Ignition Switch Wiring - A do over

[71CHEVYSHORTBED402]

1971 C-10

I added a thread last night, and despite Randy500's attempt to walk me through it, I was pretty well off in left field. So this is a do over.

I'm in the process of identifying all the wires, and am currently at the ignition. Anyway, this may be helpful to others. I still have one question concerning a second purple wire (explained in the image).

This has been updated: Thanks for any input/corrections.


For reference:

[custom10nut]

Great info to have.

[VetteVet]

Thanks for the props.

Looks like you have it sorted out except for the question on the reverse lights and neutral start switch purple wire.

They have nothing to do with each other except the wires (purple and dark green) share the same switch the NSS. The reverse lights get their power from the fuse panel and the revers lts fuse. It's a dark green wire that runs to the neutral start switch and from there to the rear back-up lights. Here's a pic.

You can see the purple wires and barely see the greens. There should be a light green wire from the NSS that runs to the rear back-up lights. It's a key on hot deal so they only work with the key on and the gear shift in reverse.

[71CHEVYSHORTBED402]

Thanks Vette. This cab is nearly stripped less wiring, windows and gas tank. The NSS is left hanging, and I'll look into it tomorrow, thank you.

After I wrote the above I thought no, that purple wire is probably not why my reverse lights didn't work. Speak of wires I'm green. Speak of purple wire, it's my understanding the ignition switch had two purple wires for automatics. Mine had one, for the solenoid. What am I missing?



Someday I may quiz you on HEI. I've always heard 10 gauge wire was a must, but judging by a few posts, including yours, doesn't appear necessary.

[VetteVet]

Originally Posted by 71CHEVYSHORTBED402

Thanks Vette. This cab is nearly stripped less wiring, windows and gas tank. The NSS is left hanging, and I'll look into it tomorrow, thank you.

After I wrote the above I thought no, that purple wire is probably not why my reverse lights didn't work. Speak of wires I'm green. Speak of purple wire, it's my understanding the ignition switch had two purple wires for automatics. Mine had one, for the solenoid. What am I missing?

I only know of one from the factory, looking at the wiring diagram, it shows a solid purple wire and a dotted line purple wire which represented the purple wire for the manual transmissions. Seeing both of them might be where the confusion comes from.



Someday I may quiz you on HEI. I've always heard 10 gauge wire was a must, but judging by a few posts, including yours, doesn't appear necessary.

There''s been a debate on the size wire to use on the HEI distributors. As you
know they require a full 12 volts to work properly. Any chart you can find will show that 12 awg is big enough to carry the current they will draw without any significant voltage drop.Some guys like to use a 10 awg but it's overkill IMO. Also there's a debate about using a fuse in the wire. It's OK too but the factory never did. I've heard some guys say you have to use a 30 amp fuse to avoid resistance which I say is BS cause there is no resistance in any fuse that I've ever measured.

One of the biggest mistakes that a lot of guys make is to just use the old coil + wire, without realizing that it is a resistor wire, and will drop the voltage to the HEI coil to about 9 volts, which may fire the distributor but it'll be a weak spark. Then they get misfires and hard starts and other problems.

There's about three ways to wire up the HEI.
1. Solder a new wire into the pink wire on the key switch.
2. replace the resistance wire in the engine bay at the firewall block.
3. run a new wire from the fuse panel IGN Unfused terminal on the fuse panel to the distributor.

You can't cut the pink wire if you solder the HEI wire into it cause it also feeds the fuse panel. Check the diagram below. Follow the pink wire 5th from the top down to the junction dot and one leg goes left to the inside of the firewall block to the resistance wire and the other leg goes down to the fuse panel and then over to the dash cluster plug for the gauges.

[71CHEVYSHORTBED402]

Any chart you can find will show that 12 awg is big enough to carry the current they will draw without any significant voltage drop. Some guys like to use a 10 awg but it's overkill IMO. Also there's a debate about using a fuse in the wire. It's OK too but the factory never did. I've heard some guys say you have to use a 30 amp fuse to avoid resistance which I say is BS cause there is no resistance in any fuse that I've ever measured. Good to know.


There's about three ways to wire up the HEI.

1. Solder a new wire into the pink wire on the key switch. This is how the current HEI was done. Another guy another time. I'll run with #2 or #3. It's worth mentioning I plan to replace everything with a M&H or American Autowire kit. Apparently they provide for HEI as well.


