Looking for ohms rating of this pink wire to replace it on 69 xr7. Mine has melted the insulation off of it(Not sure why yet). I have a wire spliced into red/green tracer on back of ign switch running to the trigger on a relay to power a small aux fuse panel that powers my pertroniix and sniper switched 12v. Also, how would i splice a new one in since it goes through firewall and into a 4 wire connector? Or could i replace it with a ballast resistor block and regular wire? Thanks!
If you install a coil with less resistance then the stock coil it smokes the resistance wire. You could use a Mopar resistor under the hood instead. The factory tach depends on a certain amount of current to operate correctly so if you change anything then it won’t be accurate.
I measured one years ago and it was around 7 Ohms, same as a Mopar ceramic resistor.
Thanks. Using stock 3ohm coil with ignitor II setup. I think i saw 6 ohms posted somewhere in my research, but of course can’t find it again lol. Part store Listings don’t give ohm ratings on websites for the blocks. Only saw msd list as .8 ohm…too low tho
The 1969 shop manual specs the primary resistance wire as 1.3 - 1.4 ohms.
The MOPAR dual ballast has a 1.5 ohm side and a 5.0 side. The single style ballast resistor should be 1.5 ohms.
Too much resistance will make the tach read low, lower resistance will make it read high.
+1. The pink resistor wire is supposed to be 1.3 to 1.7 ohms nominal. When current flows through it, it heats up, raising the resistance, which lowers the current. It’s a neat trick for a current-limiting device!
You can’t measure voltage across a resistance with no current flowing through the circuit. And some resistive loads are reactive. Meanings you must test circuits under load. This is something you have to know because you can’t see it
That was a Gotcha Question on interviews for Electronics Tech Jobs back when it mattered if you understood Ohm’s Law.
Mike M.
You actually can measure resistance accurately and apply ohms law in electronics where there is negligible heating in the resistor. But no, definitely won’t work on resistance wires.