Testing circuits

[Righty]

Hi following on from my questions about the wiring on my ballast resistor, I realise that I’m going to get nowhere until:
A. I teach myself the basic layout of the circuits that start, run and charge.
B. Get a multimeter and test the various parts of those circuits.

So starting with the basics my first tests are:
1- check the battery voltage at rest. Should be above 12.6V?

2-check the voltage of the battery when the car is running and see if the voltage rises and increases with more gas, i.e. the alternator is delivering current too the battery. Should be 14V +/-?

3-positive probe to the output of the alternator ( thick black wire) negative probe to ground Should be 14V+?

There isn’t a stud on the alternator the connection is covered. Would it be safe to test the alternator by removing the output wire and taking the positive reading from the tab with the negative probe to ground?

I know this is all basic stuff but it’s the only way I’m going to learn. All the helpful folks who chipped in on my ballast resistor post I’d definitely welcome your continued patience

I have attached 3 photos, just to ask if I am reading the wiring correctly, a bit confused about the short wire spliced off the thick black wire back into the alternator.

Photo 1. the thicker black wire (output?) attaches at the bottom rear of the alternator.
The green wire (field?) attaches at right rear.

Photo 2. Output wire - black? and field wire - green?

Photo 3. Small black wire spliced to connector and attaches to alternator.

 

[Dana67Dart]

Let's start at the beginning.

1. What year car
2. What model car
3. Has the charging system been modified, if so what was done
4. Do you have a wiring diagram

There isn’t a stud on the alternator the connection is covered.

There is a cover but it is open on the back side, the nut that bolts it on is there.

Would it be safe to test the alternator by removing the output wire and taking the positive reading from the tab with the negative probe to ground

It is not a good idea to run an alternator without the battery attached.

a bit confused about the short wire spliced off the thick black wire back into the alternator

The small black wire goes from the output stud to a capacitor ( radio noise suppressor) that is attached to the alt.

Photo 1. the thicker black wire (output?) attaches at the bottom rear of the alternator.
The green wire (field?) attaches at right rear.

Thick black is output.
Green is a field wire. Depending on the alternator there could be a blue one too.

 

[67Dart273]

Not trying to make fun, not at all. Making voltage tests when you don't really know what it might should be, or what it is that you are actually showing, may not tell you anything, and can sometimes even lead you astray

Let's walk back to a say, 69 ish car with original breaker points. The ballast gets power from the key in "run" goes through the ballast, through the coil, down to the points, which are sometimes open, sometimes closed.

VOLTAGE DROP is sometimes good, sometimes bad, depending. The ballast, WHEN DRAWING CURRENT, is going to cause voltage drop to the coil.

When the points are open, there IS NO current flow, so there is no drop

This means that if you put your meter on ground, the key in run, and check both ballast terminals, both coil terminals. ALL OF THEM WILL show "the same as battery."

What have you measured, and what have you proved. If the points are open, There is no load, so if there is a problem, such as a bad connection in that circuit, it will not show up because there is no current, and even a bad connection may be good enough to make your meter read high.

Now again, with the engine bumped so the points are closed. Now, the key side of the ballast should be "same as battery." The coil side of the ballast, and the coil + should be the same, and should be (varies) 6-8 or maybe 10v. This is cause by the current through the circuit, and the ballast has resistance.

If you measure at the coil NEG to ground, the voltage should be very very low, perhaps 1/2 volt. This is measured across the points, and the worse they are (burned, worn) the higher that reading will be.

The point again, is you have to figure out what you should expect. I have some trouble on here. I'll detail some measurements, and sometimes guys will take a bunch, but NOT under the conditions specified. I'm not there, I cannot see what "you all" are doing, so I don't know how or what you have changed.


Not trying to discourage you, at all.

 

[67Dart273]

If you measure the alternator output stud, the thick black wire is the output through the bulkhead, through the ammeter circuit, back out the bulkhead and to the battery.

