Ignition switch connection

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3406pk

3406pk

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I have 1972 Challenger 340 w 4spd that I am completing the rebuild. I have started engine and broken in cam. While doing the tuning it was hard to start. I found that the voltage to coil and resistor was lower than battery by 1.5 to 2 volts. Further testing at connector at steering column going to and from ignition switch, yields 12.7 v to switch on red wire. But the brown and blue wires coming from switch are 1.5 volt lower than battery. So I think the contacts at ignition switch are corroded. There are 2 questions: Is there any shortcut way to clean the ign switch connections without taking steering wheel & all related items apart? Also I have Plymouth shop manual for 1970 and 1973 Dodge chassis manual, would the procedure from the 73 apply to the 1972 Dodge for access to switch? I can't find pdf manual for 1972.
 
Your reasoning makes sense but I'm not sure everything is accounted for. Be best to check the assumptions about what is connected when.
3406pk said:
Further testing at connector at steering column going to and from ignition switch, yields 12.7 v to switch on red wire. But the brown and blue wires coming from switch are 1.5 volt lower than battery.
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Need to be sure what's going on here.
Usually Blue wires out are Ignition 1, and Brown is Ignition 2.
They only connect through the ballast resistor. So if current is flowing, voltage on one should be system voltage and the voltage on the other should be lower.

Key OFF,
Power feed to switch should be same voltage as battery. Ammeter should be zero (no current flowing). Wire is 12 awg Red.

Key RUN, Engine not running.
Power feed to switch should be same voltage as battery. Ammeter should show about 4 amps current flowing out.
Ignition 1 (Run) should be almost the same voltage as battery.
Ignition 2 should be measurably less than battery.
Accessory should be the same voltage as Ignition 1.

Key in START
Power feed to switch should be same voltage as battery. Ammeter should show about 3 amps current flowing out.
Ignition 2 (Start) should be almost the same voltage as battery.
Starter relay (yellow) should be almost the same voltage as battery.
Ignition 1 (blue) should be measurably less voltage than battery.

During Start, the battery voltage will drop several volts. If it goes below 9.5 Volts during cranking indicates a weak battery.
 
Mattax said:
Is this drop in voltage based on direct measurement? That is, one lead on the battery positive and the other on the connector at the coil with the key in start?
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Yes, that was direct measurement. When I measured in start position, I disconnected starter solenoid wire. So there was no drop in battery volts.
Thanks for replys.
 
That would reduce the drop in voltage at the battery since the load is much smaller.
It's still a comparison if both measurements are to ground.
Direct is when the leads are connected as described above so the meter will show the difference in voltage. That is the meter will read 1.5 Volts. between battery and brown, and 0 between battery and Red at the switch.

I'm still puzzled why both Run and Start ignition wires were at the same voltage - assuming that's what Blue and brown connect to. Only one should be lower than battery voltage.
 
Did you check the infeed to the switch with the switch powered on? Also did you check both the key side and harness side of the switch connector? If so and that shows no drop, then it surely is in the switch--not really uncommon. One way around this is to put a couple of relays in there.........one to fire accessories and one for the IGN1 feed
 
67Dart273 said:
Did you check the infeed to the switch with the switch powered on? Also did you check both the key side and harness side of the switch connector? If so and that shows no drop, then it surely is in the switch--not really uncommon. One way around this is to put a couple of relays in there.........one to fire accessories and one for the IGN1 feed
Click to expand...
The volt was checked w power to switch. Only checked key side of connector for ign1 &ign2 since it showed the 1.5 v drop coming from switch. If I get switch connection good then I'll check both sides of harness connector.
 
Just curious, are you stil using the old school big heavy original mopar starter? They take lots of juice just by themselves.

Have you tried the mopar mini starter, like out of the Dakotas.

They spin faster, take way less juice, and weigh a lot less than the original. Consequently taking less juice provides you with more juice for your ignition system.

Best upgrade for the mopars, start like they have fuel injection.
 
George Jets said:
Just curious, are you stil using the old school big heavy original mopar starter? They take lots of juice just by themselves.

Have you tried the mopar mini starter, like out of the Dakotas.

They spin faster, take way less juice, and weigh a lot less than the original. Consequently taking less juice provides you with more juice for your ignition system.
Best upgrade for the mopars, start like they have fuel injection.
Click to expand...
I have one on my Duster, really like it & needed for headers. May consider for this Challenger.
 
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