Voltage drop at ballast resistor

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Paladin06 said:

Also I noticed the red wire at the bulkhead under the dash gets noticeably warm while making these test.
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THAT is the biggest clue yet. You very likely have a bad terminal (connection) right there a the bulkhead connector, either between the two terminals, or between one terminal and the wire it's connected to
 
Paladin06 said:
* For your own education, measure the voltage across the battery while charging. (13.24 volts)
My cars stay on a trickle charger all the time.

* Measure Voltage at Battery Positive (13.04 volts) *, Alternator Output (Bat) (12.96 volts), and Bulkhead at Red Battery (12.88 volts),
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Good. 13.24 Volts brings up the battery's surface charge. The reason the voltage goes down at each point you measured is probably entirely due to the surface charge dissipating.

Paladin06 said:
Black Alt, (1.4 volts)
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This must be a typo or a bad reading.
Paladin06 said:
Blue Run. (0 volts)
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As we expect. So far so good - except if that Alternator output connection reading is real - which the only way it could be is if its a loose connection and got worse when probed. Does that make sense? Everything in the main run should be at battery voltage.

Main_charging_wires_Test-Off.png
 
Mattax said:
Good. 13.24 Volts brings up the battery's surface charge. The reason the voltage goes down at each point you measured is probably entirely due to the surface charge dissipating.


This must be a typo or a bad reading.

As we expect. So far so good - except if that Alternator output connection reading is real - which the only way it could be is if its a loose connection and got worse when probed. Does that make sense? Everything in the main run should be at battery voltage.

View attachment 1715165769
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This must be a typo or a bad reading.
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This reading was at the bulkhead under the hood.
 
Paladin06 said:
* Note current flow through Ammeter. Should be around 5 amps discharging (3-4 to alternator field, 1-2 to coil and ECU). (Yes I'd say 5 amps)
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Good.
Paladin06 said:
* Measure Voltage at Battery Positive, (12.10 volts) Alternator Output (Bat), (11.12 volts) Red Battery at Starter Relay, (12.22 volts) and Bulkhead at Red Battery, (11.81 volts) Black Alt, (11.47 volts) Blue Run (10.47 volts).

* Recheck Voltage at Battery Positive.* Observe ammeter. Write down any change from first turning on ignition. (No noticeable change)
Additionally I checked voltage at the back of the amp gage and it was 11.47 at both post.
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I've put this on the drawing...
Paladin06 said:
These numbers seem all over the map to me but with 3 back surgeries they are the best I can do.
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They're fine. Lets look at what they show.
12.1 Volts at the battery under a 5 amp load. OK. especially seeing the next reading down the line.
12.2 Volts at Starter Relay.
11.8 Volts at Bulkhead. 0.4 Volt drop in the wire is a lot. If real, could be a bad crimp connection at either end or the fusible link splice, (corroded or broken strands ).
11.5 Volts on both sides of the Ammeter and at the Alternator connection. No loss to speak of from the battery wire to the main splice. (Since there is no load and no current in the black wire to the alternator - it can not be assumed the alternator's bulkhead connection is good.)
10.5 Volts at Run. Must be resistance between the main splice and this connection.

Paladin06 said:
After I completed all the test, I checked the voltage at the blue wire on the resistor. It was 10.47. It is now 9.58. WTF???

Also I noticed the red wire at the bulkhead under the dash gets noticeably warm while making these test.
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Sounds like a loose connection or a wire with bad insulation? Is the red wire is the one from the main splice to the ignition switch?
If that's warm with just 5 amps, that's a major problem.

Main_charging_wires_Test-On.png
 
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Paladin06 said:
This must be a typo or a bad reading.
↑
This reading was at the bulkhead under the hood.
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Well something isn't right. Can't have 13 volts at the Alternator stud and battery but just 1.4 volts at the bulkhead connection.
If its real, something is loose and making intermitant contact. Or worse, there is a chafed wire and its grounding. But if was shorting on the main splice side of the ammeter - you'ld see the ammeter bounce to higher discharge whenever it contacted.
 
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Paladin06 said:
This the red wire to the amp meter.
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You found a small voltage drop in that section. Very much agree the heat is a big clue. 5 amps in that wire should not heat it any more than the other 10 and 12 gage wires.

