Not getting 12 volts to coil

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Dusten said:
So 9volts coming out of the ignition switch and 9v at the coil + is within normal limits?
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NO You are "darn near" clear up to 11v at the battery cranking. Two volts drop between the power into the switch and the coil is a fair amount of drop. You should be able to see where this is happening. Measure at the ign switch connector and try to probe both interior and engine bay side of bulkhead connector. "Wiggle test" the bulkhead connector and ignition switch connector see if that drop changes.
 
This a 50 yr old car. Who knows what electrical accessories have been added & connected to the ign cct. This might explain the 2v voltage drop.

The simplest thing you can do now to eliminate voltage drop as a problem is this:
disconnect all wires connected to the coil [+] terminal. Run a jumper direct from the coil [+] to battery [+] terminal. If the car starts & runs ok, then you have a voltage drop issue. One thing at a time, report back.
 
When cranking the current flows through the ign 2 circuit. Neither the ballast resister nor any conjectural additional loads on the ignition 1 (run) circuit would be relevant. I think you are taking him off track.
67Dart273 seems to be walking the OP through the diagnoses very well.
 
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Bewy said:
This a 50 yr old car. Who knows what electrical accessories have been added & connected to the ign cct. This might explain the 2v voltage drop.

The simplest thing you can do now to eliminate voltage drop as a problem is this:
disconnect all wires connected to the coil [+] terminal. Run a jumper direct from the coil [+] to battery [+] terminal. If the car starts & runs ok, then you have a voltage drop issue. One thing at a time, report back.
Click to expand...

THE ABOVE IS INCORRECT with an electronic ignition as doing the above WILL NOT PROVIDE POWER TO THE BOX
 
67Dart273 said:
WILL NOT PROVIDE POWER TO THE BOX
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True but Bewy did not say to remove power anywhere else. All that is being done is providing a positive battery voltage to the coil during start. Run voltage still might be low due to voltage drop, I would add a jumper from battery + to blue (power in to the box) as well. That way the box and coil are both fed directly from battery.
 
Well but if voltage drop is present on IGN1 as well, the drop will still be "there" to the box and may skew the results.
 
67Dart273 said:
Well but if voltage drop is present on IGN1 as well, the drop will still be "there" to the box and may skew the results
Click to expand...

But not with a second jumper.

Neither here nor there.

The jumpers are only a diagnostic tool to prove that a voltage drop is indeed an issue. Where it is or why is an intire other thing.
 
speaking of voltage drop, is a 1.7 drop on the positive path of the alternator while cranking excessive? An alternator said that drop was normal due to the starter..What's normal? I have a 70 'Cuda and could not get this kind of depth on an e-body site. I'm getting ready to check my ignition switch, as voltage is only 9 on the ballast resistor with current coming through the bulkhead connector on cranking, which shows up at the coil +.
 
I don't know what you mean. The alternator is pretty much not involved during cranking. The important thing is the drop between the battery and starter, so this means the battery posts (not the cable clamps, the actual posts) as the source, and the engine block and the starter hot stud as the load. Several ways to go about this

For electronic ignition, about 10.5 is minimal, although some will fire "lower." Most older cars in good condition that don't have "too hot" an engine will start much lower voltage if equipped with breaker points, maybe down in some cases to "barely turns over."

Modern PM starters have helped immensely as they don't draw nearly as much current.

9V right at the coil when cranking is pretty low. The bypass (Ign2, usually brown) circuit should be providing that voltage. The bypass circuit is hot same as the yellow "start" wire but is a separate set of ignition switch contacts.

Possibilities are harness drop from battery, fuse link, through the bulkhead terminals, through the ignition switch and it's connector
 
This simplified diagram is from the MAD electrical article on the ammeter/ bulkhead connector. It applies to "most" old Mopars

Catalog

amp-ga18.jpg


The path for coil current is not fully shown above. Ignoring electron flow, the "path" is battery---fuse link--through the bulkhead (BIG RED) to and through the ammeter, out on BLACK---to the WELDED SPLICE and branch off at the splice to the IGNITION SWITCH and from there out of the switch on the (brown?) IGN2---back out through the bulkhead connector and to the coil + side of the coil
 
