Hello all, so I have some electrical issues going on in my 1974 duster I bought. It was running the other day then just stalled. The ignition lost power and the headlights wouldn’t come on. I tested the batt which is a couple days old I just bought and it’s fine. I inspected the red wire from the starter relay going into the fire wall that has a fuse which was blown. I replaced the fuse everything worked until I started it again. I traced it through the fire wall and as far as I could and I’m pretty sure it goes to the ammeter. Now I read how to delete the ammeter but I’m confused on some parts. First is run a 10 gauge wire with a fusable link from the alternator output to the positive stud on the stater relay. Then do you disconnect the wire that was going from the alt output ? If so what do you do with it and can someone please explain simple terms to delete the ammeter and still have power to the headlights and ignition?
74 duster elelctrial help
- Thread starter nick0705
- Start date
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You need to send me a PM, that is, "conversation." I have a digi copy of the 74 manual which is unique, as the electrical has CHANGED from 73. There is no free download of a 74 manual
You mail me a prepaid mailer with a thumb drive, and a return addressed/ paid return mailer, and I'll copy the files and send it back
There should be no fuse in the RED ammeter wire. If so, the fuse link has blown at some point, and someone has replaced it with a fuse, which is likely not heavy enough under some charging conditions, AKA heavy load and battery that is partly discharged
As far as the ammeter bypass, it's not quite that simple BECAUSE the existing wiring STILL must be in decent shape as it stil acts to supply power, through the bulkhead, into the passenger compartment. You must make certain that the bulkhead terminals for the big RED ammeter wire, the big BLACK alternator output wire are in good shape, and that either the ammeter terminals are in good shape, or that you splice the red and black ammeter wires together
You want to use a good big wire for the bypass with either a fuse / fuse link or breaker. This depends on the size of wire and the size of the alternator.
You mail me a prepaid mailer with a thumb drive, and a return addressed/ paid return mailer, and I'll copy the files and send it back
There should be no fuse in the RED ammeter wire. If so, the fuse link has blown at some point, and someone has replaced it with a fuse, which is likely not heavy enough under some charging conditions, AKA heavy load and battery that is partly discharged
As far as the ammeter bypass, it's not quite that simple BECAUSE the existing wiring STILL must be in decent shape as it stil acts to supply power, through the bulkhead, into the passenger compartment. You must make certain that the bulkhead terminals for the big RED ammeter wire, the big BLACK alternator output wire are in good shape, and that either the ammeter terminals are in good shape, or that you splice the red and black ammeter wires together
You want to use a good big wire for the bypass with either a fuse / fuse link or breaker. This depends on the size of wire and the size of the alternator.
1974 was a bad year for that. I pulled my hair out on this 74 that sat here for years, It was the bulk head . Yes that is a 74.
Mattax
Just the facts, ma'am
Just say NO.
This is exactly why that 'advice' is poison.
When the fusible link blows there is a dead short in the system, or it has been horribly abused over time.
What I mean by dead short is the battery positive is connecting to ground.
You must find the problem(s)
The ammeter is nothing but a flat plate with two studs pressed in. If the studs are loose there will be resistance or no connection, otherwise its fine. The needle deflect due to the lightl electromagnetic field created when electrons move through the plate. Don't waste your time chasing a red herring. If the ammeter connections were shorting, the fuse or fusible link would blow as soon the battery was connected.
Here's how it works.
The battery feeds goes to a junction on the other side of the ammeter.
All of the wires connected at that junction are hot when the battery is connected.
Short any of those wires and the battery will max discharge. It will be big spark show. The fusible link will melt more quickly the worse the short. It's a better than no protection but not a guarentee.
Also notice the ignition feeds are not fuse protected. If there is a short in the ignition feed, the engine stops running. That stops hte alternator but the battery is still connected. The ammeter will show severe discharge from the battery until you turn the key switch to off, or something burns through. The fusible link is 16 gage but so is ignition wire. Which one will melt first is anyones guess. The link protects the 12 gage wires and maybe the 14 gage wires, but not the 16 a and 18 gage wires.