I'd start looking for bad connections and green oxidized wire from the relay to the ammeter.
Definately remove the connectors and pop out the metal terminals. Its not that hard. Take your time.

Same thing with the blue run wire connector and terminals. The drop you found there is even worse. Problem(s) also could be at the start switch, or worst case, the main splice. So check the whole run.

Does that make sense?
 
Mattax said:
You found a small voltage drop in that section. Very much agree the heat is a big clue. 5 amps in that wire should not heat it any more than the other 10 and 12 gage wires.

I'd start looking for bad connections and green oxidized wire from the relay to the ammeter.
Definately remove the connectors and pop out the metal terminals. Its not that hard. Take your time.

Same thing with the blue run wire connector and terminals. The drop you found there is even worse. Problem(s) also could be at the start switch, or worst case, the main splice. So check the whole run.

Does that make sense?
Click to expand...

Please explain below:
I'd start looking for bad connections and green oxidized wire from the relay to the ammeter.
Definately remove the connectors and pop out the metal terminals. Its not that hard. Take your time.

Under the hood on under the dash?
 
Mattax said:
Good.

I've put this on the drawing...
They're fine. Lets look at what they show.
12.1 Volts at the battery under a 5 amp load. OK. especially seeing the next reading down the line.
12.2 Volts at Starter Relay.
11.8 Volts at Bulkhead. 0.4 Volt drop in the wire is a lot. If real, could be a bad crimp connection at either end or the fusible link splice, (corroded or broken strands ).
11.5 Volts on both sides of the Ammeter and at the Alternator connection. No loss to speak of from the battery wire to the main splice. (Since there is no load and no current in the black wire to the alternator - it can not be assumed the alternator's bulkhead connection is good.)
10.5 Volts at Run. Must be resistance between the main splice and this connection.


Sounds like a loose connection or a wire with bad insulation. Is the red wire is the one from the main splice to the ignition switch?
If that's warm with just 5 amps, that's a major problem.

View attachment 1715165781
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OK with the switch on and bulkhead connector removed as I said earlier I get 11.8 volts at the blue wire with fusible link. If I disconnect the fusible link from the red wire leading from the starter relay I get the same voltage reading as the battery. Bad fusible link maybe? What tool is required to remove the pins from the bulkhead connector. I want to replace the fusible link.

Thx again.
 
Paladin06 said:
Please explain below:
I'd start looking for bad connections and green oxidized wire from the relay to the ammeter.
Definately remove the connectors and pop out the metal terminals. Its not that hard. Take your time.

Under the hood on under the dash?
Click to expand...
Where ever the voltage dropped when current was run through it. Ignoring whatever variations there are in the readings, there was a .5 Volt drop between the relay and the whereever you read it on the bulkhead, and another .3 Volt drop to the ammeter. Since that wire is warm its more suspect.

Then there's a 1 Volt drop between the Ammeter and the run wire connection at the bulkhead.

The .4 Volt drop to the alternator's stud makes no sense unless there's a short inside. If there was a short inside, it should have shown up in the measurements with the ignition off.

Main_charging_wires_Test-On-result.png
 
Paladin06 said:
OK with the switch on and bulkhead connector removed as I said earlier I get 11.8 volts at the blue wire with fusible link. If I disconnect the fusible link from the red wire leading from the starter relay I get the same voltage reading as the battery. Bad fusible link maybe? What tool is required to remove the pins from the bulkhead connector. I want to replace the fusible link.

Thx again.
Click to expand...

Disregard this last comment. The voltage is the same through the fusible link to the bulkhead connector. Been messing with this thing since 0700 this morning. My back is killing me. Going to take 2 oxy and chill.

Thx all.
 
Mattax said:
Where ever the voltage dropped when current was run through it. Ignoring whatever variations there are in the readings, there was a .5 Volt drop between the relay and the whereever you read it on the bulkhead, and another .3 Volt drop to the ammeter. Since that wire is warm its more suspect.

Then there's a 1 Volt drop between the Ammeter and the run wire connection at the bulkhead.

The .4 Volt drop to the alternator's stud makes no sense unless there's a short inside. If there was a short inside, it should have shown up in the measurements with the ignition off.

