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Posted by Todd Wilson [71.158.209.57] on Thursday, March 25, 2010 at 00:28:48 :
In Reply to: 1973 W200 electrical problem posted by Bill Kerfoot [66.74.149.93] on Wednesday, March 24, 2010 at 20:50:43 :
Well I had the same problem on my 74. Thought I had an ignition switch problem. They are very expensive items to replace and a pain to get to in the column. Was not my problem.
What I did find was and you will notice your ignition switch has Ignition 1 & 2, battery, start and acc. contacts and wiring to it. All your ignition and charging wiring run thru this area. Included in this circuit of wiring is the ECU and ballast resistor. Its all connected and has to work together or it will not run.
My engine harness had some insulation on wiring that was old brittle,wore away or what have you. it ended up shorting and burning. I took the engine harness clear off the truck,. Unwrapped the old electrical tape covering off the whole thing. What I found was brittle old wiring. Where it curved around the end of the engine at several spots I had bad insulation. I replaced a few spots. Heat shrink tubed the rest adn rewraped with new tape.
Your firewall connectors are a place that can create problems. Those contacts on the connectors are old. they corrode a tad bit and this created resistance which created heat. This situation could be enough to created enough heat to burn something in 2. I solved my bulkhead connector problem by spraying it with Deoxit. Its a "tuner wash" of sorts I used on my old tube radio hear. It cleans,lubes and takes the oxide off connectors. This alone perked up my entire electrical system.
I do not know where you could just order a new harness for these 70's trucks. Try and fix what you got with heat shrink tubing or replacing a section.
Find the short!!!! The key and alternator are the ends of the circuit.Volt reg, Ballast,ecu or points and coil are all on this circuit.
I have the electrical schematic online if you need it. I can email you the pages.
Todd
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