You can find the problem by looking for signs of where wires are burned, and looking for places insulation is missing and wires are rubbing against metal or getting pinched.
Anotehr way is to use a lamp or a circuit breaker and test each circuit. Or disconnect the battery and use a multimeter or circuit tester.
Post some pictures and we can probably come up with a plan to find the problem.
Mattax
Just the facts, ma'am
And if your Duster has the heated back glass defrost, its wired a little differently. So we need to know that. Also if there are any modifications or add-ons to the electrical system.,
Yes '74 is a bit more challenging than '72 and earlier but nothing you can't solve.
Here's how the standard system is supposed to work.
When the engine is running and the battery is charged, electron flow is shown by the orange arrows. The alternator supplies power around 14.3 Volts.
The ammeter shows zero because the battery is not supplying power, nor is it getting recharged. Step on the brakes or turn the lights on and the ammeter stays at zero. Power is coming from the alternator.
The ammeter is calibrated aprroximately 40 amps discharge to 40 amps discharge.
Anything over 20 amps is high current, and 40 is a major problem. The correct ammeter reading depends on circumstances. For example, if the ammeter reads discharge while the engine is running, for some reason the alternator is not supplying power. If it is showing charge after starting, that's because the battery needs recharging. That's normal and not a problem.
Yes '74 is a bit more challenging than '72 and earlier but nothing you can't solve.
Here's how the standard system is supposed to work.
When the engine is running and the battery is charged, electron flow is shown by the orange arrows. The alternator supplies power around 14.3 Volts.
The ammeter shows zero because the battery is not supplying power, nor is it getting recharged. Step on the brakes or turn the lights on and the ammeter stays at zero. Power is coming from the alternator.
The ammeter is calibrated aprroximately 40 amps discharge to 40 amps discharge.
Anything over 20 amps is high current, and 40 is a major problem. The correct ammeter reading depends on circumstances. For example, if the ammeter reads discharge while the engine is running, for some reason the alternator is not supplying power. If it is showing charge after starting, that's because the battery needs recharging. That's normal and not a problem.
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thank you I know the whole issue is why is that 30amp fuse blowing after running for a min and kills ignition and headlights. So I sent these pics the alt wire is through a loom then I can see a connection then back in a loom. On the other side you have the red wire with a 30amp fuse from the stater rely through drilled wholes in the firewall there is also another wire going through firewall not sure if it’s a splice off the alt or not. So what i want to do is keep the alt gauge hooked up and run a 10guage wire withe a 14guage fuseable link from alt to stater relay and remove that 30 amp fuse and put a 16 gauge fuseable link in. So if doing so the circuit would remain factory we’ll kinda and alls I’m doing is adding the alt to batt post wire to stater relay sorry im just lost the connections everywhere look find idk why all of a sudden it started doing this last week it was running but after it got hot it would stall and have a hard time restarting and staying running so i know thats prob a diff issue but im more worried about electrical currently.
There never was a fuse, originally, instead the OEM fuse link, which is a poor deal
The wiring, the bulkhead feed through terminals and the ammeter itself are all actually too light for anything over about 40-45.
"Ma" made an attempt to improve that circuit with optional 65A alternators using what is kinda known as "fleet/police/taxi" wiring. This is documented in some service manuals. They actually ran two heavier wires through separate gromments in the firewall
A 30A fuse would not work for long, even with the original 37A alternator during heavy use.
The wiring, the bulkhead feed through terminals and the ammeter itself are all actually too light for anything over about 40-45.
"Ma" made an attempt to improve that circuit with optional 65A alternators using what is kinda known as "fleet/police/taxi" wiring. This is documented in some service manuals. They actually ran two heavier wires through separate gromments in the firewall
A 30A fuse would not work for long, even with the original 37A alternator during heavy use.
Mattax
Just the facts, ma'am
I'm going to guess you are using a phone rather than a computer or tablet. If you can make the photos twice the size, that will help.
Lets start with this question. The protection is based on the weakest item in the system or the weakest wire that we don't want to have burn if there is a short or overload.
It doesn't matter what the alternator can produce.
