1963 Ballast Resistor Configuration

[Jack H.]

Re: 1963 Ballast Resistor Configuration

If you took the ballast off a '65-67 Chevy product in the scrap yard, then it's most likely that you wound up with a service spare part. If I recollect properly, Corvette was one of the last in Chevy's line to abandon the discrete ballast resistor and make the transition to the ballast resistor function being built into the wiring harness...

Further, the transition away from a discrete ballast resistor started WAY back in 1958-59...

Next, you'll find ballasts that are similar to what we see used on Corvette but with subtle differences. Like: the 'bump' along the outside back edge of the mounting tab and/or a flared collar surrounding the back side of the bolt hole in the tab. These differences stem from different mounting techniques used by other GM car lines.

The 'bump' was a protective measure to thwart the ballast from 'spinning' on its mounting bolt relative to an intended position. Such movement, depending on where the ballast was physically mounted might let the attaching wires physically touch an adjacent metal surface and short out the ignition...

The same is true of the version of the ballast that has a 'collar' protruding from the back side of the mounting hole. The collar mated with a recess in the target vehicle's mounting hole and kept the ballast shifting up/down or side to side.

Chevy was one of the few car lines that mounted the ballast on the underhood body panel. Others typically attached the ballast to nearby engine components (e.g. coil mounting bracket)...

[Jack H.]

Re: 1963 Ballast Resistor Configuration

See my reply to Chuck above. Then, if you want to see ballast resistors with 'back of the mounting tab' protrusions, go look at older Pontiac, Buick and Cadillacs the next time you're yarding.

Oh, PS, don't bother looking at those cars if their engines are gone...the ballast went with the engine!

[Jack H.]

Re: 1963 Ballast Resistor Configuration

In addition to the screws being tight, you're measuring a resistance that SO SMALL now that the intrinsic probe resistance of your meter AND the ohmic contact profile of your probes (how tight/hard are you pressing?) both become significant to the reading!!!

The BW to measure/verify this level of resistance is to CALCULATE it. By that I mean connect the ballast to a self-regulating voltage source (like a triple output lab bench supply) and measure the steady state DC current that flows. Now, calculate R (R= V/I) making sure that your voltage source didn't 'droop' and your measured current was steady state STABLE.

[Jack H.]

Re: 1963 Ballast Resistor Configuration

It's truly a rare day when Mr. Mike hath mis-spoken!!!

[Wayne M.]

Re: 1963 Ballast Resistor Configuration

.....connect the ballast to a self-regulating voltage source (like a triple output lab bench supply) and measure the steady state DC current that flows. Now, calculate R (R= V/I) making sure that your voltage source didn't 'droop' and your measured current was steady state STABLE.

Jack -- were the conventional ohm values for our favorite car (1.8 blue stripe; 0.4 for the black dot) at rated operating temperature [ie. not cold, on the bench] ? And would this op temp vary with engine speed ?

[Dan D.]

Re: 1963 Ballast Resistor Configuration

In addition to the screws being tight, you're measuring a resistance that SO SMALL now that the intrinsic probe resistance of your meter AND the ohmic contact profile of your probes (how tight/hard are you pressing?) both become significant to the reading!!!

The BW to measure/verify this level of resistance is to CALCULATE it. By that I mean connect the ballast to a self-regulating voltage source (like a triple output lab bench supply) and measure the steady state DC current that flows. Now, calculate R (R= V/I) making sure that your voltage source didn't 'droop' and your measured current was steady state STABLE.

Beware of corrosion when trying to get accurate measurements of ohmic value. Old resistors, such as the one Wayne posted, are for sure badly corroded and it doesn't take much when you are trying to measure tenths of an ohm. In particular, the resistance wire is crimped to a lug and then squeezed under the nut by the screw. I measured several ballasts awhile back, and mechanically removed all the crud and then soldered the crimp lug to the nut in order to get a true '0' resistance at this juncture. Noticeable resistance difference when doing this.
Using a power supply, load resistor and ohms law as Jack suggests is a very good way to calculate actual resistance. If you have a meter with an accurate low ohm scale you can get good accuracy by using probes with sharp points that will 'punch' through surface contamination, and then subtracting out lead resistance. -Dan-

[John M.]

Re: 1963 Ballast Resistor Configuration

The best way I know of to clean a ballast resistor is in a heated ultra sonic machine with dish / hand soap and water.....Thanks JOHN

[Jack H.]

