellow.

[Wildergarten]

My experience of these trucks is that when the voltage regulator calls for full current, the lights brighten, the wipers speed up, and you can hear the pitch of the blower rise. All of those indicate that the wiring voltage drops are excessive.

This happens when the alternator RPM increases and is capable of providing the full voltage allowed by the regulator, It is absolutely normal and to be expected.

That's not at all what I'm talking about. This happens at cruising speeds.

[Wildergarten]

.

[Wildergarten]

There is no such thing as a loop from the alternator to the ammeter and back.

I'm talking about a wire loop, not a full circuit, effectively an open loop. It goes from the alternator, through the firewall to the ammeter, and then to the relay. The two wires go right past each other with current flowing in opposite directions, hence the application of the term.

Try reading it for what is intended rather than what you can make of it.

[Wildergarten]

On this thread, I've offered part numbers, vendors, specifications, and cited the cause of the problem with very good sources. You grab a digression and characterize it as ALL that was offered.