Question about ignition switch"start" and "run" outputs

WissaMan

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Is the ignition switch supposed to put out 12v at both the "start" and "run" side of the ballast resistor when the key is in the "start" position?

This is a 68 300. I tried to find this info in the FSM but could not.
 
Is the ignition switch supposed to put out 12v at both the "start" and "run" side of the ballast resistor when the key is in the "start" position?

This is a 68 300. I tried to find this info in the FSM but could not.

It is 12v on both leads, the ballast resister will drop the voltage in the run position. The start position is only active with the key at start to by pass the resistor.

Dave
 
Okay, so if we don't get 12v on the "run" lead when the key is in the start position, but do get it when the key is in the run position, am I correct that would indicate a faulty ignition switch?
I believe that is normal, at least for a 66 model.
 
Okay, so if we don't get 12v on the "run" lead when the key is in the start position, but do get it when the key is in the run position, am I correct that would indicate a faulty ignition switch?

Just to be sure we are on the same page...

Disconnect the ballast resistor to get that out of the loop. With the key in "start" position, you should get 12 volts at the brown wire. With the key in "run" position, you should get 12 volts at the blue wire.

You won't get 12 volts on the brown (start) wire with the key in the "run" position.
 
Just to be sure we are on the same page...

Disconnect the ballast resistor to get that out of the loop. With the key in "start" position, you should get 12 volts at the brown wire. With the key in "run" position, you should get 12 volts at the blue wire.

You won't get 12 volts on the brown (start) wire with the key in the "run" position.
I think what he's really asking is, with the key in the START position, should there be 12V on the blue (run) wire? I believe the answer is NO.

I recall connecting a Painless auxiliary fuse panel with some relay-activated circuits. I was going to tap the relay into the blue (run) wire. I disconnected the ballast wires and checked with my voltmeter or a test light and there was no power to the blue wire with the key in START. With the ballast resistor connected however, there was enough voltage feeding back from the brown wire through the ballast resistor to keep the relay energized during START. So that's how I wired it.
 
Mike is correct. And my reason for asking is similar to his, except in our case it's because we installed the Mancini HiPo electronic ignition kit a few weeks ago and everything seem to go flawlessly. Engine started and ran on the first try, set the base timing, road tested, etc.

Then when we went to start the car a week or two later, it would crank but not start. Yet you would hear a brief stumble when giving up on the cranking and switching the ignition key to OFF. Then I discovered that if you cranked it a bit and then just let the key drop back to RUN position, it would start and run. But then to make things even more odd, after we let it idle for a while, it would start while cranking as it should.

So we went back out to the car a week or two later again, but this time we double checked all the wiring and tested voltages at various points. What we discovered was that during cranking, the blue wire to the ECU was only getting 6~7 volts, which I'm assuming is not enough for it to work, but when in the RUN position (with the engine not running) it was getting 10 ~ 11 volts. So basically when cranking, the ECU was not getting enough power to work ut when you'd let the key drop back to RUN, the engine was still rotating fast enough that it would catch.

After studying the wiring diagram, I realized that the blue wire being connected according to the instructions was getting it's power through the resistor when key was in the start position, and it just wasn't enough.....until the engine ran a little while after which it would start normally. So I thought -- bad battery (the date on it is 2011) -- yet the engine cranks fine at all times. We took it to autozone and they tested the battery and said it was OK.

So I'm not sure what to think. Bad battery? A bad wires, connection, or bad ignition switch introducing added resistance into the circuit? I was thinking of installing relays to power the ECU directly from the battery but I just now read this article that says you don't even need the ballast resistor with electronic ignition, so I don't know what to think...

Ballast Resistor Guide - Ballast Blast-Off - Mopar Muscle Magazine
 
You probably have a corroded ignition switch or a corroded bulkhead connector. You should be getting a minimum of 12.5 volts to both leads when they are active. I would start with the ignition switch as that is inexpensive and tear into the bulkhead connector if that does not solve the problem. (You can run a resistance test on the ignition switch if unsure of its condition, it is usually easier to do this on a work bench). You can also try running a lead to the run terminal on the ecu to see if it operates normally with the ignition bypassed, that will help isolate the problem.

