[malstrom]

Hi firends

I recently looked at the ballast on my long sitting all OEM 289 66 . The old ballast connector were loose so i replaced the unit and get lower results. I have a Blaster 2 MSD coil and old school points. Nuthin in my car is modified./.
Here was my prior readings with old ballast .


Okay here's what I get at the engine compartment. I lean over the engine, with my meter test leads . first ballast connection closest to firewall ( wire from firewall is red ) then connected to block I get 11.1 volts. Both leads to each ballast connector 7.77 volts. Ballast connector closest to radiator ( call it front ballast point ) and then lead to block/ground 3.5 volts . "front ballast point' to "+" connector new coil .75 volts. front ballast point to "-" on new coil 3.0 volts . and i drive this car just fine.

So i installed the new MSD recommended 1426 model resistor .8 ohm resistance with my MSD coil. . I get 12 volt from the fore wall 5.5 volts across the ballast leads and 5.5 volts onward tot he coil POSITVE terminal.

Did I purchase the wrong ballast . Is the voltage to low? should it not be 7-9 volts onward to the coil.?

The wire from the firewall seems not to be a resistance type wire, but what do I know.

The ( call it front ballast point ) contain two black wires one going to the coil the other go to rear of engine probably to solenoid.

 

[awhtx]

If you have a ceramic resistor you don't have an "all OEM 289 66", "nuthin in my car is modified". The factory resistor was the infamous "Pink Wire" which is all under the dash inside the car. If your Pink Wire is still intact you don't need any ceramic resistor.

 

[malstrom]

If you have a ceramic resistor you don't have an "all OEM 289 66", "nuthin in my car is modified". The factory resistor was the infamous "Pink Wire" which is all under the dash inside the car. If your Pink Wire is still intact you don't need any ceramic resistor.

Good to know. I have a RED wire as I explained earlier from the firewall. I though the PINK wire passed thru the firewall. Getting lost somewhere in my electrical wrap. If Indeed I am measuring the voltage at 11.1 volts to the resistor Ballast. The Pink or Red color is irrelevant? Would 12 volts directly to a Old school coil and points be damaging? what is the consensus?

 

[oscarnielsen]

Good to know. I have a RED wire as I explained earlier from the firewall. I though the PINK wire passed thru the firewall. Getting lost somewhere in my electrical wrap. If Indeed I am measuring the voltage at 11.1 volts to the resistor Ballast. The Pink or Red color is irrelevant? Would 12 volts directly to a Old school coil and points be damaging? what is the consensus?

The points will burn out faster and your coil will run hotter. However, if you like filing/gapping points on a regular bases you're OK. My friend runs his 66 mustang that way. He carries extra points/condenser and coil in the trunk. He has never had to use them "LET"

 

[carlite65]

If you have a ceramic resistor you don't have an "all OEM 289 66", "nuthin in my car is modified". The factory resistor was the infamous "Pink Wire" which is all under the dash inside the car. If your Pink Wire is still intact you don't need any ceramic resistor.

the pinkwire resistance is encased in a wrap under the dash. it comes out of the firewall thru the plug. the engine side is not resistance wire,

 

[awhtx]

The high resistance pink wire (16A) ends at the interior side of the firewall electrical connector. The low resistance red/green wire (16) begins on the engine side of the firewall connector.

http://averagejoerestoration.com/resources/mustang-wiring-and-vacuum-diagrams/1966-wiring-diagrams/66ignit.jpg

If you have a red wire coming out of the firewall connector it is possible that a PO removed the male and female bullets from the rubber connector halves and ran a red wire from the ignition switch to the coil, passing through the now empty holes in the connectors.

 

[malstrom]

The high resistance pink wire (16A) ends at the interior side of the firewall electrical connector. The low resistance red/green wire (16) begins on the engine side of the firewall connector.

http://averagejoerestoration.com/resources/mustang-wiring-and-vacuum-diagrams/1966-wiring-diagrams/66ignit.jpg

If you have a red wire coming out of the firewall connector it is possible that a PO removed the male and female bullets from the rubber connector halves and ran a red wire from the ignition switch to the coil, passing through the now empty holes in the connectors.

