Hi guys this bit of info hopefully will keep someone from pulling their hair out .
Quote from Hemmings Motor News
"General Motors vehicles used the same 6-volt non-resistor ignition coil from 1923-'54. When they converted to 12-volt in 1955, the coils were 12-volt and externally resisted. The same coil was used from 1955 right up until 1975; however, a resistance unit was required on GM vehicles newer than 1963. General Motors changed to their "coil in the cap" (HEI)electronic ignition in 1975."
resistance unit = a resistance wire
Fords also used a pink resistance wire also,2 Quotes from a vintage Mustang forum
"The 1965-73 Mustang ignition systems did not install ignition coils that had an internal resistance built into them. Resistance is required somewhere in the ignition wiring between the keyed 12V power source and the coil to prevent a variety of bad things from happening (coil and points damage, tachometer damage, wire overheating). As such, Ford installed this resistance into the wire itself that goes from the switched ignition source to the coil’s positive terminal. This is a very hard and heat resistant tungsten wire (pink color on the 1970s"
" THIS CALIBRATED RESISTANCE WIRE IS 1.5 OHMS. THE BALLAST RESISTANCE WIRE IS MADE OF TUNGSTEN TO WITH STAND HEAT. NEVER CUT THIS WIRE AS IT CAN'T BE RESTORED IN ANY WAY!"
(Not sure how many OHMS the Chevy wire is)
I'm working on a 1972 Chevy truck and it has a resistance wire which on this truck and it is pink .I think other colors also might have been used for resistance wire to the coil .
If your working on a Chevy truck or car and it has this small pink wire in the engine bay ,this most of the time will be the hot wire from the ignition switch to the coil . The resistance wire if you clean it up you will see the words "resistance wire do not cut" written on it.So if you are putting a later model harness in your truck or car or working on a later model truck or car keep this in mind it will not support electronic ignition or any thing else that needs a full 12 volts .If you connect a test light to it ,it will burn very dim .
But it will trigger a 12 volt relay .
I will never forget how much trouble this wire gave me once before .
Last edited by PAUL NOLZ; 02/22/2015 4:27 AM.
