Ignition 1 “Run” shorted?

Moparfiend · Jan 27, 2019

I have bypassed my ignition 1 run to an external switch in order to solve a high current short in my Brown Ignition 1 run line. I have ohmed out both sides of the Molex car bat disconnected and neither has any resistance to ground. I am hoping someone has had the same problem that can suggest something I am missing. I am using a new ignition harness column lock side.
Pictures:

Moparfiend · Jan 27, 2019

Another side of connection

PurpleBeeper · Jan 27, 2019

Check your wiring diagram, but it "looks" like the circuit with the short is the large red wire (main battery power going to ignition switch).

Anyway, the blue & brown wire having infinite resistance (not going to ground) is I think what you'd want (?). You would also be looking for infinite resistance between both the blue & brown wires to that melted large red circuit (to make sure they're not crossed).

In order to "hot wire" your car (sounds like what you want), you need 12V (with 20A fuse & on/off switch) coming from the battery & going to where the blue wire connects on the "in side" of the ballast resistor. For the brown wire, run another 12V wire (with 20A fuse & momentary on push button) coming from the battery & connected to the "out side" of the ballast resistor where the brown wire connects.

Moparfiend · Jan 27, 2019

PurpleBeeper said:
Check your wiring diagram, but it "looks" like the circuit with the short is the large red wire (main battery power going to ignition switch).

Anyway, the blue & brown wire having infinite resistance (not going to ground) is I think what you'd want (?). You would also be looking for infinite resistance between both the blue & brown wires to that melted large red circuit (to make sure they're not crossed).

In order to "hot wire" your car (sounds like what you want), you need 12V (with 20A fuse & on/off switch) coming from the battery & going to where the blue wire connects on the "in side" of the ballast resistor. For the brown wire, run another 12V wire (with 20A fuse & momentary on push button) coming from the battery & connected to the "out side" of the ballast resistor where the brown wire connects.

Thanks PB, yes I have an open circuit on the brown wire, which is correct ie not shorted to ground.
Running an MSD box and have a 12V switch for Ignition 1 run. The brown wire is severes at the connector so its not connected to the ignition switch anymore. I have 500mA draw while @Ignition 1 is energized. 0 current draw all off.
I see the red wire lookes damaged/ melted but I believe that is due to proximity to the hot brown wire. I could be wrong though.
Here is the impedance measurements to ground with the ignition harness disconnected and measured at the other connector (again not the ignition harness side)
Voltage at Molex connector (other side of ignition sw)
Yellow start shorted !
Black acc open
Purple white stripe ignition 2 shorted !
Brown ignition 1 open
Red battery shorted!
Orange lamps shorted!
Red buzzer shorted!
Red buzzer shorted!

Moparfiend · Jan 27, 2019

With a hot wire ignition 1 car starts with the key and runs but I think it’s burning up the harness. Still trying to see if Bubba was involed.

400sforever · Jan 27, 2019

I've got a car with a bubba wiring job done to it except mine starts on ignition 2. . As soon as I let off the key it starts. Very weird. It used to start normal with the key. I check wiring around the ballast resistor and changed the resistor but still no luck yet

kiwigtx · Jan 27, 2019

Has the Ammeter wiring been touched....the wires may be loose on the back of the gauge, and shorting out there.

Billccm · Jan 27, 2019

I use a test lamp in this situation
It glows bright while the short is in circuit
Then pull branches of connectors tracing the short
In your case I bet it's a pinched wire to chassis or sheetmetal

PurpleBeeper · Jan 27, 2019

Just thinking out loud here...
1. Both the brown & the blue wire should be connected to the smaller red wire on your MSD box. The brown is hot during "start" & the blue is hot during "run". (400sforever, you have a problem with your brown wire).
2. Black accessory open - sounds correct unplugged
3. Purple/white - ?
4. Red battery - ? Does it have 12V at this connector? The "short" might just be the connection to the battery.
5. Orange/lamps - "short" might be correct....since the orange wire is grounded through a bunch of interior lights.
6. 2 Red buzzer wires - I would "expect" one wire to show 12V and the other one to show ground.
7. You might want to check continuity between each of the wires, especially vs. the melted red one, to see if they're "crossed" inside the harness.

Moparfiend · Jan 27, 2019

400sforever said:
I've got a car with a bubba wiring job done to it except mine starts on ignition 2. . As soon as I let off the key it starts. Very weird. It used to start normal with the key. I check wiring around the ballast resistor and changed the resistor but still no luck yet

Hey bub start your own theead I an confusing enough

Moparfiend · Jan 27, 2019

kiwigtx said:
Has the Ammeter wiring been touched....the wires may be loose on the back of the gauge, and shorting out there.

The dreaded Ameter looks ok.

Moparfiend · Jan 27, 2019

Billccm said:
I use a test lamp in this situation
It glows bright while the short is in circuit
Then pull branches of connectors tracing the short
In your case I bet it's a pinched wire to chassis or sheetmetal

Thanks Bill. I have a bice Fluke DMN. I have to look at the fuse box in detail. It might be a piched wire. Will advise.

Moparfiend · Jan 27, 2019

PurpleBeeper said:
Just thinking out loud here...
1. Both the brown & the blue wire should be connected to the smaller red wire on your MSD box. The brown is hot during "start" & the blue is hot during "run". (400sforever, you have a problem with your brown wire).
2. Black accessory open - sounds correct unplugged
3. Purple/white - ?
4. Red battery - ? Does it have 12V at this connector? The "short" might just be the connection to the battery.
5. Orange/lamps - "short" might be correct....since the orange wire is grounded through a bunch of interior lights.
6. 2 Red buzzer wires - I would "expect" one wire to show 12V and the other one to show ground.
7. You might want to check continuity between each of the wires, especially vs. the melted red one, to see if they're "crossed" inside the harness.