If you measure that without the thing charging, it shows really, nothing. There is no current there, with the engine stopped, and, once again, (that of course is a high current circuit) there IS NO current flow "static." So you will measure "same as battery" voltage. it may actually have a very poor connection, and may fail when charging.

Let's say there IS a very poor connection, perhaps where the black charge/ output wire enters the bulkhead connector. With the engine running fast idle, you may scare yourself when you read the alternator stud. IT MAY BE OVER TWENTY VOLTS, and still reading down fairly low at the battery, perhaps BELOW the target nominal 14V running voltage.

That's because our imaginary bad connection is losing that power/ voltage, and the regulator is thinking the battery is still low--so it ramps up the alternator output, trying to charge the battery. And there is a poor load continuity in that wire, so the alternator output goes up with low load.

Considering the (imaginary) problem we "have" that high voltage should be a clue, and could be considered a "normal" reading with that trouble existing. In other words the high voltage does NOT mean there is either anything wrong with the alternator OR the regulator.

On the OTHER hand, if the BATTERY is seeing this very high voltage, now this high reading means there IS some sort of alternator/ regulator problem

 

[Righty]

A very good place to start….
Ok so it’s a 69 Barracuda, and yep it looks like there’s been a few alterations to the electrical system. I have a copy of the relevant wiring diagrams from MyMopar but part of this process will also be trying to reverse engineer what the previous owner has done over time. My goal initially was to start with testing the basics in order to get a baseline to work from.

Alterations I can list so far:

5 pin OEM ECM ignition module.
4 pin ballast resistor with mystery additional connection on ignition end.
Original 2 pin ballast resistor still in place with one end still wired (don’t know if connected to anything).
Accelerate coil, however it doesn’t appear to have the accompanying ballast resistor fitted.
Non original alternator according to previous owner.
Electric fan circuit (capped off).
Aftermarket tachometer wired to coil.

What I’m hoping to do is unravel all the electrical tape and trace as much of the wiring as I can to create my own diagram and to understand what changes have been made.

 

[Dana67Dart]

5 pin OEM ECM ignition module.

Does it really have 5 pins? is the ECU an OEM Mopar part?



Real 5 Pin OEM Mopar ECUs will have marking on the transistor


4 pin on left - 5 pin on right

Aftermarket ECUs may have 5 pins but only use 4 internally and typically will have fake transistors with no markings

4 pin ballast resistor with mystery additional connection on ignition end.

4 pin ballast would be used with a TRUE 5 Pin ECU one left to right pair was for the coil and the other left to right pair was for the true 5 Pin ECUs power feed (not needed with a newer style 4 Pin ECU) As for the mistory wire on the ignition end what collor is it? does it look factory?

https://www.allpar.com/threads/how-...n-vehicles-that-originally-had-points.229005/

Original 2 pin ballast resistor still in place with one end still wired (don’t know if connected to anything).

Left over from when the car had a points dist. One end still wired... what color and does it look OEM?

Accelerate coil, however it doesn’t appear to have the accompanying ballast resistor fitted.

meaning it is not wired to A ballast resister or it is not wired to an Accel Ballast resister

Non original alternator according to previous owner.

It looks like a pre 70s round back alternator which would be proper for a 69

Electric fan circuit (capped off).

Does this mean it had an electric fan at one time but does not any longer?

Aftermarket tachometer wired to coil.

Usually not an issue unless it gets grounded out for some reason or you have an MSD box

What I’m hoping to do is unravel all the electrical tape and trace as much of the wiring as I can to create my own diagram and to understand what changes have been made.

classiccarwiring.com has great full color diagrams very reasonably priced best 25.00 I have ever spent

 

[jos51700]

If the battery is hitting ~14.5V when the car is running (it shouldn't go much over that when revving), I've yet to find a need to test the alternator.
Batteries are nominally 12.6-13.2 volts when fresh, hot, and not connected to the car. Connecting to the (old, not EFI) car and seeing a drop in battery voltage indicates that there's a Key-off draw.
Use your multimeter and watch the voltage on the battery when cranking. If it drops down to like 2-4 volts when cranking, it's got a shorted cell. It'll hold almost full voltage just sitting there, but won't hold a charge when you hit it with a load.

