An embarrassing question

[Harry S.]

I hate to even post this but I am stumped.

When I put the OHM meter on my C6 spark plug wires I can see the resistance and calculate if they are good or bad.

I have a set of 4 Q 62 wire on my 63. When I perform the same test I get no results. It's as if the wire has a break, but the car runs. Saying that, I have a 6 inch piece from the same 100 foot spool of unused wire. Same reaction, no resistance.

How does one bench test these?

What am I missing?

[Mark E.]

Re: An embarrassing question

"has a break" is different than "no resistance".

Are you measuring infinite resistance or zero resistance?

[David H.]

Re: An embarrassing question

Harry

Carbon core or wire core?

Dave

[Harry S.]

Re: An embarrassing question

Harry

Carbon core or wire core?

Dave

Carbon core, this is 58 year old NOS Delco wire

[Joe R.]

Re: An embarrassing question

Harry,

When Carbon Core is broken and has little or no resistance it can still work well cause the spark will jump the break! Just like it does on the spark plug! It will eventually burn a hole in the insulation and quit working!

JR

[Larry M.]

Re: An embarrassing question

Agree..............carbon core wire does not last forever. Typically 10-20 years was its service life.

Time for new wires.

Larry

[Harry S.]

Re: An embarrassing question

Let me ask the question again. These are new wires made from NOS 4 Q 62 wire. How are they tested. They have not been installed yet.

[Gary C.]

Re: An embarrassing question

Harry,

Do you have a good digital VOM? IIRC carbon wires resistance can run anywhere from 4k ohm to 12k ohm resistance. The better the wires the lower the resistance.

Gary
....

[Larry M.]

Re: An embarrassing question

Things like carbon core wires can deteriorate on the shelf. Test as Gary says, and if you used a good meter and got very very high resistance or an open circuit, you have your answer.

Larry

[Frank D.]

Re: An embarrassing question

Personally, if that style wire is that old, I'd think twice about installing them...but its not my car.

[Harry S.]

Re: An embarrassing question

Personally, if that style wire is that old, I'd think twice about installing them...but its not my car.

Before I bought the 100 ft spool I did a good deal of research. Essentially the conclusion was that the carbon wire will last forever. After installed and put in service many things can go wrong. Scrapes, pinching, burns, etc.

I built two sets, one set is in my 300hp coupe and the other was in the 250hp convertible. The coupe has been running great for years. I shot the parts cannon at the convertible to fix a problem. I installed the Summit wires there. I'm just trying to test them to see if they failed. I'm trying to compare the resistance against a third set I just built.

[Frank D.]

Re: An embarrassing question

Before I bought the 100 ft spool I did a good deal of research. Essentially the conclusion was that the carbon wire will last forever. After installed and put in service many things can go wrong. Scrapes, pinching, burns, etc.

I built two sets, one set is in my 300hp coupe and the other was in the 250hp convertible. The coupe has been running great for years. I shot the parts cannon at the convertible to fix a problem. I installed the Summit wires there. I'm just trying to test them to see if they failed. I'm trying to compare the resistance against a third set I just built.

"Parts cannon" - Nice!

I just did a spark plug and wire install on my 250hp week before last, snaking the wires through the motor mounts and looms and wrestling with the shielding - a PITA. Would have been brutal without a lift... To wit, if you can make 100% certain the wires will be good when done then I guess its OK...

[Harry S.]

Re: An embarrassing question

"Parts cannon" - Nice!

I just did a spark plug and wire install on my 250hp week before last, snaking the wires through the motor mounts and looms and wrestling with the shielding - a PITA. Would have been brutal without a lift... To wit, if you can make 100% certain the wires will be good when done then I guess its OK...

I got that from you... I like it also!

[Joe R.]

Re: An embarrassing question

Before I bought the 100 ft spool I did a good deal of research. Essentially the conclusion was that the carbon wire will last forever. After installed and put in service many things can go wrong. Scrapes, pinching, burns, etc.

I built two sets, one set is in my 300hp coupe and the other was in the 250hp convertible. The coupe has been running great for years. I shot the parts cannon at the convertible to fix a problem. I installed the Summit wires there. I'm just trying to test them to see if they failed. I'm trying to compare the resistance against a third set I just built.

Hi Harry:

Tell us more about the ohm meter you are using. A hand-held ohm meter applies, at most, a few volts to measure resistance. It is possible that the resistance measured with a few volts is higher than the resistance measured with 30,000 volts from the coil.

Another factor is when the ohm meter has selectable ranges rather than auto-range. If the meter range is set to 10K ohms, any resistance larger than 10K ohms will read as "infinite."

If the ohm meter range is set to meg-ohms (millions of ohms) and it still measures "infinite," it is possible that the carbon-composition cable has a tiny open circuit that won't break down at 5 volts but will break down at 30,000 volts. However, I think that a carbon-composition cable that behaves this way is in the process of failing open, even at 30,000 volts. I believe that healthy carbon-composition wires measure at a few hundred ohms per foot when tested using an ordinary ohm meter.