Dave
 
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It really isn't hard to pop the bulkhead connector apart to inspect it, clean it, and put some De-Oxit in the connections. You certainly don't want to be finding anything like this.
upload_2017-7-22_21-22-17-jpeg.jpg

IMG_5977.jpg
IMG_5977.jpg

You've just got to pop the clips on the sides to pull it apart.
 

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You probably have a corroded ignition switch or a corroded bulkhead connector. You should be getting a minimum of 12.5 volts to both leads when they are active. I would start with the ignition switch as that is inexpensive and tear into the bulkhead connector if that does not solve the problem. (You can run a resistance test on the ignition switch if unsure of its condition, it is usually easier to do this on a work bench). You can also try running a lead to the run terminal on the ecu to see if it operates normally with the ignition bypassed, that will help isolate the problem.

Dave
I replaced my ignition switch with a brand new one and it behaves the same as my old one. No power to the RUN side of the ballast during START.

Also I have bypassed the main power connection in my bulkhead connector so that's not an issue for me. I believe that is normal operation.

If the OP's aftermarket ignition system does not require the ballast in-circuit, it is safe to remove it and short together the two wires to provide full voltage for both START and RUN.
 
I replaced my ignition switch with a brand new one and it behaves the same as my old one. No power to the RUN side of the ballast during START.

If you are getting power to the start side with the key in the start position, I think it should still start. Where do you have the input power to the ECU hooked up? If it wired per manufacturer's specs a problem with the bulkhead connector is the next most likely culprit, see post above.

Dave
 
Mike is correct. And my reason for asking is similar to his, except in our case it's because we installed the Mancini HiPo electronic ignition kit a few weeks ago and everything seem to go flawlessly. Engine started and ran on the first try, set the base timing, road tested, etc.

Then when we went to start the car a week or two later, it would crank but not start. Yet you would hear a brief stumble when giving up on the cranking and switching the ignition key to OFF. Then I discovered that if you cranked it a bit and then just let the key drop back to RUN position, it would start and run. But then to make things even more odd, after we let it idle for a while, it would start while cranking as it should.

So we went back out to the car a week or two later again, but this time we double checked all the wiring and tested voltages at various points. What we discovered was that during cranking, the blue wire to the ECU was only getting 6~7 volts, which I'm assuming is not enough for it to work, but when in the RUN position (with the engine not running) it was getting 10 ~ 11 volts. So basically when cranking, the ECU was not getting enough power to work ut when you'd let the key drop back to RUN, the engine was still rotating fast enough that it would catch.

After studying the wiring diagram, I realized that the blue wire being connected according to the instructions was getting it's power through the resistor when key was in the start position, and it just wasn't enough.....until the engine ran a little while after which it would start normally. So I thought -- bad battery (the date on it is 2011) -- yet the engine cranks fine at all times. We took it to autozone and they tested the battery and said it was OK.

So I'm not sure what to think. Bad battery? A bad wires, connection, or bad ignition switch introducing added resistance into the circuit? I was thinking of installing relays to power the ECU directly from the battery but I just now read this article that says you don't even need the ballast resistor with electronic ignition, so I don't know what to think...

Ballast Resistor Guide - Ballast Blast-Off - Mopar Muscle Magazine
Beware misinformation in that article. The Mopar electronic ignition and the Pertronix Ignitior-1 still require a ballast resistor, at least unless you change your coil to one with an internal resistance. That introdues other complications. HEI and CD ignition systems do not require a ballast resistor.

Note that the Mopar electronic ignition conversion comes with a new ballast resistor, which I believe has a lower value than the factory one. That is the one which should be used with the Mopar ECU.
 