Thanks awhtx and also Thanks Carlite65

You guys are swell, As i rip open the electrical wire wrap and trace the red wire in the engine compartment. That exactly what happens. the wire meets a simple plastic Barrel connector to make a "butt joint" and still inside the compartment . Then continues red to a 1/4 inch hole in the firewall just under the hood hinge. I track that thru to what looks strongly like a heading right to the ignition switch and its stuck fast without my trying to take out the switch.

Strange now that you have edumatated me I also find that heavy thick pink insulation wire wrapped up and with its cut end dangling proud.

So the diagnosis is ......what do you guys recommend . Take out the ballast and run straight to the coil. ?


I'm not a guy who can diagnosis a in field petronix failure. So I will always be a points guy. I 've been planning for parts and tools in the trunk. what kind of life span do you think points might have? 2000 miles before "Houston we have a problem" .?

 

[awhtx]

"So i installed the new MSD recommended 1426 model resistor .8 ohm resistance with my MSD coil."
Since you say you installed the resistor recommended by MSD you shouldn't need to do anything else. Unless they recommend that resistor in addition to the factory pink wire. What do the instructions say? We recently went through a lengthy discussion about Pertronix's instructions regarding resistance in the coil circuit.

 

[Huskinhano]

When measuring voltage you need to be aware as to how the meter is connected. Otherwise you'll get voltage readings that don't make sense. In Ohm's series laws what ever has the highest resistance drops the most voltage. Volt meters have very high resistance. So if you have your resistor wire disconnected from the coil, you're going to read the full battery voltage. Or if the wire is still connected and the points are open you'll still read full battery voltage. Now with the wire connected and the points closed and you put the volt meter across each terminal of a ballast resistor or at each end of the resistor wire and the same goes with the coil, on each terminal of the coil you are now connecting the volt meter in parallel instead of in series, you are now reading voltage drop of each device or in your case the resistor wire and coil at 5.5 volts it may very well be correct. It means both have the same resistance and both are dropping 5.5 volts which adds up to 11 volts. Your battery voltage will probably be around 12.5 volts. Add in voltage loss or drop on the factory wiring harness would be right around that 1.5 or more voltage loss.

 

[Woodchuck]

One of the other fine points of the original resistance wire is the fact that it was installed on the switch "side" of the splice with the brown "bypass" wire from the starter solenoid "I" post so that the coil would receive "unresisted" voltage when the engine was cranking, making starting easier. FWIW, measuring resistance in an open circuit (points not touching) with a digital multimeter will commonly produce a false reading as the meter lacks the internal resistance to properly measure the circuit voltage. Probably easier to measure ohms through the ignition switch to see the entire circuit resistance from battery + to coil -.

 

[Huskinhano]

FWIW, measuring resistance in an open circuit (points not touching) with a digital multimeter will commonly produce a false reading as the meter lacks the internal resistance to properly measure the circuit voltage. Probably easier to measure ohms through the ignition switch to see the entire circuit resistance from battery + to coil -.

Actually a digital VOM is going to have a much greater internal resistance then the old analog meters with 20-25K ohms per volt. The digital will have less meter loading. Back in the day many cheap analog meters would be around 10k ohms per volt and would effect readings. The most important thing is to understand how the meter is connected to a circuit and have a idea of what voltage you are looking for.

 

[malstrom]

So confusion remains for me. I put the daily driver battery back in the mustang and found from the Battery + post to the rear of the Ballast resistor and I have 12.4 V with the key in the"on"position.

But I cannot trace anything else thru the line to the coil and get readings ! Just Zero.

If I measure the front post on the Ballast to the Engine ground. I get 12.4. But from front ballast post zero to the coil pos and neg posts. just zero.


I try to measure with car running the meter just rolls the number on my cheap Harbor Freight tools meter. Earlier I was thinking of just dropping the ballast completely . Now I dont understand ...... The car cranks and starts normally .