2. replace the resistance wire in the engine bay at the firewall block. Didn't know that was called a F/W block until now. Nice to have proper labels. This sounds the most clean. I've identified all the wiring in the engine bay, and there's no sign of a resistance wire. Seems the engine bay is straight forward, less a mystery wire cut on the TCS relay.............By replace the wire in the engine bay at the firewall block, you mean?


3. run a new wire from the fuse panel IGN Unfused terminal on the fuse panel to the distributor. Not quite as clean as #2, but clean and convenient, and even sounds right. I've heard this mentioned before and appreciate the confirmation. I may be going through the F/W anyway for an HEI kill switch.


You can't cut the pink wire if you solder the HEI wire into it cause it also feeds the fuse panel. To me this means the schematic for the Pink wires should be factory when I rebuild this truck. EDIT: This may be where my confusion begins........HA! sorry. If I hadn't mentioned I'm rather green.


Check the diagram below. Follow the pink wire 5th from the top down to the junction dot. One leg goes left to the inside of the firewall block to the resistance wire. A resistance wire that appears to be missing on the F/W side, as stated. I still have to pull the entire panel off the F/W. Hopefully that clears things up.


and the other leg goes down to the fuse panel and then over to the dash cluster plug for the gauges. I'm a little confused at this point. Hopefully the images below explain why and help, and your input is appreciated. Incidentally, any advise on the SECOND 20 AWG Purple mystery wire I appear to be missing for the Neutral Safety? If I'm supposed to have it, then is it connected with the other Purple wire for the Solenoid at the Ignition Switch? Where it goes from there I don't know. I do have some schematics available, in the manuals. They're something to get used to with a good dash of patience

Appreciate it Vette, thank you.

[VetteVet]

When your truck came from the factory it had points in the distributor and an ignition coil that would not sustain a constant 12 volts to it. The factory solved this by installing a 1.8 ohm resistance wire in the firewall terminal block to drop the voltage to the coil for normal running. This wire was a white/orange/purple wire which is shown below as a cloth covered wire and over the years has turned mostly white.



The factory also wanted to get a full 12 volts to the coil for a hotter spark when starting so they installed a connecting wire from the starter "R" terminal which was a yellow or yellow with a black stripe wire to achieve this purpose.
When HEI ignition was added the distributors needed a full 12 volts all the time when starting and running. They eliminated the resistance wire and the connecting wire from the starter.

This diagram shows the resistance wire and the connecting wire on the middle of the diagram and on the top by the starter.



\

Unless someone needed another purple wire from the ignition for some unknown purpose there was only one 12 ga purple wire on the key switch.
It ran from the ST terminal on the key switch to the NSS on the steering column (automatics) to the firewall block and on to the starter solenoid.

The only 20 gauge wire on the key switch is the brake warning wire, which runs to the switch and joins another 20ga tan wire, that runs to the dash cluster to the brake warning light. When the key switch is turned to start
a circuit in the switch grounds this tan wire and turns on the light, to test the bulb, to check that it isn't blown.

whenever the fluid levels in the brake distribution valve gets uneven a switch in the valve will ground this wire and turn on the light.

[71CHEVYSHORTBED402]

Originally Posted by VetteVet

When your truck came from the factory it had points in the distributor and an ignition coil that would not sustain a constant 12 volts to it. The factory solved this by installing a 1.8 ohm resistance wire in the firewall terminal block to drop the voltage to the coil for normal running. This wire was a white/orange/purple wire which is shown below as a cloth covered wire and over the years has turned mostly white.

Attachment 1625034

The factory also wanted to get a full 12 volts to the coil for a hotter spark when starting so they installed a connecting wire from the starter "R" terminal which was a yellow or yellow with a black stripe wire to achieve this purpose.
When HEI ignition was added the distributors needed a full 12 volts all the time when starting and running. They eliminated the resistance wire and the connecting wire from the starter.

This diagram shows the resistance wire and the connecting wire on the middle of the diagram and on the top by the starter.


Attachment 1625035
\

Unless someone needed another purple wire from the ignition for some unknown purpose there was only one 12 ga purple wire on the key switch.
It ran from the ST terminal on the key switch to the NSS on the steering column (automatics) to the firewall block and on to the starter solenoid.