View attachment 1715165836
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Paladin06 said:
Disregard this last comment. The voltage is the same through the fusible link to the bulkhead connector. I still am not getting any reading at the black wire to the bulkhead connector. Been messing with this thing since 0700 this morning. My back is killing me. Going to take 2 oxy and chill.

Thx all.
Click to expand...

After cleaning the corroded fusible link connection I now have the same 12.3 volt reading at the bulkhead connector, the starter relay and the battery.
 
Mattax said:
Where ever the voltage dropped when current was run through it. Ignoring whatever variations there are in the readings, there was a .5 Volt drop between the relay and the whereever you read it on the bulkhead, and another .3 Volt drop to the ammeter. Since that wire is warm its more suspect.

Then there's a 1 Volt drop between the Ammeter and the run wire connection at the bulkhead.

The .4 Volt drop to the alternator's stud makes no sense unless there's a short inside. If there was a short inside, it should have shown up in the measurements with the ignition off.

View attachment 1715165836
Click to expand...

I have no reading at the alternator stud or the wire at the bulkhead connector.
 
E459ADB1-2EA2-4DB7-B6B6-468F4AA4A9C2.jpeg
Couldn't sleep a wink last night so I got up and studied this thread from the beginning. A couple of questions.
1.With the four pole ECU do I really need the four pole ballast resistor? I was told some years ago on this forum I did not. This is what my resistor looks like today.
2. Most diagrams provided and the shop manual show the red wire from fusible link to the bulkhead connector. My fusible link is tapped into the bulkhead connector, with the red wire at the starter relay to the fusible connector. Is this an issue?
3. Does anyone have a DYI or know of a video for replacing the ignition switch?
 
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2....Can you re--describe this? Or photo? Can't "get" what you are trying to convey

All you are doing, here, is providing power from the starter relay stud---which is also a junction point "battery"..........through the fuse.........to the bulkhead. There may be minor variations over the years about the wire "makeup."
 
67Dart273 said:
2....Can you re--describe this? Or photo? Can't "get" what you are trying to convey

All you are doing, here, is providing power from the starter relay stud---which is also a junction point "battery"..........through the fuse.........to the bulkhead. There may be minor variations over the years about the wire "makeup."
Click to expand...

I’m sorry did you read through the thread? The issue is trouble shooting voltage drop at a number of locations
 
Paladin06 said:
I’m sorry did you read through the thread? The issue is trouble shooting voltage drop at a number of locations
Click to expand...


I don't understand what you are trying to describe with the fuse link.....what is the suspected issue with the physical wiring? Your statement


"2. Most diagrams provided and the shop manual show the red wire from fusible link to the bulkhead connector. My fusible link is tapped into the bulkhead connector, with the red wire at the starter relay to the fusible connector. Is this an issue?"

is what I don't understand
 
I don't understand either.
"most diagrams provided" If you mean what I posted here - those are by Nacho and the wire colors should just be considered generic.
The only one that is likely to be completely correct, is the one in the service manual for your year. If you have, post a picture of the it becuase I don't have '72 FSM in print or digital.
But in the photo above, the harness has been modified - certainly the connectors changed and at least one wire taped off or ? So it looks modified. What else is modified?

"tapped" In this context, its generally understood as a side tap. Often the quick and dirty squeeze type connectors. Maybe Del reads it the same way. Its very confusing.
 
Gentlemen I’m sorry if I confused or upset any of you. You help is so much appreciated and I am forever greatful. We will get Cherry fixed and I will have you all to thank. Due to physical limitations I have to go slow and the pain meds do take their toll. I just ask that you hang with me. We will get there.

Thx

Greg A
 
Quite all right. I'm partially disabled at 69, myself, with arithritic like conditions, and in particular, neck problems. "Crawling around" under a dash is VERY tough on this old guy

The last several "gist" of what you have posted indicate that it's all "right there" in/ at the bulkhead connector or the under-dash harness. Might be time to find a (younger LOL) local friend/ help to help pull the cluster and access things.

I waste no time........I pull the seats!!!!
 
So you disagree. It is confusing on my end.
Take your time. Underdash is never fun. Leaning over the fender gets to me too after a while.
 
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