Thanks PB. I will study this and advise. As I mentioned to Bill I am going to take the fuses out to help isolate the lines that look shorted.

72RoadrunnerGTX · Jan 27, 2019

Keep in mind, the Molex terminals at the ignition switch connector will build up resistance and create excessive heat under normal loads after all these years. The brown wire (ignition2)is the ballast resistor bypass and would only have coil current while cranking only. The measurement posted shows no load present on the brown wire at rest. The picture shows that most of the heat damage is at the red wire main power feed. Again, fairly common on these cars. Replace the Molex connectors with something that can handle the normal current loads.

These are Anderson Powerpoles, reduced the voltage drop on ignition1, while runing, by a full volt over the undamaged 48-yearold Molex connector they replaced.

Moparfiend · Jan 27, 2019

72RoadrunnerGTX said:
Keep in mind, the Molex terminals at the ignition switch connector will build up resistance and create excessive heat under normal loads after all these years. The brown wire (ignition2)is the ballast resistor bypass and would only have coil current while cranking only. The measurement posted shows no load present on the brown wire at rest. The picture shows that most of the heat damage is at the red wire main power feed. Again, fairly common on these cars. Replace the Molex connectors with something that can handle the normal current loads.

These are Anderson Powerpoles, reduced the voltage drop on ignition1, while runing, by a full volt over the undamaged 48-yearold Molex connector they replaced.

View attachment 711467

Those look like good connectors. I will obviously need to replace the connectors so I will look at these. Thanks 72RR

Nacho-RT74 · Jan 28, 2019

72RoadrunnerGTX said:
The brown wire (ignition2)is the ballast resistor bypass and would only have coil current while cranking only.

Just for clarifying because depending on how is being checked it can cause confusion: yes, from ign switch but while the ballast is conected and everything working, this wire will be hot too ( at lower voltage rate but still hot )

72RoadrunnerGTX said:
The picture shows that most of the heat damage is at the red wire main power feed. Again, fairly common on these cars.

Totally agreed. Red wire on this systems tends to be overheat on Red and Black wires ( acc ) this last specially on A/C cars and aftermarket adds... and SOMETIMES the blue ( RUN or Ign1 ).

If stock look is important, new molex terminals are available around at electrical suppliers, but plastic piece not so easy to get, althought getting a new ign switch will get the brand new female end.

if not, the terminals shown by 72RoadrunnerGTX are bullet proof pieces to the function.

wow! I didn't know they clip one to the other! that's amazing! I just had seen them individually hanging around. I have thought on these to the fuse link since I haven't seen able to find a single way molex plug to keep the stock piece!

Nacho-RT74 · Jan 28, 2019

red key buzzer wires... being 70 ( by the avatar ) it drives positive I think ? if so, one should hot and the other not, but open ( no signal ) running to buzzer. Since 71 they drive negative ( fortunatelly ).

Time to check how is your brown wire conditions at splice for the MSD. You won't find anything at fuse box related with brown wire circuit, The brown wire circuit is a straight on line up to ballast, then to coil and that's all. If something made to fail this, is just related to that area. If failed like that there is a big problem because brown wire doesn't sucks really a load to ever think on use the Molex terminal they used. It could be used even the next small size.

I must say that IS NOT MANDATORY to splice blue and brown wires to feed MSD modules, because this signal is just a remote trigger to turn it on. Existant coil wire signal is quite enough to make it work still with ballast in place with the voltage provided. This is an exception just for RTR distribuitors, any brand.

For 400sforever: check bulkhead. It seems the brown line is cut or loosen somewhere.

The brown wire also feeds the ECU while cranking through the Ballast, energizing the blue Ign 1 RUN circuit. But if starts as soon you release the key Ballast is good because a damaged ballast won't start in anyway, being the ECU not sourced while cranking, or being the coil not sourced while in RUN

Moparfiend · Jan 28, 2019

Thanks guys. I currently have the brown wire ((Ignition 1 run) bypassed from the MSD to a remote seitch.
It starts with the ignition key just fine. You can see by the close up that the brown wire was clearly over currenting. I think however I have multiple issues. That I have to sort out because the red wire must also be overcurrenting (after all it was shorted to ground). I unfortunately still not able to work very long on ot due to health issues but will try to divide up the issues the fix them. Will still need your advice as I move through it. I will teplace the crap stock Molex connectors with something more robust like the Power Ploes.

Nacho-RT74 · Jan 28, 2019

it is REALLY weird an overheat like that on brown wire terminal! they usually don't get a load able to make that!

Red wire can be "shorted" to ground through dome light bulb ( and map light if optioned ) if you checked with open door and bulb installed. Remember a bulb is a controlled short

72RoadrunnerGTX · Jan 28, 2019

Moparfeind said:
I currently have the brown wire ((Ignition 1 run) bypassed from the MSD to a remote seitch.
View attachment 711745 View attachment 711746 View attachment 711747

For clarification, the brown wire is identified as Ignition 2 in all factory technical info. The blue with tracer is ignition 1.

In post #4, you indicate a measured 500ma current draw with the key in the run position and 0 current draw in the off position. MSD? Are you sure the heat damage was not present prior to the MSD install?

Red wire shorted? Are you measuring resistance with a DVM at the dash harness ignition switch Molex? If so, you will measure grounds through any other unswitched loads on that circuit. If it was dead shorted, you would know it within a second or so after the battery is connected, there would be smoke somewhere.

Ignition 1 “Run” shorted?

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