I'll double check but pretty sure both the 1985 SJ Service manual and SUN
s VAT 40 manual consider starting voltage down to 9 or 9.5 Volts acceptable. Not great or even good, but OK. Also its very important to fully charge the battery before testing.
wrecks said:
speaking of voltage drop, is a 1.7 drop on the positive path of the alternator while cranking excessive? An alternator [shop?] said that drop was normal due to the starter..What's normal?
Click to expand...
Two different things can be called 'voltage drop'.
Based on your description*, it sounds like you are describing the drop in battery's output voltage when during start. This is due to the large draw from the solenoid and starter motor.
To determine this; Measure the the voltage across the battery terminals during start.

To find out if there is a "drop on the positive path"; take additional measurements at the same time at other locations along the current path.
> There should be no measureable difference between the battery positive terminal and the alternator output stud.
> During start, there may be a difference between battery positive and the alternator's blue field wire. It's normal and not important.**
> While running, there should be only a small voltage difference between the run circuiit and the bettery positive and the alternator output terminals.​

*description
wrecks said:
as voltage is only 9 on the ballast resistor with current coming through the bulkhead connector on cranking, which shows up at the coil +.
Click to expand...

**When the key is in start position, the switch only connects the feed in (J1) to the two circuits labeled Start and Starter.
upload_2021-4-15_8-51-3.png


With the key in Start position, any current flowing through the alternator field will have to go through the ballast resistor. That will naturally cause a voltage drop.
However since there are other easier paths to ground, hardly any current may flow through the resistor. In that case the voltage on both sides of the resistor will be the same.

Fully illustrated sequence of current flow for a Mopar starting sequence in this post. Bump Switch
 
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Looking for resistance in the system.
When the engine is running, the voltage at the battery positive and the alternator output and the Run Circuit (J2) should be very close.
If there is a difference between the battery and the alternator, check the ammeter to see how much current is flowing. The factory considered .7 Volt difference with a 20 amps flow the maximum acceptable.

upload_2021-4-15_9-10-51.png
 
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Update:
Disregard this...
answered wrong thread.
Sorry.
 
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Joey4speed said:
Apologies.
Answered wrong thread.
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I'm sorry I interrupted. I'll have to study what all has been said. I'm trying to avoid having to get at the cylinder switch in the steering wheel, as my '70 bulkhead connectors look clean, and the drop seems up inside my dash from the splice from the two ammeter clips. What you all have said will really help me out. Thanks. The 'Cuda site did not seem to have an searchable database like yours. I'm 72. motivated, but not a natural, so to speak.
 
You can easily access the connector of the ignition switch coming out of the column. That will tell you if it's in the switch, as you can access both halves of the connector (from the rear) and condemn or eliminate it. One wire will of course be the feed into the switch, and that comes from the welded splice. So if it's low there, it means it's back at either the ammeter or bulkhead connector

It can be difficult but not always impossible to access the passenger compartment side of the bulkhead connector. Consider removing the front seat. Some of us rig a "bench" outside the car to act as a "cot" to lay on up under the dash.

The bulkhead connector comes apart in sections. You would do well to pull it apart and inspect the terminals. The terminals all release and pull out of the connector. All you really need is some small needle nose and a quite small screwdriver

This thread has some good info on what to expect

Sources for Chrysler type wire terminals

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upload_2020-5-10_11-36-43-png.png
 
I have found 12.5 coming into the blukhead connector's red and black wires, which I think lead up to the 2 ammeter wires under the dash. And going under the steering wheel, I've found only 10.8 on at the steering wheel connector's red and black wires. This difference sound like what you said, the bulkhead connectors. One strange thing is that turning the ignition switch gets continuity for 2 clicks, but if I turn the switch 'till it stops, I lose continuity. I still don't understand why I get 9 volts at the battery stud on the alternator when starting and get 10.7 between the 2 battery terminals when starting. This difference is exactly the 'voltage drop' I found by connecting my positive volt terminal to the alterhnato batt stud and the negative lead on the positive post of the battery.
 
wrecks said:
I have found 12.5 coming into the blukhead connector's red and black wires, which I think lead up to the 2 ammeter
wires under the dash
Click to expand...
. The largest diameter red and black wires probably are the A1 (Battery) and R6 (alternator feed). The 70 Plymouth manual will show exactly which cavity in the bulkhead connector they go through if that is a question.

wrecks said:
And going under the steering wheel, I've found only 10.8 on at the steering wheel connector's red and black wires.
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On the steering column connector the heaviest red is the power feed from the main splice.
The heavy black is probably switched accessory feed. Need to check the book for your car to be more certain. It only gets power when the key is switched to run or accessory. It supplies power to the windshirld wiper switch, turn signals, and through 2 or 3 fuses in the fusebox the heater fan, radio, and maybe a few other options.