As far as starting circuits, I still don't understand 'em on SSEI Mopars, so I'm in on this!

 

[Mattax]

Non original alternator according to previous owner.

Well it is at least somewhat original as it has the OEM bearing. Maybe not from your car.

Does it really have 5 pins? is the ECU an OEM Mopar part?

Yes its wired for a Chrysler ECU with the 5 ohm resistor. See his otehr thread.

Left over from when the car had a points dist. One end still wired... what color and does it look OEM?

See his other thread.

Does this mean it had an electric fan at one time but does not any longer?

Correct

It looks like a pre 70s round back alternator which would be proper for a 69

But I can't see if its a grounded field or not.

classiccarwiring.com has great full color diagrams very reasonably priced best 25.00 I have ever spent

I think its a waste. He has the factory diagrams, he can use the color pdfs of those diagrams, and what is really needed is to redraw the diagrams filling in the modifications.

@Righty Its fine to learn about circuit testing, but befoer you actually do circuit tests, we need to know a bit moer about the circuits. Between the insulation colors, the wire sizes, and a continutity or resistance setting on a multimeter, you can figure this out. Its not hacked up that badly.

 

[Righty]

So it wired as per a 5 pin ECM with the power supply coming off the 5ohm side to pin 3. The additional wire is red with a white stripe, pretty sure it’s not OEM.

OEM ballast resistor blue and brown into single connector at one end. The wire from the other end now feeds the 4 pin resistor. Sorry Mattax was helping me with the wire numbers but I would need to look that up, we were working through some diagrams.

The coil is wired to the 4 pin resistor, but no sign of the Accel resistor.

OK original alternator, good.

Yes the fan is gone, fixed mechanical now.

I’ll have to go through where I had got to on this on my other post in the morning. The previous owners made a few changes like the ECM and relocating the battery etc which all have their own reasons for how they were done, but are hard to tie up with the original schematics.

 

[Righty]

Right I’ve got to get some beauty sleep, thanks all, as usual plenty of useful thoughts from you all. Cheers.

 

[Bewy]

This is where a little electrical knowledge can be dangerous.....
With mechanical things, like a noisy valvetrain, you can hear things....& you can see an oil leak.
With electrical, you cannot see the electrons, you can only see/hear the results. So some expert knowledge is reqd to visualise & interpret from the symptoms what the problem may be.

A fully charged battery at room temp is 12.6-12.7v. A battery that has been charged up may read slightly higher immediately after charging due to the surface charge. Therefore, the battery should be left for a couple of hrs for this charge to dissipate & get a true reading.

 

[peedee]

Hi just a quick question is the car you are dealing with the CL charger in your profile pic, if it is I can send you copies of the wiring diagrams from the factory service manuals which may make it easier to track factory from add on wiring

 

[Dave999]

Is that you Matt?

stalling when you put it into drive....
cut out when you put your foot in the brakes
is it a Carter BBD (2bbl) equipped car?

initial timing
auto choke setting
idle mixture for max rpm
is the vacuum advance connected?

1/2 hour disconnecting and reconnecting every ignition related thing from bulkhead (including bulkhead connectors) forward may pay dividends, what is loose what is corroded? clean and put back.
then do the earth strap and the negative cable to the body from battery, pop into halfords and get a box of spiky washers to make good connections with body mounted ground wires

break out the multimeter later if it doesn't work.

