Faulty Ignition Switch

[73EStroker]

Well had to try and start the beast today to move it to another shed in the snow and sub zero temperatures. Car does not seem to fire while cranking but if the start position is released at the correct time then she fires. (1973 system converted to Mallory but using both wires coupled together because the ignition contact releases in start position with the start aux making contact. Blue and Brown wires). Did this a couple of times last year. So the analysis today has 12.6 volts at the starter relay and with the key in ignition position I get 10.8v at the firewall plug (both sides) and with the key in start position I actually get 11.1V(both sides). Firewall red and black wires go straight through IE no spade terminals just lug and bolt connections. What this leads me to believe that as there is no other loads on the battery the ignition switch contacts have high resistance joints. Seems unlikely that another problem is elsewhere if there is good voltage drop on both contacts. I would appreciate it if I could get the Mopar part # please so that the local dealer can get a new switch for me. PITA to get this stuff from south of the border for small orders such as these.
Thanks all

[dodj]

Did you check the connector at the bottom of the column? You could have a poor connection there causing the problem.

[73EStroker]

Dodg - I did. Would be very odd if both connections were bad. I will check again though. So is the concensus so that the switch even with those thousands of cycles still be ok. Does anyone else have the same issues (measuring the voltage before the ballast resistor of course.)?
I do ot have the resistor with the Mallor system

[Bullitt-]

One solution is to add a relay that is energized by the ignition but connects power directly from the battery to ensure full voltage.
There was a company at one time offering kits & I have read about making your own, not very complicated.

[73EStroker]

Yeah Bullitt - I thought about the relay thing but that becomes another electrical part that has to hold in to make the car run. I could add the big secretly located bypass switch in case the relay failed I guess. Relay system is easy as I have done the fuel pump and the headlights high/low beams. Big difference.

[Bullitt-]

I would argue that it would make your ignition more reliable, other than the possibility that the relay itself could fail you are making it easier for the 40 year old switches & connections to work.

[73EStroker]

I decided to go with the relay and simply carry a spare. Will post how this worked. Further problems will see me replace the ignition switch etc. I will firstly check the connections along the steering column though.

[dodj]

Just  FYI  for you 73EStroker,
With the ignition switch in my car that works fine, the resistance from red to blue (run) was 1.1 ohms. From red to brown(start), it was 2.2 ohms. For a connection that should be darn close to zero I thought those numbers were a bit high. I spent some time with contact cleaner and a needle file on the female column connector, and got the numbers both down to 0.2 ohms. One interesting observation - when turning the ignition to start, the resistance on the brown wire would drop to 0.2 ohms, but if I pushed hard against the end of it's travel, the resistance started to climb up. 5.6 ohms. 

[73EStroker]

So that means the terminals in the plugs were part of the problem. also the switch is probably a culprit as well. 35+ years of being rotated and switching DC current has probably taken it's toll. I will recheck the plug connections on the column then.