The only 20 gauge wire on the key switch is the brake warning wire, which runs to the switch and joins another 20ga tan wire, that runs to the dash cluster to the brake warning light. When the key switch is turned to start
a circuit in the switch grounds this tan wire and turns on the light, to test the bulb, to check that it isn't blown.

whenever the fluid levels in the brake distribution valve gets uneven a switch in the valve will ground this wire and turn on the light.

I see, that resistance wire is on the RH (truck side) of your terminal block. You have five wires, and I do as well. Here's what I've got:

1. Purple12 to Starter

2. Brown/White 18ish for TCS

3. Dark Green20 for Temperature Sensor

4. Tan20 for Combination Valve

5. Looks Light Red 18-20 AWG, but I think it's a safe bet it's Pink. A picture is below. The kicker is it says Resistance on the wire. Perhaps it was a replacement, but safe to say this is the wire I was "missing".

Thing about it is, and yeah I'm slow................I have HEI, and this "resistance" wire was connected to my starter. Anyway, WOW, you're saying this is incorrect right? it should be removed. I'm surprised it's worked for so long with no problems, but that said, I think I just got a clue why the image above (Post 7 Image 1) for Pink appears to be missing a connection..............Do you agree?

Also, concerning "option 1 for HEI", are you saying to replace this resistance wire with a 12 AWG for HEI?

Concerning the Purple Wire (a.k.a. ST, SOL). Either I misread the posts or am just plain green on the subject of wiring. As you're probably aware by now, it's likely the latter. Takes me a while sometimes, but I get there eventually. Thank you for clearing that up. I'll update the image at top and put the Ignition Switch to rest. Appreciate your help and patience.

[VetteVet]

Originally Posted by 71CHEVYSHORTBED402

I see, that resistance wire is on the RH (truck side) of your terminal block. You have five wires, and I do as well. Here's what I've got.

That isn't my firewall block but it is like factory for a light dash, not a gauge dash so it will be slightly different. The resistance wire is indicated by the line labeled 1.
Your resistance wire is most likely a replacement for the cloth one in my picture. It would run from the key switch as a pink wire to the inside of the cab on the firewall block, then goes to the starter, with a separate wire going to the OEM ignition coil on the positive terminal. The diagram below shows this. Keep in mind that the wires changed slightly over the years. For instance you say you have a tan wire with white stripe for the TCS. You should check that because I''ve read that the TCS had it's own harness. I can't confirm that though so don't quote me.

1. Purple12 to Starter ----I agree

2. Brown/White 18ish for TCS----not sure on this.

3. Dark Green20 for Temperature Sensor----yes

4. Tan20 for Combination Valve---yes

5. Looks Light Red 18-20 AWG, but I think it's a safe bet it's Pink. A picture is below.---Looks red to me.

The kicker is it says Resistance on the wire. Perhaps it was a replacement, but safe to say this is the wire I was "missing". ----sounds like it was

Thing about it is, and yeah I'm slow................I have HEI, and this "resistance" wire was connected to my starter. Anyway, WOW, you're saying this is incorrect right?---No I believe it is correct but you don't need it with HEI
it should be removed. If it is the one I think it is. It's the one that gets replaced with a 12 gauge wire to the HEI BAT terminal in step 2 I mentioned above.

I'm surprised it's worked for so long with no problems, ---It just runs from the key to a dead terminal on the starter. Since you had another wire for the HEI ignition, the resistance wire was not doing anything. Do you follow?

but that said, I think I just got a clue why the image above (Post 7 Image 1) for Pink appears to be missing a connection..............Do you agree?----I'll have to go back and look at the thread

Also, concerning "option 1 for HEI", are you saying to replace this resistance wire with a 12 AWG for HEI? ----Yes see the third paragraph above.

Concerning the Purple Wire (a.k.a. ST, SOL). Either I misread the posts or am just plain green on the subject of wiring. As you're probably aware by now, it's likely the latter. Takes me a while sometimes, but I get there eventually. Thank you for clearing that up. I'll update the image at top and put the Ignition Switch to rest. Appreciate your help and patience. ----My pleasure

Here's a diagram showing the wires from the firewall block. This one is for the gauge dash. See the black wires for the battery gauge.