To find resistance in circuit using voltage drop, current must be flowing through the resistance.
I'm not clear on whether 10.8 V was between J1 and ground, or between J1 and Accessory (or whatever black it was ).
Also what was turned on, if anything.

upload_2021-4-15_8-51-3-png.png
 
1970 Barracuda column connectors
upload_2021-4-20_8-55-3.png


Connector diagram
upload_2021-4-20_9-1-38.png

Battery 1, J1-12R is a 12 ga red wire that connects to the main splice. It gets power from the battery or alternator, whichever has higher voltage.
Accessory, Q2-12BK is a 12 ga black wire that provides power to many of the 'accessories' that gets power when the key is on or in accessory.
Ignition, J2A-16DBL* is 16 gage dark blue wire with white stripe for running the essential engine electrical items.

Bulkhead connectors on engine compartment side.
upload_2021-4-20_9-50-58.png

Battery (A1) goes to cavity 16
Alternator output (R6) goes to cavity 18.

We can add those details to the schematic.
upload_2021-4-20_10-10-38.png


Now here's a couple of exampls of how to look for resistance.
(example 1) Engine Off, Key Off, Turn on parking lights:
About 4 amps of current flows from the battery to the lights and back to the battery. Path of current shown with orange arrows.
upload_2021-4-20_10-19-28.png


If there is resistance to the current between the battery positive and the main splice it will show up as a voltage drop.
upload_2021-4-20_10-24-49.png


Turning on the headlights will increase the current to roughly 12 amps. This will result in more voltage drop through the resistance.
upload_2021-4-20_10-30-45.png


.15 V drop for 15 amps isn't bad.

(example 2). Engine running, battery fully charged, turn on headlights.
step 1. Start engine and allow battery to recharge. Ammeter must be at zero. Measure voltage to ground from Alt output. It should be around 14 Volts.
step 2. Measure voltage difference between alt out and battery. Turn on headlights. Measuer voltage drop with lights on.
upload_2021-4-20_10-45-30.png

The voltage difference in this example indicates a fair amount of resistance in the the R6 line, probably at the connectors but could be damaged wiring.
 
Mattax said:
. The largest diameter red and black wires probably are the A1 (Battery) and R6 (alternator feed). The 70 Plymouth manual will show exactly which cavity in the bulkhead connector they go through if that is a question.


On the steering column connector the heaviest red is the power feed from the main splice.
The heavy black is probably switched accessory feed. Need to check the book for your car to be more certain. It only gets power when the key is switched to run or accessory. It supplies power to the windshirld wiper switch, turn signals, and through 2 or 3 fuses in the fusebox the heater fan, radio, and maybe a few other options.

To find resistance in circuit using voltage drop, current must be flowing through the resistance.
I'm not clear on whether 10.8 V was between J1 and ground, or between J1 and Accessory (or whatever black it was ).
Also what was turned on, if anything.

View attachment 1715725958
Click to expand...
 
I want to thank you for giving me all the pieces (& then some). I have a 1970 Factory manual, but I have not seen the steering column connector diagrams in mine. I got 12.5 volts coming into the car from the bulkhead connector with the battery hooked up and only 10.5 at the batt 1 and ignition 2 end of the column connector. I'll try to clean (replace) the connectors that relate to ignition 1 and 2 that would directly affect coil voltage. I'm trying to avoid having to replace the ingition switch, because of 2 Miller-type tools I don't have. You have helped me, because I don't have an automotive background and I see the voltage drop depends on how much current is flowing. All my drop tests were done with the starter going. I've had my car 20 + years and have not used it much. It's stock (warranty block by casting date on the block) in relation to build date and 'clean' serial number plate from what I can see. Years ago, I used to get advice from Karl Pippart III, but I lost contact when his magazine folded.
 