if it is electrical the problem will be in the last 6 to 8 inches of each wire, anything still in factory wrapping will be surprisingly ok once you get back under the the loom wrap, provided there has never been a serious smoke inducing fault, on a warm day some of it is even quite flexible
if its the car i think it is, its been in the UK for a long time.... we didn't until recently have the kind of weather that bakes and ruins car wiring, what we do have is the kind of weather that causes the connectors to corrode and get resistant and the first few inches under the insulation on exposed wires goes grey/green, and worse the closer they are to the battery, with its acidic breath. a cold damp morning in bristol, 57 years in the future was not on the mind of the guy who designed the system, he expected the car to be scrap by year 10.

is yours US made (Hamtramck plant) or South African? if the former its a top-end trim level car, all the bells and whistles, they were selling them at a greater cost than a Jaguar so no poverty pack base model stuff was imported. the original purchaser had money to spend on disk brakes thicker torsion bars, a V8 and chrome on the dash.



Dave

 

[Righty]

Hi just a quick question is the car you are dealing with the CL charger in your profile pic, if it is I can send you copies of the wiring diagrams from the factory service manuals which may make it easier to track factory from add on wiring

Hi no unfortunately that's a far younger version of me, this is for a 69 Barracuda. Thanks though. I hear it's a bit nippy down there at the moment, then again it's pissing down here.

 

[Righty]

Is that you Matt?

stalling when you put it into drive....
cut out when you put your foot in the brakes
is it a Carter BBD (2bbl) equipped car?

initial timing
auto choke setting
idle mixture for max rpm
is the vacuum advance connected?

1/2 hour disconnecting and reconnecting every ignition related thing from bulkhead (including bulkhead connectors) forward may pay dividends, what is loose what is corroded? clean and put back.
then do the earth strap and the negative cable to the body from battery, pop into halfords and get a box of spiky washers to make good connections with body mounted ground wires

break out the multimeter later if it doesn't work.

if it is electrical the problem will be in the last 6 to 8 inches of each wire, anything still in factory wrapping will be surprisingly ok once you get back under the the loom wrap, provided there has never been a serious smoke inducing fault, on a warm day some of it is even quite flexible
if its the car i think it is, its been in the UK for a long time.... we didn't until recently have the kind of weather that bakes and ruins car wiring, what we do have is the kind of weather that causes the connectors to corrode and get resistant and the first few inches under the insulation on exposed wires goes grey/green, and worse the closer they are to the battery, with its acidic breath. a cold damp morning in bristol, 57 years in the future was not on the mind of the guy who designed the system, he expected the car to be scrap by year 10.

is yours US made (Hamtramck plant) or South African? if the former its a top-end trim level car, all the bells and whistles, they were selling them at a greater cost than a Jaguar so no poverty pack base model stuff was imported. the original purchaser had money to spend on disk brakes thicker torsion bars, a V8 and chrome on the dash.



Dave

It is Dave. Funny you're in Twickenham, I live in a village called Tickenham.
It's got a 4BBL Holley but yes it sometimes stalls into drive or reverse, not so much with foot on the brake. The advance is connected, no auto choke and manual choke will usually get it started if cutting out. But there has been some cutting out once the key was released as well which lead me to look into the ballast resistor side of things, which then lead to seeing that that is wired slightly oddly and just in general there has been a fair bit of changing, mainly I imagine to accomodate the later ECM conversion, battery in the boot, electric fan etc.
I think the consensus I'm picking up is that multimetering circuits without knowing the condition of the wiring and connectors etc is perhaps putting the cart before the horse! So I think as you and others above have suggested a bit of general visual checking would be a better starting point, I think I will also use that as the time to unwrap some of the later wiring and see what has gone where and notate an original wiring diagram.
Without making excuses I'm starting at zero knowledge wise but you have to start somewhere. I have considered the option of a new engine / headlight harness from Evans or M&H but again thats getting ahead of myself.

Yes its a Hamtramck car, with a Valiant RHD dash similar to the VF / VG Aussie Valiants, I've put the original steering wheel back in. Sadly there's no fender tag but I know it was originally F8 metallic green, which it still is on the inside, it then was a dark green which is what is on the inside of the doors and I think the white vinyl trim is original. KH discs and 10" drums. Overall its a solid well looked after car Sticky had it for 36 years, it just needs a bit of love in a few areas.

