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No spark after a few seconds and Ballast Resistor specs
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Author:  GuyLR [ Wed Apr 23, 2003 4:31 pm ]
Post subject:  No spark after a few seconds and Ballast Resistor specs
Thanks to the ignition diagrams on the site I was able to narrow down the cause of the ignition going sparkless on my '65 Bcuda. It would shut down after a few seconds or minutes. It started about 6 months ago and the time to shutdown kept decreasing to where she wouldn't start at all. I converted to electronic years ago with an Orange box and MP distributor. The diagrams showed me which wires to check and it came down to an out of spec dual ballast resistor with 0.55 ohms (close) and 1.5 ohms (too high) or maybe a bad box. I ordered a new orange box from Summit Racing ($37.99+7.95SH) and bingo that was it. My question is, is the 1.5ohm reading on one side of the resistor too high?
Author:  Pierre [ Thu Apr 24, 2003 12:57 am ]
Post subject: 
Make sure when you are measuring the resistor that nothing is hooked up to it. And from what I see on the diagram, the dual ballast should be 0.5 and 5 ohms.. so 1.5 would sound too low. I am not infront of my car now but I can measure my resistor when I am.
Author:  dgc333 [ Thu Apr 24, 2003 5:57 am ]
Post subject: 
If you have an orange box ECU you do not need the dual ballast resistor. The high resistance side of the ballast resistor is not hooked to anything. Only 4 wires connect to the Orange ECU (and all after market replacement ECU's for that matter), power, (2) to the distributor pickup and the negative side of the coil. They left the fifth pin location on the ECU connector so that they would be a drop in replacement for the early factory 5 pin design.

I would not get too hung up on the value of the other side of the ballast resistor. As long as it's within .2 ohms or so it's not going to have an impact. The purpose of the resistor is to limit current flow through the coil at low rpm's so the coil does not over heat. It does this by the fact that the resistance of the ballast resistor will increase as it gets hotter from the addtional current drawn by the coil at low rpm's.

FYI, the orange, chrome and gold mopar ECU's do not do anything to improve the ignition output, they were designed to support the higher rpm range of modified motors. The orange box is rated to 6000 rpm on an 8 cylinder motor. Since a slant 6 only fires the ignition 3/4 as often as an 8, the orange ECU will support 8000 rpm on a slant. The stock ECU is plenty good for any slant operating up to 6000 rpm.
Author:  GuyLR [ Thu Apr 24, 2003 4:19 pm ]
Post subject: 
Thanks for the info. I mis-typed the high side resistance on my first post. It should have read 5.5 ohms and 1.5 ohms. The Chrome box diagram shows the Compensating resistor at 1.2ohms so I'm close with 1.5. If the high side auxiliary isn't used I should be able to just wire it like the Chrome box diagram and use one of my old point system resistors. Am I right in thinking it will not hurt an Orange box? Or is the lower resistance going to pass too much current to it? By the way Chuck's note on the basic electronic diagram (black box) says that it's compensating resistor is only 0.5ohms instead of 5.0.
Author:  Chuck [ Sun Apr 27, 2003 12:08 am ]
Post subject: 
I made that note because I couldn't edit the wiring diagram, as it is a graphhic file. Unfortunately I don't know about the orange boxes. I suspect that the wiring instructions would say what the resistance of the resistor should be, but just guessing.
Author:  dgc333 [ Sun Apr 27, 2003 4:58 pm ]
Post subject: 
Mopar switched to the single resistor electronic ignition that is shown in the second diagram http://slantsix.org/articles/elect_ign_ ... wiring.htm on this page in the late 70's.

From that point on all years of mopar replacement ecu's didn't use the compensating resistor either (it is a direct drop in replacement for the 5-wire ecu). Maybe some of the very early Mopar Performance ecu's (Orange, Chrome or Gold) used the compensating resistor but anything you may have purchased since 1980 would only have have 4 connections and does not need the dual ballast resistor. Also, anything you may get from the after market does not use the dual ballast.

FYI, The ballast resistor part number P5206436 that is specified for use with the orange ecu is listed as 1 ohm but the two that I have are marked as .25 ohm.
Author:  GuyLR [ Sun Apr 27, 2003 5:11 pm ]
Post subject: 
Thanks for the help. The new box cured my starting problems and the engine makes decent power again :D
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