No ignition power with old switch or new switch?

[nikwho]

Hello all,
So, I have just finished an engine swap in my '68 GMC. The truck has sat for 4 or 5 months without an engine. I finally got a fresh engine in the truck and got it all plumbed and ready to drive. When I turned the key, I received no power to the ignition. Have 12v coming into the switch, nothing to the pink ignition wire. Have 12v to the brown (I believe) ACC wire with the switch in the acc and on positions, loses power in start position, as it should. Engine will crank normally, but has no power to the ignition. I've gone as far as making a jumper wire that connects to the ignition wire at the back of the switch and charging it with 12v. Once 12v is applied to the wire, the engine will start right up.

So, it seems that something is prohibiting the ignition from getting voltage, by design. I'm just trying to figure out what. The truck was a factory standard, but now has an auto transmission with a column shift steering column. This column has a neutral safety switch that is not hooked up, with two purple wires coiled up together at the base of the column, right next to the neutral safety switch itself. This truck ran before with it configured like this, though I do need to incorporate the neutral safety switch as soon as I figure out what's going on.

So, I re-wired the new engine based off of my limited memory of taking it apart. I ran the purple wire that comes out of the fuse block across the firewall and to the starter. However, on the right side (passenger) of the transmission hump, there are three wires that come through the firewall. One is purple with an insulated rubber boot that appears to have a female blade connector inside. The second of the three is a black wire. The last one is a green wire that runs into one side of a double female connector. The other side of the connector has a short wire, with a round fitting to ground the wire to the chassis. I currently have none of these hooked up. I originally thought that these wires were all part of the HVAC system that I deleted while I had the engine out. I'm thinking that I'm wrong and that I need to figure out where these all go. Any help would be greatly appreciated!

Thanks much!
Nik

[nikwho]

Based off of this schematic, my issue is likely a balast wire. It looks like I need to hook up a blast wire and then wire my neutral safety switch in line with my ignition wire.

It'd be awesome if someone could explain the connection of the double female blade type connector that grounds to something on one side. Also, where would I attach the purple wire with the rubber boot?

[ray_mcavoy]

Hi Nik,

Since you are able to crank the engine over using the ignition switch, the purple wire is hooked up okay. This wire is only used to engage the starter and has nothing to do with feeding power to the coil. To connect up the neutral safety switch, you simply need to cut the purple wire near the switch, install terminals on each of the cut ends, and plug them into the switch.

That other purple wire with the rubber boot sounds like it might have been the feed to the heater/AC blower motor. Non-AC trucks used orange for this wire but I think it was purple with AC.

The pink wire on the back of the ignition switch should have power in both the "start" and "run" positions. If there is no power at the switch end of the pink wire then you have either (A) no power on the red wire feeding the switch, or (B) a defective switch, or (C) a bad connection where the pink wire plugs into the switch.

We can rule out (A) because you said you have power coming into the switch and we know the switch is passing that power on to the purple & brown wires as it should. And hopefully, having tried two switches, you can rule out (B) as well. But sometimes you can get new parts that are defective. So that leaves (C), a bad connection as the most likely problem. And if you can jumper power to the pink wire at the back of the ignition switch and get the engine to run, that means the rest of the pink wire (including the ballast / resistance wire portion that it connects to in the engine compartment) must also be okay since they are allowing the coil to receive power and the engine to run.

As for those "double female blade type connector that grounds to something on one side", are you referring to the terminals on the back of the ignition switch that connect to ground when it's in the "start" position? If so, one of them is used to temporarily activate the "temp" warning light on the dash (non-gauge clusters) and the other is used to temporarily activate the "brake" warning light. That allows the driver to see those lights come on while cranking the engine so they know the bulbs aren't burned out.

[nikwho]

Originally Posted by ray_mcavoy

Hi Nik,

Since you are able to crank the engine over using the ignition switch, the purple wire is hooked up okay. This wire is only used to engage the starter and has nothing to do with feeding power to the coil. To connect up the neutral safety switch, you simply need to cut the purple wire near the switch, install terminals on each of the cut ends, and plug them into the switch.

That other purple wire with the rubber boot sounds like it might have been the feed to the heater/AC blower motor. Non-AC trucks used orange for this wire but I think it was purple with AC.

The pink wire on the back of the ignition switch should have power in both the "start" and "run" positions. If there is no power at the switch end of the pink wire then you have either (A) no power on the red wire feeding the switch, or (B) a defective switch, or (C) a bad connection where the pink wire plugs into the switch.

We can rule out (A) because you said you have power coming into the switch and we know the switch is passing that power on to the purple & brown wires as it should. And hopefully, having tried two switches, you can rule out (B) as well. But sometimes you can get new parts that are defective. So that leaves (C), a bad connection as the most likely problem. And if you can jumper power to the pink wire at the back of the ignition switch and get the engine to run, that means the rest of the pink wire (including the ballast / resistance wire portion that it connects to in the engine compartment) must also be okay since they are allowing the coil to receive power and the engine to run.