If you are getting power to the start side with the key in the start position, I think it should still start. Where do you have the input power to the ECU hooked up? If it wired per manufacturer's specs a problem with the bulkhead connector is the next most likely culprit, see post above.

Dave
You quoted my post but are you talking to me or the OP? My car has a Mopar ECU originally wired to the RUN side of the ballast. The voltage through the ballast during cranking is high enough to keep a Mopar ECU powered so I never had a problem. More recently I wired-in an auxiliary fuse panel with a relay and was concerned that there would be enough power to keep the relay energized, which there is, so I still do not have a problem.
 
You quoted my post but are you talking to me or the OP? My car has a Mopar ECU originally wired to the RUN side of the ballast. The voltage through the ballast during cranking is high enough to keep a Mopar ECU powered so I never had a problem. More recently I wired-in an auxiliary fuse panel with a relay and was concerned that there would be enough power to keep the relay energized, which there is, so I still do not have a problem.

That was for the OP.

Dave
 
With the key in the START position there should be 12 volts from the ignition switch. The START circuit does not go through the ballast resistor. The system uses the full 12 volts to start the car.

With the key in the RUN or ON position there should be 12 volts from the ignition switch. The RUN circuit runs through the ballast resistor which causes the power to drop. So there is 12 volts into the resistor but less coming out.

There is nothing in the ignition switch to change the voltage running through the switch. It's 12 volts in and 12 volts out. It's the ballast resistor that drops the power.

For more detail, when the key is in the START position power runs through a Brown wire to the resistor. At the resistor a Dark Blue wire should be attached with the Brown. Power runs through the Dark Blue wire to the coil, skipping the resistor. A full 12 volts from the switch to the coil.

In the RUN position, power runs through a Dark Blue wire to the resistor - opposite end of the resistor to where the Brown wire attaches. Power runs through the resistor and then via the Dark Blue wire to the coil. It's a full 12 volts to the resistor, but reduced power from the resistor to coil.

From the above you should understand why, when the ballast resistor dies, the engine will turn over and sound like it is running in START, but when you release the key and the ignition switch goes to the RUN position, everything dies.

A second Dark Blue wire is attached to the resistor with the Dark Blue wire for the RUN position which runs to the IGN connector on the Alternator Regulator. Has nothing to do with what we are talking about.
 
With the key in the START position there should be 12 volts from the ignition switch. The START circuit does not go through the ballast resistor. The system uses the full 12 volts to start the car.

With the key in the RUN or ON position there should be 12 volts from the ignition switch. The RUN circuit runs through the ballast resistor which causes the power to drop. So there is 12 volts into the resistor but less coming out.

There is nothing in the ignition switch to change the voltage running through the switch. It's 12 volts in and 12 volts out. It's the ballast resistor that drops the power.

For more detail, when the key is in the START position power runs through a Brown wire to the resistor. At the resistor a Dark Blue wire should be attached with the Brown. Power runs through the Dark Blue wire to the coil, skipping the resistor. A full 12 volts from the switch to the coil.

In the RUN position, power runs through a Dark Blue wire to the resistor - opposite end of the resistor to where the Brown wire attaches. Power runs through the resistor and then via the Dark Blue wire to the coil. It's a full 12 volts to the resistor, but reduced power from the resistor to coil.

From the above you should understand why, when the ballast resistor dies, the engine will turn over and sound like it is running in START, but when you release the key and the ignition switch goes to the RUN position, everything dies.

A second Dark Blue wire is attached to the resistor with the Dark Blue wire for the RUN position which runs to the IGN connector on the Alternator Regulator. Has nothing to do with what we are talking about.

You are correct that there are no electrical components in the ignition switch to modify voltage, however, high resistance on the ignition contacts can cause a voltage drop as can high resistance in the bulkhead connector terminals. I am thinking that the hot lead to the ECU is wired to the wrong side of the resistor in this case as ECU's need full voltage to operate. Reduced voltage on some units is supplied to the coil via the resistor in the run position, but the power to the ECU should always be about 12.5 volts.