 

[Dave999]

are sure its not your ignition lock switch.

car might have been owned by a security guard.... massive bunch of keys swinging, wears out the lock and the switch contacts

take it out
do not remove wires
start car
vibrate wobble and jiggle the switch lock and keys

if it cuts out....... etc

if it was ballast it works or it doesn't

loose or corroded connection or knackered switch is my guess

and many times my guesses are wrong but that's where i'd start

I think I've seen that car at many shows over the years... appears to have got there a back.... can't be too far wrong...just old..

the only other thing i've had similar was a pickup in the distributor that intermittently stopped working, some kind of heat related short or disconnect in the coil.... worry about that kinda thing later

Dave

 

[Righty]

Yes it's an intermittent issue, I had wandered if it was a sign of the resistor starting to fail but the ignition would be the starting point of the circuit so checking there first is a good place to begin. He used to tow his Duster tube framed race car behind the Barracuda and then at the end of the weekend he'd run the Barracuda in the stock class, that and towing a caravan!

 

[Mattax]

But there has been some cutting out once the key was released as well which lead me to look into the ballast resistor side of things, which then lead to seeing that that is wired slightly oddly and just in general there has been a fair bit of changing, mainly I imagine to accomodate the later ECM conversion, battery in the boot, electric fan etc.

The battery in the boot is another big change.
Begin with visually finding the circuits and supplement that with continuity.
By continuity I mean this:
You find a wire at one location and want to know if it connects to a wire at another location. With the car's battery disconnected, use the ohm setting on the multimeter. If the wires connect it will show low resistance, if the wires don't connect at all it will show infinate resistance. Some meters have a continuity option. These will beep when there is continuity. A third method is a continuity checker which is simply a small light bulb and battery with wire leads.

Knowing the factory circuits will help in figuring out the modifications.
Here's a little summary of the wiring concept. The car has two power sources, the alternator and the battery. They're connected together with the main feeds at a welded junction. All of those wires are 'hot' when the battery is connected.

The battery stores energy at no more than 12.8 Volts. It may read a little higher after charging, but that's just on the surface.
Electrons flow from the battery during start and when the alternator circuit can't. Magnetism created by the electrons moving to (or from) the battery to the main junction deflects the needle in the ammeter.

When the engine is running, the alternator produces power at roughly 14 Volts. It becomes the source of power. Imagine if you have a cistern feeding a pipe at 12 psi and a water pump feeding the same pipe at 14 psi.

The naming convention on the wire diagrams is like this:
A bAttery
R alteRnator
J1 Feed to Ignition switch
J2 Ignition circuit (run the engine and alternator)
J3 Ignition start (bypass the ballast resistor during start)
Q Accessory feeds.


To summarize:
Begin at the battery. Identify the wires at its positive and earth terminals. Find where they go.
Then do the same at the alternator. (IIRC in '69 power for the horn relay may still be connected at the alternator)
Trace the connections for the ignition run and start circuits.
Finally, IIRC since there was something interaction with the gear selector, check the run to the neutral safety and reverse light switch.

Tips for removing the bulkhead connector engine side. question on the main harness plug on firewall

How the alternator and regulator work

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

 

[Daves69]

OK original alternator, good.

But I can't see if its a grounded field or not.

@Righty ....
Not to sidetrack, I'm just curious. Are both fields being used on your set up or is one grounded?

 

[Mattax]

@Righty ....
Not to sidetrack, I'm just curious. Are both fields being used on your set up or is one grounded?

I take back what I posted about not being able to see the second terminal.

Grounded

It looks like the capacitor is an add on.

 

[67Dart273]

Yes it's an intermittent issue, I had wandered if it was a sign of the resistor starting to fail but the ignition would be the starting point of the circuit so checking there first is a good place to begin. He used to tow his Duster tube framed race car behind the Barracuda and then at the end of the weekend he'd run the Barracuda in the stock class, that and towing a caravan!