Nor does it matter how big the battery is. Even the smallest battery capable of starting your car's engine is capable of supplying a couple of hundred amps!
However, if the car has a 60 amp factory alternator, then the car was originally equiped with a bigger battery and a heavy duty wiring. I think your photos show some of that.
You think he has the fleet wiring? I cannot tell.
But the thing is, no10 can stand WAY more than a 30A fuse for short times.
My favorite is when I built the drive electronics for the wheelchairs. The power/ fuse box from the battery is a pair of no10 in each leg, IE 2x no 10 for the positive side, and 2X no 10 for the negative side. Each motor is supplied with a no. 10 in each leg.
I believe the breakers we used then were 2X 75A quite slow blow, one in each no10 leg
When testing modules in the test chair, I'd roll it up against the building or a curb, first ahead, then reverse, and firewall the joystick. This was a default 'full power' program for testing. The entire module and motors would draw OVER TWO HUNDRED AMPS and you'd sit there for 10--15 seconds that way.
You simply cannot operate a Mopar ammeter circuit with a 30A fuse, regardless of how bad you'd like to protect it. It is what you are stuck with, unless you want to rework the entire circuit.............or just do a bypass.
But the thing is, no10 can stand WAY more than a 30A fuse for short times.
My favorite is when I built the drive electronics for the wheelchairs. The power/ fuse box from the battery is a pair of no10 in each leg, IE 2x no 10 for the positive side, and 2X no 10 for the negative side. Each motor is supplied with a no. 10 in each leg.
I believe the breakers we used then were 2X 75A quite slow blow, one in each no10 leg
When testing modules in the test chair, I'd roll it up against the building or a curb, first ahead, then reverse, and firewall the joystick. This was a default 'full power' program for testing. The entire module and motors would draw OVER TWO HUNDRED AMPS and you'd sit there for 10--15 seconds that way.
You simply cannot operate a Mopar ammeter circuit with a 30A fuse, regardless of how bad you'd like to protect it. It is what you are stuck with, unless you want to rework the entire circuit.............or just do a bypass.
Some "former stuff" The white and blue is one side of the motor wires. Those busses had to be soldered into the board with a TWO HUNDRED AND FIFTY WATT american beauty old school iron with about a 5/16 dia chisel tip.
The other photo, with the red and black are the opposite side of the board, with one of the power in busses. The second from bottom photo shows all 4 power wires, the orange and red positive, and the grey and black negatives. At 200A and nominal 24V that is approx. 5KW for a short time.
EACH NO.10 CONDUCTOR is carrying nominal ONE HUNDRED AMPS
There are 24 mosfets, partly visible on the side of the enclosure/ heat sink, 12 for each motor. They carry about 20A each at full firewalled power
The bottom photo, soldering the no 10's into big Anderson connectors, I've forgotten the amp rating on them. 120? Not certain. As an irony, we had a battery powered fork lift which used 350-400A Anderson connector on the charging cord.
The other photo, with the red and black are the opposite side of the board, with one of the power in busses. The second from bottom photo shows all 4 power wires, the orange and red positive, and the grey and black negatives. At 200A and nominal 24V that is approx. 5KW for a short time.
EACH NO.10 CONDUCTOR is carrying nominal ONE HUNDRED AMPS
There are 24 mosfets, partly visible on the side of the enclosure/ heat sink, 12 for each motor. They carry about 20A each at full firewalled power
The bottom photo, soldering the no 10's into big Anderson connectors, I've forgotten the amp rating on them. 120? Not certain. As an irony, we had a battery powered fork lift which used 350-400A Anderson connector on the charging cord.
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Mattax
Just the facts, ma'am
Site went down for me so delayed response.
@67Dart273 I can't tell what that photo is showing even after blowing it up. Third one down. It shows a big grommet, but it could be for somehting else like A/C. Description wasn't clear.
This shows no damage that we can see. (No melting or charring)
In real life if there is corrossion on any of the terminals, then clean it.
It looks like some oxidation on the headlight switch terminals. The phto is too grainy for me to know for sure.
The battery is disconnected, Yes? Do that before touching the ammeter terminals.