 

[Huskinhano]

So confusion remains for me. I put the daily driver battery back in the mustang and found from the Battery + post to the rear of the Ballast resistor and I have 12.4 V with the key in the"on"position.

But I cannot trace anything else thru the line to the coil and get readings ! Just Zero.

If I measure the front post on the Ballast to the Engine ground. I get 12.4. But from front ballast post zero to the coil pos and neg posts. just zero.


I try to measure with car running the meter just rolls the number on my cheap Harbor Freight tools meter. Earlier I was thinking of just dropping the ballast completely . Now I dont understand ...... The car cranks and starts normally .

Your points are open that's why.

 

[dennis g]

About meter readings, analog ohm meters adjust to zero with a variable resistor and they come quickly to a reading. I like them for that.

digital meters hunt around for a while before finding a final reading but they still may not measure low ohm readings well so they
1. must have a good (new) battery and
2 they probably still will be off an ohm or more. so pull a meter out of the Harbor Freight meter box and use a one which is off an easy number to subtract ( 1 ohm error is easy)
only then can you get a reading good enough for your ignition system.
3 they can be precise, but precision and accuracy are not the same. I prefer accuracy every time, it means more.



Don't try to measure resistance on a live circuit. Disconnect the component and then test it. You will not fry your meter that way.
afterthought: I loaned a good friend a expensive meter, he returned it and another both partially blown out. I said nothing. Loan your friends free Harbor freight meters only. If they don't have one, it is probably because they don't know how to use them.

 

[Woodchuck]

About meter readings, analog ohm meters adjust to zero with a variable resistor and they come quickly to a reading. I like them for that.

digital meters hunt around for a while before finding a final reading but they still may not measure low ohm readings well so they
1. must have a good (new) battery and
2 they probably still will be off an ohm or more. so pull a meter out of the Harbor Freight meter box and use a one which is off an easy number to subtract ( 1 ohm error is easy)
only then can you get a reading good enough for your ignition system.
3 they can be precise, but precision and accuracy are not the same. I prefer accuracy every time, it means more.



Don't try to measure resistance on a live circuit. Disconnect the component and then test it. You will not fry your meter that way.
afterthought: I loaned a good friend a expensive meter, he returned it and another both partially blown out. I said nothing. Loan your friends free Harbor freight meters only. If they don't have one, it is probably because they don't know how to use them.

^ ^ ^ This. If you're going to try and measure the resistance on a live circuit use "voltage drop" instead.

 

[GT350HR]

If you run an MSD , you don't need any ballast resistor , even if you are using the points as a trigger.

 

[dennis g]

^ ^ ^ This. If you're going to try and measure the resistance on a live circuit use "voltage drop" instead.

You are absolutely right. Measuring voltage drop is the way to go. It does not destroy your meter, even cheap digital meters can do it well and a brand new battery is not required as the circuit measured powers the meter.

 

[GT289]

Determining the correct resistance value to have the right volts arrive at the coil is a PITA for most folks.
I just went through this on my 70 year old Ford flathead truck. Previous owner had slapped on a generic "Chrysler"
ceramic ballast resister. Difficult cold starting and crap for gas mileage was the norm. Didn't bother breaking out the
meter, merely replaced the generic item with a Standard Motor Products RU-10 resistor. (the correct item for my application)
Starts on the first turn of the key and it's 40 degrees in the morning right now. Mileage appears better as well.

 

[dennis g]

the coil and resistor for your flathead truck did not work together but you corrected that by putting the proper ballast in and it worked better as would be expected.

Coils with internal ballasts are made for individuals who can not get things right. If it fails, both coil and ballast are replaced as a unit.

Coils for external ballasts give the option of making a mistake or not and the advantages of allowing adjustment of coil voltage and also only having to replace the part that burns out.

It is like selling sealed, disposable flashlights for those who put some of the bateries in backward .

 

[rpm]

what kind of life span do you think points might have? 2000 miles before "Houston we have a problem" .?

You should get at least 10k miles from a set of points. I know I do.