Ypou're going in the right direction. So far I don't see a need to replace anything. A little more testing will narrow down any resistance of concern.
wrecks said:
I have a 1970 Factory manual, but I have not seen the steering column connector diagrams in mine.
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That I can't help on. I know at least some years there were several printings of service manuals. The 1970 Plymouth Service Manual with the diagrams above is the digitized version I got from mymopar.com
wrecks said:
All my drop tests were done with the starter going.
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This is really important. You did write that in your opening post. My fault for not following up or being clear about this.
wrecks said:
I got 12.5 volts coming into the car from the bulkhead connector with the battery hooked up and only 10.5 at the batt 1 and ignition 2 end of the column connector.
Click to expand...
I ignored the apparent mislabling of the Ignition 1 and 2 on the connector drawing because my focus was on the checking for resistance between the main splice and the battery and alternator.
10.5 Volts at Batt 1 (Red) and (blue) on the column connector during start may be OK. Its OK assuming there is no current flowing through the ballast resistor.
10.5 Volts at Batt 1(Red) and the (brown) 14 ga wire during start is great. It shows there is no resistance through the start connections in the ignition switch.
Let's illustrate that:
All of the voltage measurements are to ground.
upload_2021-4-22_9-53-13.png


It's likely the battery voltage with the starter turning is also around 10.5 Volts. You'll have to measure that.
The starter solenoid and motor draw so much current that the battery voltage always drops somewhat.


upload_2021-4-22_10-16-39.png


If you suspect there is resistance at the bulkead connector, the battery and alternator connections can be tested using the examples in my earlier post.

Once you know those are OK, you can check for resistance between the alternator output and the ignition run circuit.
With the engine running, the voltage at the alternator output terminal (Batt) and the blue J2 wire should be the same.
upload_2021-4-22_10-27-24.png

If the choke is equipped with an electric assist, that could draw some additional current during warm up. Even so, the circuit's voltage should be very close to the supply voltage.
 
Mattax said:
Ypou're going in the right direction. So far I don't see a need to replace anything. A little more testing will narrow down any resistance of concern.

That I can't help on. I know at least some years there were several printings of service manuals. The 1970 Plymouth Service Manual with the diagrams above is the digitized version I got from mymopar.com

This is really important. You did write that in your opening post. My fault for not following up or being clear about this.

I ignored the apparent mislabling of the Ignition 1 and 2 on the connector drawing because my focus was on the checking for resistance between the main splice and the battery and alternator.
10.5 Volts at Batt 1 (Red) and (blue) on the column connector during start may be OK. Its OK assuming there is no current flowing through the ballast resistor.
10.5 Volts at Batt 1(Red) and the (brown) 14 ga wire during start is great. It shows there is no resistance through the start connections in the ignition switch.
Let's illustrate that:
All of the voltage measurements are to ground.
View attachment 1715726989

It's likely the battery voltage with the starter turning is also around 10.5 Volts. You'll have to measure that.
The starter solenoid and motor draw so much current that the battery voltage always drops somewhat.


View attachment 1715727008

If you suspect there is resistance at the bulkead connector, the battery and alternator connections can be tested using the examples in my earlier post.

Once you know those are OK, you can check for resistance between the alternator output and the ignition run circuit.
With the engine running, the voltage at the alternator output terminal (Batt) and the blue J2 wire should be the same.
View attachment 1715727015
If the choke is equipped with an electric assist, that could draw some additional current during warm up. Even so, the circuit's voltage should be very close to the supply voltage.
Click to expand...
 
My voltage readings by removing the plastic housings in front of the bulkhead connector (12.5), and under the dash from an uncoupled harness connector that had the ingition switch (10.5) were with the battery hooked up, but nothing running except the lights inside the car. I don't know how to test the ignition switch directly, because it seems to activate the switch, I would have to have the proper harness connector hooked up. If I had 10.5 while cranking, I'd be home free. To test directly at the appropriate location in a circuit, do I insert a needle into the wire ?
 
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