If you remove those nuts, be careful not lose the insulating washers. If you want to leave it alone for now, that's fine too unless its corroded.
Next -
Are you telling us that in this photo there are two wires going through the sheetmetal just above the bulkhead connector? That would not be factory and could easily short unless they have grommets and the wires are supported so they don't get yanked or vibrate.
The big grommet is factory.
Grommets like this were used a variety of wires depending on the year and the options on the car. If the alternator or battery feed goes through that grommet, then the car came with a heavy wiring option.
Finally in this photo we see a connector by the firewall:
In the circle is the "engine connector". The alternator wire had its own connector.
I'm leaning toward a previous owner did a bunch of modifications unless that is the alternator wire going through the big grommet.
@67Dart273 I can't tell what that photo is showing even after blowing it up. Third one down. It shows a big grommet, but it could be for somehting else like A/C. Description wasn't clear.
This shows no damage that we can see. (No melting or charring)
In real life if there is corrossion on any of the terminals, then clean it.
It looks like some oxidation on the headlight switch terminals. The phto is too grainy for me to know for sure.
The battery is disconnected, Yes? Do that before touching the ammeter terminals.
If you remove those nuts, be careful not lose the insulating washers. If you want to leave it alone for now, that's fine too unless its corroded.
Next -
Are you telling us that in this photo there are two wires going through the sheetmetal just above the bulkhead connector? That would not be factory and could easily short unless they have grommets and the wires are supported so they don't get yanked or vibrate.
The big grommet is factory.
Grommets like this were used a variety of wires depending on the year and the options on the car. If the alternator or battery feed goes through that grommet, then the car came with a heavy wiring option.
Finally in this photo we see a connector by the firewall:
In the circle is the "engine connector". The alternator wire had its own connector.
I'm leaning toward a previous owner did a bunch of modifications unless that is the alternator wire going through the big grommet.
Thanks for all the feedback. Sorry about the photos yes I was using my phone I will try and take bigger ones. Yes those two wires are running through the firewall through drilled holes that the previous owner did I’m assuming. Next the alt main wire is running in a loom all the way across the back firewall so the 2 wires that are separate and running through the fire wall I would assume one is the alt wire. The red wire running though is the 30amp fuse wire I have traced that to the back of ammeter. So I guess I will have to open some of the electrical tape wires up and that loom to see if that black wire is the alt. So where I’m confused is the diagram you posted up there shows the red wire from the stater relay with a fuseable link going though the circuit to the left side of the gauge if you are looking at it head on. The photo I posted of my ammeter gauge the red wire is on the inner post is that correct? I really want to bypass this ammeter so I already know about the alt to stater relay the question is how do I do the ammeter side. Should I remove that 30amp fuse and put a 16 guage fuseable link in where that 30amp inline fuse is ? I will get more pictures for you guys. I will also trace that alt wire down to make sure it’s that other black single wire going though the firewall next to the red wire.
Mattax
Just the facts, ma'am
Yes see if you can trace where they go or come from. In my opinion those are short circuits waiting to happen.
The heavy alternator wire looks factory and yes it runs along th einside of the valve covers and then across the back of the engine bay all wrppped into a harness. Its probably 12 gage. If its 12 ga its the standard alternator output wire and should go to the bulkhead multiconnector postion P.
If it had the 60 or 65 amp alternator wiring, or came with a rear defrost grid, then there should be 8 gage wire and goes to a grommet like the one you pictured.
When reading the factory diagrams.
R is for alteRnator wires
A is code for bAttery wire
J is code for Ignition. J1 feeds the key switch, so its more than just ignition.
L is for lights
H is for Horn
S is for Start and since yours is a '74, the seatbelt interlock made the start circuits more complicated.
See no reason to open it up if its original wrap. Other harnesses we see a previous owner used split wire loom. So those you can peek in if you want.
The black wire to the ammeter is coded as an alternator output wire probably because the way the harness evolved from 1960. It also makes it very clear which wire to connect to which ammeter terminal.
