Testing ignition switch. Video inside. Is it dead?

[kcpope]

Welp, I'm currently trying to tune my engine, as some of you know from my other recent thread, but now I've got another issue that came up. That "for sale" sign is looking awfully tempting!!!

Was starting and tuning my car just two days ago, and the ignition switch was working fine (It's an aftermarket unit from Zcar depot BTW).

Went to start the car today to do more tuning, no crank. I hear the typical sound of a relay turning on in the passenger footwell, but no starter solenoid action.

No 12V power at the starter solenoid when the key is in the START position.

Used a remote starter trigger directly on the starter solenoid and she turned over and started up fine with the key in the ON position.

Now I'm checking my ignition switch. Please take a look at the video, and can I safely confirm the switch is bad?

 

 

 

[Captain Obvious]

I believe your assessment is correct. You should have power to that "S" terminal in the START position.

Have you tried wiggling the key around while you have the meter on that terminal? I mean, even if it's just intermittent, it needs to be replaced, but maybe you could confirm that there is connection there sometimes.

[kcpope]

1 hour ago, Captain Obvious said:

I believe your assessment is correct. You should have power to that "S" terminal in the START position.

Have you tried wiggling the key around while you have the meter on that terminal? I mean, even if it's just intermittent, it needs to be replaced, but maybe you could confirm that there is connection there sometimes.

Ok good.

Yes, tried all manor of finagling. Nothin. I have a supposedly higher quality switch from standard motor products arriving Weds, so we’ll see.

[kcpope]

To confirm it’s a faulty switch, I said to myself, well I’ll just jumper the wires on the plug that normally plugs into the back of the switch, thus confirming all my wiring between the switch and the starter is OK. Essentially “hot wiring” the car.

According to the factory wiring diagram, with the key in the START position I should have power at WR, GW, and BY. So I jumperd those 3 wires together, thinking it would crank the starter. Still nothing.

Any reasons this shouldn’t work?

[Yarb]

@SteveJ

[SteveJ]

49 minutes ago, kcpope said:

To confirm it’s a faulty switch, I said to myself, well I’ll just jumper the wires on the plug that normally plugs into the back of the switch, thus confirming all my wiring between the switch and the starter is OK. Essentially “hot wiring” the car.

According to the factory wiring diagram, with the key in the START position I should have power at WR, GW, and BY. So I jumperd those 3 wires together, thinking it would crank the starter. Still nothing.

Any reasons this shouldn’t work?

The key piece of missing information: What is the voltage to ground at the WR wire? 

If there is no voltage at the WR wire in a 240Z there are two primary causes:

1. The fusible link is bad.
2. The ammeter gauge is bad.

Does your horn work? Do your hazard lights work? Do your brake lights work? If the answer to all 3 are "no", then look at the fusible link.

Next: If the answer to any of those 3 is "yes", then do you have power at the cigarette lighter? Do your running lights work? Does the inspection light work? If none of those circuits work while you have hazards, horn, or brake lights, then it's quite possible the ammeter gauge is bad. (Note: I have seen a couple of real-life cases where the ammeter gauge blew because someone connected a battery backwards.)

 

[kcpope]

10 minutes ago, SteveJ said:

The key piece of missing information: What is the voltage to ground at the WR wire? 

If there is no voltage at the WR wire in a 240Z there are two primary causes:

1. The fusible link is bad.
2. The ammeter gauge is bad.

Does your horn work? Do your hazard lights work? Do your brake lights work? If the answer to all 3 are "no", then look at the fusible link.

Next: If the answer to any of those 3 is "yes", then do you have power at the cigarette lighter? Do your running lights work? Does the inspection light work? If none of those circuits work while you have hazards, horn, or brake lights, then it's quite possible the ammeter gauge is bad. (Note: I have seen a couple of real-life cases where the ammeter gauge blew because someone connected a battery backwards.)

 

Hi Steve, I was hoping you would chime in!

At the ignition switch plug, I have 12V from the WR to ground.

brake lights work, hazards work, running lights work, engine inspection light works. 

I don’t have a cigarette lighter or horns hooked up to test at the moment.

[SteveJ]

Year of car? Was it originally manual or automatic?

Please go here and click on the link to create a signature. https://www.classiczcars.com/settings/ Include information such as the year of your car and any known modifications. It helps a lot with troubleshooting.

[kcpope]

16 minutes ago, SteveJ said:

Year of car? Was it originally manual or automatic?

Please go here and click on the link to create a signature. https://www.classiczcars.com/settings/ Include information such as the year of your car and any known modifications. It helps a lot with troubleshooting.

Signature updated, thanks.

1972 240z with an L28 with SUs. Car was originally an auto, but I 4 speed manual swapped it. I jumpered the auto trans interlock wires together as described in other threads. I also have the firewall mounted "K18" relay mounted and plugged in next to the battery. And like I mentioned, it was cranking over and starting up just fine this past weekend.

 

Edited August 27, 2024 by kcpope

[SteveJ]

First check the jumper. Make sure it's still in place.

Next, you want to make sure you have continuity in your wiring harness between the ignition switch connector and the solenoid. You want to make sure the dash harness to engine harness connector is still connected firmly (and free of corrosion). This is the connector you are looking for:

You might have to get some help to test the entire length. One way of testing is to take the BY wire off the solenoid and make a jumper wire to ground it. Then see if you have continuity to ground at the ignition switch connector. I cheat. I have long enough leads to test wires from the front to back of my Zs.

[kcpope]

58 minutes ago, SteveJ said:

First check the jumper. Make sure it's still in place.

Next, you want to make sure you have continuity in your wiring harness between the ignition switch connector and the solenoid. You want to make sure the dash harness to engine harness connector is still connected firmly (and free of corrosion). This is the connector you are looking for:

You might have to get some help to test the entire length. One way of testing is to take the BY wire off the solenoid and make a jumper wire to ground it. Then see if you have continuity to ground at the ignition switch connector. I cheat. I have long enough leads to test wires from the front to back of my Zs.

Hi Steve,

Ok, followed your direction. See the following video and let me what you think. Also, didn't mention it in the video but the jumper wire for the auto trans interlock is still in place and functional.

 

 

 

[SteveJ]

Okay, I had to dig through the 73 wiring diagram. That looks like the K18 relay. If the relay has failed or lost its ground, then the car won't start. That's part of the nag warning for the seat belts. While it's present in the 72, the circuit didn't make it into the wiring diagrams.

You can get this connector from Vintage Connections (https://www.vintageconnections.com/products/6-3mm-connectors?variant=46131501236545) and make a nice, plug-in jumper.