Notice the white/orange/red/ resistance wire from the FB to the starter. Then see the wire to the ignition coil ties into it. You get 12 volts while starting and 9 volts during normal running. That's why you need to replace that wire or run a new one to the HEI distributor.

I can identify the other wires if you need me too.

[VetteVet]

Your question about post 7 image one, Is not according to the diagram for the anti-dieseling relay. The diagram shows the pink wire running from the anti-dieseling relay to the AC switch. There are two relays in the AC circuit and the power wire is orange and it is connected to CIG terminal on the fuse panel and runs to the fan relay, then jumps over to the AD relay.
Who ever wired yours up used the IGN unfused terminal which would also work but is not according to the diagram.

Find the orange wire at the CIG and follow it up to the main relay, then jump over to the AD relay. The pink wire is right there so follow it back down to the AC heater fan switch.

[71CHEVYSHORTBED402]

Originally Posted by VetteVet

Here's a diagram showing the wires from the firewall block. This one is for the gauge dash. See the black wires for the battery gauge.

Attachment 1625441

Notice the white/orange/red/ resistance wire from the FB to the starter. Then see the wire to the ignition coil ties into it. You get 12 volts while starting and 9 volts during normal running. That's why you need to replace that wire or run a new one to the HEI distributor.

I can identify the other wires if you need me too.

Thanks Vette. I'll bet you can and it's appreciated.

[71CHEVYSHORTBED402]

Originally Posted by VetteVet

Here's a diagram showing the wires from the firewall block. This one is for the gauge dash. See the black wires for the battery gauge.

Attachment 1625441

Notice the white/orange/red/ resistance wire from the FB to the starter. Then see the wire to the ignition coil ties into it. You get 12 volts while starting and 9 volts during normal running. That's why you need to replace that wire or run a new one to the HEI distributor.

I can identify the other wires if you need me too.

BINGO..............I got it. Comedy of errors surrounding that Resistance wire. My wife says it's pink BTW. Doesn't matter.

I didn't realize until today that resistance wire had a butt connector with a yellow wire to the starter. I've always "known" it to be the yellow wire to the starter. So every time someone mentioned "yellow starter and coil", well, between not having a coil and being an amateur, have to say, I gots confused.

I can't tell you how many times I've handled the starter, only to reconnect the "yellow" resistance wire resisting nothing.

Thank you for clearing things UP.

[71CHEVYSHORTBED402]

Originally Posted by VetteVet

Your question about post 7 image one, Is not according to the diagram for the anti-dieseling relay. The diagram shows the pink wire running from the anti-dieseling relay to the AC switch. There are two relays in the AC circuit and the power wire is orange and it is connected to CIG terminal on the fuse panel and runs to the fan relay, then jumps over to the AD relay.
Who ever wired yours up used the IGN unfused terminal which would also work but is not according to the diagram.

Find the orange wire at the CIG and follow it up to the main relay, then jump over to the AD relay. The pink wire is right there so follow it back down to the AC heater fan switch.


Attachment 1625455

Ah.............Ahhhhhhhhhhhhhh, alright, I let this soak in a while and did some prep. Today I decided to include the color of each wire as I tag them, due to be colored challenged. ("Yep, that there wire is definitely brown, Ha!").

At any rate, here's how my Anti-Dieseling Relay was wired. It's worth noting, I don't recall ever having the relay, and couldn't tell you the last time the A/C worked...................

Pink: Wire from IGN. UNFUSED on the fused box runs to the Anti-Dieseling relay. This is not correct for a pink wire on the Anti-Dieseling relay. Pink is supposed to run from the Anti-Dieseling relay to the Fan Switch.

Orange: Wire runs to the Anti-Dieseling relay from the BLOWER RELAY. The orange wire to the Blower Relay is plugged into CIG at the Fuse Box for power. This is correct.

Dark Green: Wire runs from the Anti-Dieseling Relay to the A/C Compressor Switch (button). This is correct.


In other terms, seems this anti-dieseling relay had two power sources (CIG and IGN UNFUSED). Additionally, I haven't a clue how it could have been wired to the fan switch, if at all. FUN!......But I do know how to get it right. The schematics are key.

Say, am I just missing it or don't the schematics in the assembly and service manuals cover the temperature system? I'm looking for a diagram similar the one you provided, only where I can read the colors as opposed "see" them. Thank you.

[gulfcoast66]

Some Great Information...