The diagram I posted is a schematic. The purpose of a schematic is to show how the circuits work. The bundling, routing and hookups go in all sorts of directions to protect the wires and make the connections without strain.
On the instrument panel the red wire with ring terminal connects to the ammeter post with the R next to it. The black one with ring terminal goes on the other post. Always.
I won't help on that. Like I wrote above. That advice is poison. Nothing to do with the problem(s), and if anything is going to make it more difficult to solve.
Returning it to factory may solve the problem. Eventually you should do so.
I can't say just do it because something happened that caused a previous owner to put a fuse in. Most likely the fusible link failed. Was this due to a short? or overloading the circuit with modifications/add ons? or charging a dead battery by running the car? We can only make some guesses.
The connections on the ammeter don't look burnt or melted. That's tells us that if there was an overload, it was brief and the fusebale link failed quick.
The fact the 30 amp fuse is blowing suggests either a short, or your new battery is very low on charge.
Observe the ammeter after starting and if the needle swings above 20 amps charge, then the battery is low and/or the votlage regulation may be full fielding.
If the needle swings to past 20 amps discharge, then there is a short.
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Mattax
Just the facts, ma'am
We can use the schematic to understand how the circutis work and what to expect.
For example. What wires and circuits are hot with the key off?
What happens if we open the door and step on the brake pedal leaving the door open?
And here's how the circuits work with the engine running and the battery recharging.
Knowing what the ammeter indicated before the fuse blew would help us figure out what is causing the line to have more than 30 amps go through it.
For example. What wires and circuits are hot with the key off?
What happens if we open the door and step on the brake pedal leaving the door open?
And here's how the circuits work with the engine running and the battery recharging.
Knowing what the ammeter indicated before the fuse blew would help us figure out what is causing the line to have more than 30 amps go through it.
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Mattax
Just the facts, ma'am
PS. if you don't want to go to a fusible link, some people have used slow acting 'maxifuses'. Some folks on the 'mini-mopar" forum made some comparisons with fusible link applications to the same circuits in later model that used maxifuses.
Thanks you so much for helping. I tried to pm you I was going to just give you my phone number so I can send better pics and talk to you and explain everything. I prefer to keep the ammeter hooked up and just fix and figure out why that fuse is blowing. I do want to run the 10 gauge wire with a 14guage fuseable link from alt output to the stater relay once all this is figured out
Also, it might be a charging issue as well. I just haven’t had it running long enough to check. I just replaced the batt about 2 weeks ago so it might be low even though it shows 12.3 volts with the voltmeter. The batt was replaced bc the car was sitting for a couple years. I took it to get check and it came back bad at autozone. But I could have a charging problem. The first time it shut off and blew that fuse I noticed some minor smoke which looked like it came from the starter area I check the starter wires and everything looks fine. Doesn’t mean it’s good either but it cranks and will start if I replace that 30amp fuse but runs for maybe 30 seconds and shuts off and I lose all power to headlights ignition. So there cleary is a short. I will work on it today and get some better pictures.
Mattax
Just the facts, ma'am
I consider 12.3 Volts a bit low. Brand new and fully charged should be 12.6 to 12.8
Put it on a slow charger if you can.
better way to check condition is with a load tester or acid tester but volmeter does give us a ballpark we can work with.
My PMs are full because I was gold membership and haven't renewed due to the PIA of dealing with paypal. It's in my will be getting 'round to it' file.
Put it on a slow charger if you can.
better way to check condition is with a load tester or acid tester but volmeter does give us a ballpark we can work with.
My PMs are full because I was gold membership and haven't renewed due to the PIA of dealing with paypal. It's in my will be getting 'round to it' file.
Okay so I traced these 2 wires going into the firewall. This is what I found. The red wire from starter relay through that 30amp inline fuse goes through the harness in the dash to the ammeter plus side on the gauge. The other wire is the alt feed wire it’s green going though the wall and as you can see in the second picture with the butt connector the wire came out when I pulled the electrical tape off. The last pic is the welded splice. Other than that connector I don’t see any other issues in the ammeter circuit other than that 30amp fuse being too small. So what’s the best approach here . Should I delete the guage ? Put a volt gauge in ? Leave the origanal way with the ammeter and just fix all the wiring and run the 10 guage wire with the 14guage fuseable link from alt feed to stater relay positive.