As for those "double female blade type connector that grounds to something on one side", are you referring to the terminals on the back of the ignition switch that connect to ground when it's in the "start" position? If so, one of them is used to temporarily activate the "temp" warning light on the dash (non-gauge clusters) and the other is used to temporarily activate the "brake" warning light. That allows the driver to see those lights come on while cranking the engine so they know the bulbs aren't burned out.

Hello,
Thank you for taking the time to respond! So, the plug that I was talking about comes through the fire wall along with the wire with the boot that went to the blower motor. There are three wires together there. One is purple with an insulated rubber boot that appears to have a female blade connector inside. The second of the three is a black wire. The last one is a green wire that runs into one side of a double female connector.

So, I've built a short wire with 1/4" male blade connector ends on each. I have disconnected the ignition switch harness from the old ignition switch. I plugged one end in to the connector for the red 12v bat wire and jumped it over to the pink wire terminal. Then I connected my remote momentary push button starter switch between the red wire and one of the terminals above it (I am forgetting what color wire came from it at the moment) and the truck fired right up! So, with the switch bypassed and with power jumped to the ignition wire, it worked as I would expect. When I jumped the two wires (red and pink) my gauge lights came on, the radio started playing music and the HEI coil obviously received power. The previous owner piggy backed a 12-14ga. wire off of the pink wire, through the fire wall and directly to the HEI coil lead.

Before I bought the new switch, I used my continuity checker and touched one lead to the switch terminal for the battery and the other lead to the switch terminal for the ignition wire. I turned the switch to run and start. Neither audibly indicated continuity. I performed the same check between the battery terminal and the brown ACC wire, which indicated continuity with the switch turned to ACC and run, but not in the start position, as it is supposed to. I have yet to check the new switch. I had to come to work. That will be my next check.

As soon as the new switch didn't work, I assumed that my problem was not the switch. I assumed that one of the other leads on the switch needed 12v coming in to the switch to tell the switch that it was okay to send power to the ignition. I just thought that I may have left something disconnected. The old ignition switch worked perfectly when I pulled the old engine.

Perhaps I need to check continuity between the pink ignition wire and ground? As The ignition would likely not see power if the pink wore was grounded? I remember thinking that I smelled an "electrical" smell when I jumped power to the pink wire, but when I stopped and looked around for smoke or other bad signs, I found nothing and continued to work after finding nothing. I have a feeling that it's not the switch, but will need to test more to figure it out. I was hoping that someone would read this and make sense out of the symptoms and know what I may have not hooked up correctly.

[ray_mcavoy]

You're welcome Nik,

Yes, that purple wire that comes through the firewall and has the rubber boot connector sure sounds like the one that would have gone to the blower motor. I think the other two wires (black & green) may be the ones that went to the electric clutch on the AC compressor.

Your jumper wire & push button starter testing all seems to confirm that the wiring to the starter & ignition is hooked up okay. If that pink ignition wire were shorted to ground, I think you would have had some serious sparking when you used the jumper wire to connect it to the red power feed (and it probably would have blown the fusible link out near the battery that protects the red wire).

The continuity test on the old ignition switch does point to that being bad. Doing the same test on the new switch would be a good idea (you can get a bad one sometimes).

If I remember correctly, these ignition switches do have 2 terminals for the red battery feed wire(s). Most applications only have one red wire running to one of those terminals and they are internally connected inside the switch. But I suppose there is the possibility that the new switch is configured a little differently (with those terminals separate) and uses one of them to feed the purple (start) and brown (accy) wires while using the other to feed the pink (ign) wire. If that were the case, you would have to connect a permanent jumper wire between those 2 battery feed terminals on the back of the switch.

[VetteVet]

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Originally Posted by nikwho

Hello,
Thank you for taking the time to respond! So, the plug that I was talking about comes through the fire wall along with the wire with the boot that went to the blower motor. There are three wires together there. One is purple with an insulated rubber boot that appears to have a female blade connector inside. The second of the three is a black wire. The last one is a green wire that runs into one side of a double female connector.

It looks like this is your AC compressor clutch, blower fan and ground wires.
Check this diagram on the left side and left upper.



You can confirm the purple wire if it has power with the heater switch on full power. If you don't have the AC harness from the fuse panel as shown in the diagram, you will have to adapt for that.


So, I've built a short wire with 1/4" male blade connector ends on each. I have disconnected the ignition switch harness from the old ignition switch. I plugged one end in to the connector for the red 12v bat wire and jumped it over to the pink wire terminal. Then I connected my remote momentary push button starter switch between the red wire and one of the terminals above it (I am forgetting what color wire came from it at the moment) and the truck fired right up! So, with the switch bypassed and with power jumped to the ignition wire, it worked as I would expect. When I jumped the two wires (red and pink) my gauge lights came on, the radio started playing music and the HEI coil obviously received power. The previous owner piggy backed a 12-14ga. wire off of the pink wire, through the fire wall and directly to the HEI coil lead.