Re: 1963 Ballast Resistor Configuration

The drawing does not specify a specific test setup for measuring resistance. It simply states 0.30-0.38 ohms.

Wire wound resistors are pretty stable critters, but you can expect resistance to change as a function of temperature.

[Jack H.]

Re: 1963 Ballast Resistor Configuration

Yes, the surface oxidation you mention at different places throughout the resistor (nichrome wire with crimped terminal, crimped terminal pinched to ceramic screw terminal insert(s), screw terminal to mounting washer) DOES have an impact. And, that impact will vary with component temperature, driving voltage and current flow.

Most multimeters use a small 1.5V battery to supply the circuit under test probe current for resistance measurements. That's why I suggest using a self-regulating 12 VDC power supply, measuring actual steady state current flow and calculating the resistance based on actual current flow.

But, expect to 'cook' the ballast if you don't add addititional series resistance with this approach! If the actual resistance is 0.3 ohms and you hit the ballast with a 12V supply, that's going to flow something like 40 amps of current!

So, you can improve the test setup by putting the ballast in series with a couple of light bulbs (e.g. 1157 filaments). Now, measure the circuit that flows and flip the meter back to voltage mode and jot down how much voltage is being dropped across the ballast resistor before you make that resistance calculation.

This way you're driving the ballast with a voltage that's in the range of its normal operation and you're drawing enough current to minimize the oxidation effects at various ohmic contact points...

[Jack H.]

Re: 1963 Ballast Resistor Configuration

I've tried various methods and have to admit there's NO really good way to make that aged, pitted, ceramic surface gleam like new...

Do NOT try to media blast it as that will open surface cracks galore!

Soft and gentle approaches come out about as good as you can expect (use Comet scouring powder and a tooth brush, use a denture cleaning agent + soft scrubbing).

[Chuck G.]

Re: 1963 Ballast Resistor Configuration

I think you'll find the ballast with the deeply etched "0.2 OHMS" legend on the ceramic is the current reproduction part. Factory (and service) original ballasts were NOT labeled in this fashion...

Yep, one repro I have, the one with the 0.2 OHM etching is/was from my 409 buddy. Not sure where he bought it.

The other from the Corvette supplier has no etching. It's 0.3 OHM.

BUT......................... I keep bringing this up.............

We have about 26 posts and over 400 views in this thread, and still no answer to my question about the length of the tab.....

For 63, should the tab be the shorter 1/4" example or the longer 7/16" example?

Does anybody REALLY know for sure? Were both styles used in 63?

Chuck

[Jack H.]

Re: 1963 Ballast Resistor Configuration

Let me repeat myself from the 4th entry in this thread, Chuck.

"As to the shape of the mounting tab (whether it's gently rounded or more squared; your LH vs. RH picture), the general consensus is existing tooling from the era produced BOTH versions. It's the presence/absense of the tear-away tab on the end/center of the rounded portion of the tab that is looked for."

The bottom line is most senior judges know different tooling existed to create the ballast bands and BOTH versions of the resistor show up. I think we know we don't know when the alternate tooling first surfaced and judges going back into the late C1 era accept either version of the band.

BUT, it's the presense/absence of the tear-away tab that's looked for on both versions of the band until you get to the '66-68 era. Last, this ruling is, of course, based on the specific knowledge of the particular judges you pull at a given meet...

[Chuck G.]

Re: 1963 Ballast Resistor Configuration

BUT, it's the presense/absence of the tear-away tab that's looked for on both versions of the band until you get to the '66-68 era. Last, this ruling is, of course, based on the specific knowledge of the particular judges you pull at a given meet...

Yep, I saw that in post #4, and thus I must assume that there is no clean "break point" between the more square version with the 7/16" break-away tab and the more rounded version with the 1/4" break-away tab in the 1963 time frame.


Chuck

[Jack H.]

Re: 1963 Ballast Resistor Configuration

If you assume that, you've walked away with what I believe to be the correct picture, amigo!

[Ray C.]

Re: 1963 Ballast Resistor Configuration

Chuck!
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I had a June 63 SWC car and the resistor had the small tang like you would expect to find on a C-1. The ceramic was cracked and I had to replace it. I can not confirm that it was original to the car, but almost everything on this 63 was original.

Ray