Resistors seldom fail intermittent. Most the time they are good or bad. However, the terminals/ wire connections can be oxidized / loose, and THEY may be a problem, not only where they push on,, but the crimps to the wires

 

[67Dart273]

Easiest way to confirm an actual 5 pin box is to trace and remove the 5th wire from the ballast. The presence of a 5th pin does not tell you. I can be a dummy

If it stops running--you have a 5 pin box. Also make certain your ballast is connected correctly. I guess you know there are two resistors in there. the "U" cutout at one end of the ceramic is how you index the resistor for proper connections.

If possible I would get back to an OEM style coil, at least until you get this sorted.

make DARN sure the box is well grounded. Scrape around the mounting holes, firewall and box, and use star lock washers. Some guys add a separate ground pigtail. Same treatment needs done for the VR

I would "rig" a wire off the key feed side of the ballast, and temporarily run that so you can monitor voltage when running. Watch for a V drop if it quits. You can buy those little branch adapters for the push on flag terminals, so you can add a connection, like these

Stackable 1/4" Push-On Terminal Adapter - 16-14 AWG - CMFP-1614

This vinyl-insulated male/female push-on terminal adapter connects lights or accessories to a terminal block. The 1/4" piggyback-style connector easily fits onto a push-on tab and also has a male blade for stackable wiring on 1 terminal.

www.superbrightleds.com

Another trouble on old wiring/ old distributors is oxidation in the dist connector. There is almost zero current flow so nothing to "push" past corrosion. "Work" the connector in/ out several times to scrub the terminals and feel for tightness. If you can get a .17 cal rifle bristle brush (bb gun size) some of those brushes will fit those connectors, the ECU, the later VR connector, and here, we use those flat trailer connectors.

Speaking of connectors, it ALSO could be the same cause in the ECU connector.

 

[67Dart273]

Another thing to tuck away in your mind is possible drop in the "run" circuit, which includes the ammeter/ bulkhead connector terminals. THIS ALSO affects charging voltage, because drop in this circuit causes the VR to ramp up voltage.

To check this, connect your meter to the key side of the ballast, and the battery positive post. You can either extend the meter wire, or measure the batt first, to ground for a reference, and then do this test from the ballast to ground, and subtract

Turn the key to "run" with engine stopped. You can read the drop directly. Wiggle the key and see if it changes substantially. If the drop is more than .3V or so (3/10 of one volt) look for the issue. This can be anywhere or a combination, in the path from the battery, through the ammeter circuit, through the key switch, and back out on the "run" line.

One easy way around this is to cut the dark blue "run" feed coming out into the bay, before it branches off. Use the firewall end to trigger a relay, feed the relay from a fused/ breaker no12 off the start relay, and then connect the switched contact to the engine bay end of the cut dark blue. This will then feed the ignition/ VR right off that start relay stud, and greatly shorten and improve the path.

 

[Daves69]

......THEY may be a problem, not only where they push on,, but the crimps to the wires

I do believe I had this very scenario with my FL. Intermittent disconnect.
I stripped my fusible link expecting to find a visual open. Nope, no soap.
Checking the ends I found the bulkhead side would go open as I move the wire just a bit.

 

[Righty]

Well I think I have a bunch of things I can take a look at this weekend, we're a bit hectic here as we are just about to put our house on the market, so apparently I "need to stay focussed!" like I'm ever anything else, just depends what I think I need to focus on. I will follow the advice here to check out actual physical connections wiring runs first before i start confusing myself with meter readings etc, I did notice last night that the terminals /pins on the ballast resistor are a little wobbly so I will probably put in the new resistor I have. Once I have had time I'll try to get back with some more pictures maybe a diagram showing what I have traced.
Thanks again everyone, I really appreciate the level of knowledge and willingness to share it on here.