61 Corvair Rampside Resistor help

[bsodt]

I have read many post etc and not sure how mine relates to most. My 61 did not have a ballast resistor when i bought it but i was told i needed to get one. So i bought one from NAPA yesterday and installed. It seems that the ballast has 12.1 volts on both sides of the resistor. So even after installing the resistor it is still getting the full 12 volts to the coil and to the points.

Any help is appreciated, every where i touch its always 12 volts. All i did was cut the wire and insert the brand new resistor. Am i crazy or just not understand the videos on you tube that clearly show the resistor reducing current.

Thanks
Bill

[Jerry Whitt]

A resistor does not cut voltage (pressure) but does cut down on the flow or amperage, The basic idea is that the points, when in a closed position, allow amperage flow thru the coil. As the points open and close, arcing happens at the points. This arching causes point wear and damage. By installing a resistor, the actual flow (amperage) is reduced, their by adding longer life to the points.

Your Rampy probably had a resistor wire in the system. Usually the wire is covered with a white fabric.

[bsodt]

I found a pretty good post and I have deducted this:

When the points are closed, I am getting 5.3 volts to the coil without the resistor. With the resistor inline i only get 3.3 volts with the points closed so that shows me how the resistor works. So i must not need the after market resistor as it is inline some where already.

With the points open I get 12 volts everywhere and as I read that is all correct, 12 volts open 6-8 volts closed.

My concern now is I am only getting 5.3 volts to the coil at all times with the points open. Is 5.3 volts enough to run the engine properly? I am getting some "engine missing" at 3/4 to full throttle could low voltage to teh coil be suspect?

Thanks
Bill

[Jerry Whitt]

The charging system is designed to produce about 14 volts. Around half of that is an acceptable range.

[66vairguy]

Bill - As you discovered, the ballast resistor does indeed drop voltage to a lower value, but ONLY when amperage flows. The "ballast" or resistor wire on most old GM vehicles is a long resistance wire in the engine wiring harness. It sounds like you are getting the proper values with the engine off and points open or closed. Keep in mind that battery voltage is about 12.8VDC (lower than 12.5VDC and the battery is running down) and when you have the engine running the generator/alternator voltage will be 13.5-14.5VDC.

Suddenly you have about 5.3VDC at the coil (I assume the "+" terminal) with the points open. First remove the wire at the "-" coil terminal and check the coil "+" terminal. If it rises to about 12.5VDC then the points are NOT open, or the wire from the coil "-" terminal to the points is shorted to ground (case of distributor) or the points are shorted to ground.

[toytron]

Yes in an electrical circuit when measuring an open circuit (points open) you will ideally measure open circuit or full voltage. With the points closed and measuring across the resistor you will read the voltage drop created by the addition of that resistor. If you subtract that voltage drop that you measured across that resistor from your circuit voltage you will have the voltage that the rest of the circuit is getting. Remember in a series circuit current is the constant. By adding the resistance in series you change the total current flowing through the circuit. If you knew the total current you could multiply that by your resistor value and then come up with your voltage drop across the resistor also. So that being said, in a series circuit with current being the constant voltage is different across each device in the loop. I hope I didn't confuse things.

Ed Stevenson

[bbodie52]

The first diagram below is from pages 8-26 and 8-27 of the attached 1961 Corvair Shop Manual - Section 8, Electrical Systems. The wiring diagram shows the resistor wire, and the chart shows the expected voltage ranges that should be found with the points open and the points closed. Your Corvair may very well have a resistor wire already in the circuit that you were unaware of. You can bypass the factory wiring temporarily by disconnecting the wiring harness feed from the added external resistor. Connect it directly to the wire on the other side, so that power is fed to the coil without passing through the resistor you added. With the key on and the points closed, you should measure 4½ - 6½ VDC, as described in step 5 of the chart. If there is no resistor wire in the circuit, you will read a much higher voltage. (The voltage you seem to be reading now with the points closed is too low, which may indicate that you have added a second resistor to a circuit that already has a resistor wire in the circuit).

The 5.3 volts you mentioned without the added resistor, and with the points closed is within the 4½ - 6½ VDC range shown in the chart in section 5. This seems to indicate the presence of a resistor wire in the factory harness. In this case you would want to remove the added resistor.

The factory harness is wired to provide a full battery voltage (Nominal 12 VDC) to the coil whenever the starter solenoid is energized (cranking the engine to start it). This higher voltage provides a "hotter" spark from the coil, to make it easier to start a cold engine that is being cranked. However, this higher voltage also increases the operating temperature of the ignition coil, and causes excessive arcing and burning of the ignition points contacts. Engineers determined that a lower voltage (nominal 6-7 VDC) would be adequate for normal engine operation, and would reduce coil heat buildup and would extend the life of the ignition points between tune-ups. When the engine starts and the operator releases the key, the starter solenoid disengages and the higher voltage feed to the coil is discontinued. This leaves only the voltage feed from the ignition switch, through the resistor wire, to the coil -- which is optimum for a running Corvair engine.

Left-click each diagram with your mouse to enlarge for better viewing...

The diagrams below are improved diagrams extracted from the 1962 Shop Manual Supplement. These diagrams were much-improved over the original diagrams Chevrolet used in 1961, which are somewhat confusing and appear to be developmental engineering diagrams, as opposed to the redrawn schematic diagrams found in 1962-1969 Corvair shop manuals.

1962 Combined Passenger Compartment & Engine Compartment Wiring Diagram

1962 Corvair 95 Full Schematic

1962 Corvair Engine Compartment Wiring Diagram