Ignition switch test

[68bigblock]

I'm having periodic trouble with my 70 challenger starting. (my b body is running great), first time I noticed a problem I turned the key and nothing no crank or anything so I checked the battery cables they were good tried it again and it started, the next time I was driving it and it died the fusable link burnt up, replaced that then car cranked but wouldn't start, so I check the coil, ballast resister with a multi meter and they checked out fine never really touched anything, then tonight I went to do a spark check cranked it over and it started right up, so I,m thinking ignition switch is there a way to test it in the car? would a bad switch burn up a fusable link? any suggestions are welcome

 

[Badvert65]

First thing I would check would be the ignition ballast resistor. Your symptoms are typical of a defective resistor. Could be something else but I would start there.

 

[miller]

Just a start. Think if that fusible link goes out...there's a problem somewhere. You've got at least one wire that's heating up, due to a poor connection, corrosion, or the like.

You might un-plug the wiring socket from the ignition switch, and take a look. Any signs of corrosion, burnt wiring, will give you a clue of what's going on. Also look at the firewall block, un-plugging the sockets to look.

You either have a bad piece of wire, or a bad switch. Concentrate on the 'ignition system' part of your wiring.

 

[68bigblock]

it died again today, to keep it running I had to hold the key between run and start. when I got it home I checked the ballast resistor again and it checked out fine 1.2ohms, prior to this I checked the ignition harness and I did notice some discoloration on the supply wire(red) connectors they were getting hot so I cleaned them up, the main bulk head connectors looked good. I have a new ignition switch on order. Anyone have any suggestions on what else I could check in the mean time?

 

[khryslerkid]

Sounds like a bad switch if you have to hold it in that position.

 

[nm9stheham]

The later symptoms (holding the key funny) indicates the ignition switch as noted. It is not worth the time to troubleshoot the switch; it is just a replacement item if it gets suspect.

The possible short could be something breaking inside the ignition switch and erratically shorting, or it could be something else shorting in the harness that connects via the ignition switch; that includes the ignition system as well as the alternator output and filed supply and voltage regulator power feed, and the starter relay coil. You can check the schematic to see what all is fed by the ignition switch.

It could be that the fusible link just finally failed on its own, and the heating on the wire to the igntion switch is just from corrosion and heat build-up in the switch. But I would not take that chance; I would be far more worried about a short somewhere. That could burn your nice car to the ground....I would be tracing all of the wires out of the igntion switch and unwrapping the harness, looking for a chafed wire, melted insulatoin between wires, and any cuts in the insulation. Go all over.

I'd disconnect the battery when not being driven and carry a couple of CO2 exinguishers with me 'til I was sure this was solved. Best of luck in this!

 

[68bigblock]

I finally got the switch changed and the problem is still there, I have to hold the key between run and start to keep it running. is there any other ideas out there?

 

[aldal]

Don't know :dontknow: but this is a very interesting subject....

 

[nm9stheham]

Questoin: When you are holding the key switch between RUN and START posotions to make this run, is the starter still engaged or not?

Electrical: There are 2 lines from the ignition switch to the ignition and ballast; both go via the bulkhead. IGN1 is the blue wire that goes to the ballast and also to the voltage regulator. IGN2 is the brown wire that goes to the other end of the ballast, where the wire to coil + conencts. IGN 2 is on and IGN1 is off when starting; IGN1 is on and IGN 2 is off when running. The usual problem is that the car will start because IGN2 is good and feeds +12V to the coil directly for starting but IGN1 is bad and does not supply +12 to the other end of the ballast when the key is released to

You reported checking the voltages to ballast, coil, etc but it would help to repeat the checks with the voltmeter with the key in RUN but the engine not started and let us know the voltages at both ends of the ballast resistor. And then disconnected the brown wire form the starter relay to the starter and repeat those same 2 voltage checks with someone holding the key in the START position.

If the IGN1 (blue line) is not good in the RUN position, then check the wines on both sides of the firewall connecoitn for the blue (IGN1) wiring.

Mechanical: If the electical side is not OK for IGN1, then also look at the key lock itself to see if it is worn and not holding the ignition switch in the right position, or if the mechnical connection between key switch and electical ignition switch is mis-indexed..

 

[68bigblock]

no you can let it off enough that the starter is not engaged. across the ballast in run I get nothing, in start I get 4.9v from the ballest to the - coil in run nothing, from ballast to - coil in start 9v. with the brown wire disconnected I can hear a click when I turn the key into the spring section of the switch and another click when I turn it all the way and when I release I hear click about half way through the spring section and another at the run position.

 

[68bigblock]

I pulled the switch out and tried it and I had to hold it slightly to the start position so it not the key mechanism it got to be electrical

 

[68bigblock]

I was doing some continuity test and I noticed both ING1 and ING2 go to ground on the dash side of the bulk head (I unplugged the engine side) is that correct? and my manual says ING1 is Brown and ING2 is blue but every thing else says the opposite