Dave
 
With the key in the START position there should be 12 volts from the ignition switch. The START circuit does not go through the ballast resistor. The system uses the full 12 volts to start the car.

With the key in the RUN or ON position there should be 12 volts from the ignition switch. The RUN circuit runs through the ballast resistor which causes the power to drop. So there is 12 volts into the resistor but less coming out.

There is nothing in the ignition switch to change the voltage running through the switch. It's 12 volts in and 12 volts out. It's the ballast resistor that drops the power.

For more detail, when the key is in the START position power runs through a Brown wire to the resistor. At the resistor a Dark Blue wire should be attached with the Brown. Power runs through the Dark Blue wire to the coil, skipping the resistor. A full 12 volts from the switch to the coil.

In the RUN position, power runs through a Dark Blue wire to the resistor - opposite end of the resistor to where the Brown wire attaches. Power runs through the resistor and then via the Dark Blue wire to the coil. It's a full 12 volts to the resistor, but reduced power from the resistor to coil.

From the above you should understand why, when the ballast resistor dies, the engine will turn over and sound like it is running in START, but when you release the key and the ignition switch goes to the RUN position, everything dies.

A second Dark Blue wire is attached to the resistor with the Dark Blue wire for the RUN position which runs to the IGN connector on the Alternator Regulator. Has nothing to do with what we are talking about.
All correct but the function of the ballast resistor is not really in question. From the OPs description, he has correctly wired his ECU to the RUN side of the BR, but he says that during cranking his ECU is not getting enough voltage to operate. He said he's using a Mancini ignition conversion kit, which is their version of the Mopar orange box kit.

Voltage drop through the resistor is proportional to the current draw (Ohm's law). I don't know how much current a Mopar ECU draws but it's probably not much, and the BR is only about 1-ohm when cold, so the Mopar ECU should run fine through the BR during cranking. If the battery voltage stays at 12V during cranking, the ECU draws 2A and the BR is 1-ohm, you should see 10V at the ECU tap point during cranking.) That's why we can connect it there, even though the RUN wire doesn't get power during cranking so the ECU gets its power through the BR instead.

If your multimeter is sensitive enough, you could directly measure the resistance of the BR to confirm. Set the meter to the lowest resistance setting. Touch the two probe leads together. If the measured resistance value is not zero, your meter has some internal resistance which will affect the reading. Subtract that value from what you measure when probing across the BR terminals to get a more accurate reading. Disconnect all wires from the BR and measure across the BR terminals. Should read around 1 - 1.5 ohms. If higher, that could be the problem, or at least part of the problem..

The OP did not state where he was putting the negative probe lead while measuring voltage at the BR wires. He also didn't state whether he had pulled the plug on the starter relay so the starter was not actually running during measurements. (I presume he did not.) These may affect the readings greatly.

Here is where I would continue diagnosis: First make sure your battery reads 12V with the key off. If not, attach a bench charger to charge it before continuing. (Don't test with the charger still connected. it will affect the measurements.)

Next you'll need a friend in the car to turn the key. Make sure loads such as heater blower and headlights are off. Pull the connector off the starter relay on the firewall so the starter does not run during START. Pull the leads off the BR and test them again in RUN and START positions. If the START lead measures low voltage with the key in START, suspect the ignition switch is bad. If you get close to full battery voltage, the ignition switch, bulkhead connector and related wiring are not the issue.

Reattach the connector to the starter relay. Disconnect the ECU so the car doesn't accidentally start during testing. While cranking check:
- voltage between battery + and - terminals. (Measure right on the battery posts, not on the connectors.
- voltage between battery + and the engine block. (The alternator case is usually a good place to find a solid connection.)
- voltage between battery + and the firewall, preferably on one of the screws that ground the ECU to the firewall.

