Need continuity information for ignition switch
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Senior User
Joined: Apr 2012
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From: Spencer Mountain, NC
Need continuity information for ignition switch
After a couple of years on my rebuild project (74 F100 with rebuilt 351W and AOD) today was the day to "Fire it up". When I turned the ignition switch I got nothing in the start position but when I let off the key to the run position the solenoid (ignition relay) activated and started spinning the starter. Turned off the switch and it was still cranking. Mad dash to unhook the negative battery cable to shut it down. After a few electrical tests I determined that The wire to the "I" terminal was hot with the ignition switch in the run position. Tried a different ignition switch with the same results. Hard to believe both switches are bad. Can anyone provide me with continuity information for the ignition switch so that I can determine if the switch(es) are good or bad. Can't think of anything else that could cause this problem. ALL assistance will be greatly appreciated.
Cargo Master
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From: Kansas
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Senior User
Joined: Apr 2012
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From: Spencer Mountain, NC
Thanks dlburch but I have all the wiring diagrams. Need continuity specifications for the ignition switch i.e. which contacts have continuity with the key in all positions.
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Senior User
Joined: Apr 2012
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From: Spencer Mountain, NC
Thanks 77&79F250. The middle drawing looks like what I need. My switch has 6 terminals and although your drawing appears to have only 5 my old eyes may be deceiving me. If my switch tests out OK I will have to look further to determine why the wire at the "I" terminal is not hot in the "start" position but is hot in the "run" position,
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Senior User
Joined: Apr 2012
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From: Spencer Mountain, NC
Found my problem. Operator error!! Seems I had the two wires swapped on the starter relay. Had the "I" wire on the "S" terminal and the "S" wire on the "I" terminal. I had thought the "I" terminal was only "hot" when the switch was in the start position. WRONG. The wire to the "I" terminal is supplied voltage when the switch is in the run position. While running the continuity test on the switch the lights went on and I realized my mistake.
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Fleet Owner
Joined: Dec 2009
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From: NorCal
Found my problem. Operator error!! Seems I had the two wires swapped on the starter relay. Had the "I" wire on the "S" terminal and the "S" wire on the "I" terminal. I had thought the "I" terminal was only "hot" when the switch was in the start position. WRONG. The wire to the "I" terminal is supplied voltage when the switch is in the run position. While running the continuity test on the switch the lights went on and I realized my mistake.
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Aug 31, 2012 01:33 PM