Here is the replacement switch and keep in mind that they vary a little so I will explain what the wires go to.



1.The large red wire 12 Gauge is the main power wire from the battery.
2.The pink wire goes to a tee in the harness that connects the fuse panel, the ignition to the coil (HEI distributor) and the cluster panel for the dash gauges. Some switches have a terminal with a red wire in the harness to do part of that.
3.The small double brown wire is for the brake warning light in the dash and it is grounded by the switch when the starter(12 gauge purple is engaged in the start position). There is no connection to the purple and brown wires, only the brown wires are grounded. This was explained by Ray in his reply.
4. The two green wires are for the temp light in the dash, they are also grounded by the switch during starting just like the two browns. The difference is they are not there for gauge dashes that use the temperature gauge.
5. The 12 gauge purple wire is the starter solenoid wire which goes to the neutral start switch then through the firewall to the solenoid.
6. The large 12 gauge brown wire is the power feed wire to the fuse panel for the turn signal, the heater switch, the wiper motor and other accessories.
7. The small brown wire connected with it is for the resistance to the external voltage regulator and the exciter wire for the alternator. Normally it is a 24 gauge yellow and black stripe wire but it appears to be a brown wire in the switch picture. It is shown in the diagram I posted below.

Top left.


Here is a cropped picture.





Here is a picture of the paths these wires take in the harness to the tees and to the fuse panel and the horn relay and the headlight switch.

The black arrows show the large brown ACC wire from the key switch and into the fuse panel. The large red wire tees to feed the horn relay, the fuse panel the headlight switch, and of course the key switch.





Before I bought the new switch, I used my continuity checker and touched one lead to the switch terminal for the battery and the other lead to the switch terminal for the ignition wire. I turned the switch to run and start. Neither audibly indicated continuity. It should have . I performed the same check between the battery terminal and the brown ACC wire, which indicated continuity with the switch turned to ACC and run, Yes. but not in the start position, as it is supposed to. I don't think it has continuity in the start pos. I have yet to check the new switch. I had to come to work. That will be my next check.

As soon as the new switch didn't work, I assumed that my problem was not the switch. I assumed that one of the other leads on the switch needed 12v coming in to the switch to tell the switch that it was okay to send power to the ignition. See item 1 in the first paragraph. I just thought that I may have left something disconnected. The old ignition switch worked perfectly when I pulled the old engine.

Perhaps I need to check continuity between the pink ignition wire and ground? The pink wire is a hot wire don't ground it .As The ignition would likely not see power if the pink wore was grounded? The ignition will not see power if the pink wire is not connected to the battery wire via the key switch, if you ground it you will smoke it. I remember thinking that I smelled an "electrical" smell when I jumped power to the pink wire, but when I stopped and looked around for smoke or other bad signs, I found nothing and continued to work after finding nothing. I have a feeling that it's not the switch, but will need to test more to figure it out. I was hoping that someone would read this and make sense out of the symptoms and know what I may have not hooked up correctly.

Hope this helps. VV

[nikwho]

Thanks guys! I truly appreciate your help! I was hopeful that I just left something not connected, as that would be a quick, easy fix. However, I can usually work my way through things like this and didn't see anything wrong with the way that I had everything hooked up. It just seems super weird that It worked perfectly when the truck was parked a few months ago, then the ignition switch some how fails while the truck sat in my climate controlled garage. And, on top of that, I would have had to have received a faulty switch. I'm just not thinking that this is the case. Tomorrow morning I am going to pull the wire harness off of the back of the switch and test it. I have a suspicion that there is an issue with the wire harness that clips into the back of the switch. When I tested the original switch, the wire harness was clipped into place and I stuck my multimeter probes into the back of the harness.

Anyhow, still really weird being that I didn't mess with the wiring inside of the cab while the truck sat engine-less. But, I will continue testing and report back what is keeping this thing from running.

Thanks so much for your guys' help!

Nik

[nikwho]

Well, I got home today and started testing everything. I removed the ignition switch and tested both the old and new one. Both tested fine. After still having no power upon reassembly, I looked close and realized that the ignition wire was plugged into the harness in the wrong spot. So, when I tested th ignition with the harness plugged in, the ignition wire wasn't actually connected to the ignition terminal on the switch. So, I had removed this wire from the switch harness to clean up some of the previous owners messy electrical connections. I had it clear in my head what terminal the connector needed to plug in to, but got mixed up when I laid on the bench seat and crawled under the dash. So, I'm just a doofus, that's all that was wrong with my truck! Got to put some miles on it today with my 5 year old son, who lived every second of our drive! Thanks much for your guys help and thoughtful responses!

Nik C.

[ray_mcavoy]

Cool, glad to hear it was an easy fix! Yeah, things can get a bit disorienting when you're working up underneath the dash like that.

[nikwho]

Yes, they can. I feel kinda foolish for throwing parts at it and not catching my mistake before, but oh well. I have a spare ignition switch now.