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Mattax
Just the facts, ma'am
Classic example of how people working on electrical system make problems with poorly executed work.
I still don't know what the story is with the big grommet, whether the A1 and R6 wire go to the multiconnector or through the grommet, or what those two wires are that go thrpough small holes drilled in the firewall.
When a car got the heavy wiring, often the standard wires were left in place or cut and capped. I'm still leaning toward a hack job modification or repair rather than a factory heavy duty setup.
If the alternator feed was that loose, then unlikely it was overcharging that caused the fuse to blow. Again the ammeter would have pointed to the cause.
I've already given you my suggestions. Apparently you want different answers.
I still don't know what the story is with the big grommet, whether the A1 and R6 wire go to the multiconnector or through the grommet, or what those two wires are that go thrpough small holes drilled in the firewall.
When a car got the heavy wiring, often the standard wires were left in place or cut and capped. I'm still leaning toward a hack job modification or repair rather than a factory heavy duty setup.
If the alternator feed was that loose, then unlikely it was overcharging that caused the fuse to blow. Again the ammeter would have pointed to the cause.
I've already given you my suggestions. Apparently you want different answers.
Thank you for being patient and I’d like to know where the ammeter was too but like I said it dies so fast I didn’t catch it. So I understand what your asking I’m trying to fix this. It looks like they did a hack job to me. They spliced into the origanal ammeter circuit it looks like and ran those two wires straight through the wall. I will fix that broken wire clean the ammeter posts real fix the spliced welded wires and put the dash back together. Once’s that’s done I will install a new 30amp fuse change the battery and go for a start and record the ammeter to see what it’s doing. And we can go from there sorry again I really am listening but I wanted to know where those 2 wires someone ran went all too bc I know and you know if you just do what’s shown in those pictures it leads to problems lol.
Mattax
Just the facts, ma'am
There really is no ammeter circuit. That line is the battery feed and charge. The ammeter is placed in the circuit as a way to monitor it.
The welded splice is the junction for two power sources (battery and alternator) to the wires feeding the ignition switch, the fuse box hot buss, the headlights, and for '74 the starter interlock. Some years the horn is there too but in '74 it was put on fused circuit.
So somebody needed to add two wires?
I think its good to clean everything up, but instead of testing live, maybe first just use an ohmeter or circuit tester. One thing is to check for shorts to ground in the unfused circuits and in the main circuits. Another thing to use the meter for is to help determine what those two wires connect to without taking everything apart.
There are several threads about making good electrical junctions and cleaning connections.
From the photos I think I would begin with a fiberbrush to phyically remove whatever can be accessed. Then something strong if needed. I trust De-oxit not to damage most plastics but be effective on copper oxidation. It comes in several strengths. But you'll see there are other things people use.
The welded splice is the junction for two power sources (battery and alternator) to the wires feeding the ignition switch, the fuse box hot buss, the headlights, and for '74 the starter interlock. Some years the horn is there too but in '74 it was put on fused circuit.
So somebody needed to add two wires?
I think its good to clean everything up, but instead of testing live, maybe first just use an ohmeter or circuit tester. One thing is to check for shorts to ground in the unfused circuits and in the main circuits. Another thing to use the meter for is to help determine what those two wires connect to without taking everything apart.
There are several threads about making good electrical junctions and cleaning connections.
From the photos I think I would begin with a fiberbrush to phyically remove whatever can be accessed. Then something strong if needed. I trust De-oxit not to damage most plastics but be effective on copper oxidation. It comes in several strengths. But you'll see there are other things people use.
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Mattax
Just the facts, ma'am
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Thank you, all that helps. Yes I don’t know why someone ran two new wires. I pealed it all back just to see what’s going on now I’m glad I did so I could see that wire that came out the connector. I will do as you suggest and go from there. Here’s a better picture of the splice. Thanks again. I’ll do all this clean up reconnect and secure wiring.
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