If all of these measurements fall to 6~7V during cranking, I would suspect a bad battery. If the voltage to the block ground is significantly lower, suspect bad terminal connections on either cable or the negative battery cable from battery to block. If your negative cable is original it probably needs replacement. If only the voltage to the firewall ground is low, suspect the ground connection between block and firewall at the back of the right cylinder head, or the ground to the ECU itself.

If none of these are bad, we'd be back to suspecting the ignition switch or related wiring, but these should have been ruled-out already.
 
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All correct but the function of the ballast resistor is not really in question. From the OPs description, he has correctly wired his ECU to the RUN side of the BR, but he says that during cranking his ECU is not getting enough voltage to operate. He said he's using a Mancini ignition conversion kit, which is their version of the Mopar orange box kit.

Voltage drop through the resistor is proportional to the current draw (Ohm's law). I don't know how much current a Mopar ECU draws but it's probably not much, and the BR is only about 1-ohm when cold, so the Mopar ECU should run fine through the BR during cranking. If the battery voltage stays at 12V during cranking, the ECU draws 2A and the BR is 1-ohm, you should see 10V at the ECU tap point during cranking.) That's why we can connect it there, even though the RUN wire doesn't get power during cranking so the ECU gets its power through the BR instead.

If your multimeter is sensitive enough, you could directly measure the resistance of the BR to confirm. Set the meter to the lowest resistance setting. Touch the two probe leads together. If the measured resistance value is not zero, your meter has some internal resistance which will affect the reading. Subtract that value from what you measure when probing across the BR terminals to get a more accurate reading. Disconnect all wires from the BR and measure across the BR terminals. Should read around 1 - 1.5 ohms. If higher, that could be the problem, or at least part of the problem..

The OP did not state where he was putting the negative probe lead while measuring voltage at the BR wires. He also didn't state whether he had pulled the plug on the starter relay so the starter was not actually running during measurements. (I presume he did not.) These may affect the readings greatly.

Here is where I would continue diagnosis: First make sure your battery reads 12V with the key off. If not, attach a bench charger to charge it before continuing. (Don't test with the charger still connected. it will affect the measurements.)

Next you'll need a friend in the car to turn the key. Make sure loads such as heater blower and headlights are off. Pull the connector off the starter relay on the firewall so the starter does not run during START. Pull the leads off the BR and test them again in RUN and START positions. If the START lead measures low voltage with the key in START, suspect the ignition switch is bad. If you get close to full battery voltage, the ignition switch, bulkhead connector and related wiring are not the issue.

Reattach the connector to the starter relay. Disconnect the ECU so the car doesn't accidentally start during testing. While cranking check:
- voltage between battery + and - terminals. (Measure right on the battery posts, not on the connectors.
- voltage between battery + and the engine block. (The alternator case is usually a good place to find a solid connection.)
- voltage between battery + and the firewall, preferably on one of the screws that ground the ECU to the firewall.

If all of these measurements fall to 6~7V during cranking, I would suspect a bad battery. If the voltage to the block ground is significantly lower, suspect bad terminal connections on either cable or the negative battery cable from battery to block. If your negative cable is original it probably needs replacement. If only the voltage to the firewall ground is low, suspect the ground connection between block and firewall at the back of the right cylinder head, or the ground to the ECU itself.

If none of these are bad, we'd be back to suspecting the ignition switch or related wiring, but these should have been ruled-out already.
I'm reading your response correctly, the only point I'm going to disagree with you on is that the 4 pin ECU should be wired before the ballast resistor.

Example:

ecu3.jpg
 
I'm reading your response correctly, the only point I'm going to disagree with you on is that the 4 pin ECU should be wired before the ballast resistor.

Example:

View attachment 253807
We are not in disagreement. The ECU should be wired into the RUN side of the BR (blue wire). I wrote: "From the OPs description, he has correctly wired his ECU to the RUN side of the BR, but he says that during cranking his ECU is not getting enough voltage to operate."

The RUN wire is not powered from the ignition switch during cranking, only the START wire is powered. Therefore during cranking the ECU will be powered through the BR.
 
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