Car stays running if headlight switch is on

[bobmagyar]

My car has developed a "Feature" that I would like to rectify.

When the headlight switch is in the driving lights or headlights on position the engine will continue to run when the ignition is turned off. Everything else otherwise works completely normal.

Would anyone have an idea what to consider when troubleshooting this?

Thanks in advance!

Bob

[Scott A]

The only thing I can think of is:

1. A wire from key switch got plugged into the light switch. Which is close.
2. The wires (pins) in the 14 pin, in the engine area got swapped around.
(As some of these wires give engine power)
And they often melt too. And touch another pin.
3. Headlight wires. Near the switch can get real hot. And melt. And short.
(especially if you don't have headlight relay)

Do the lights have to be "on", to start the car?

[bobmagyar]

Thanks for chiming in.

The lights do not need to be on for the car to run correctly.

I cant rule out any of the options without digging into it. I have to say I really dislike working on the wiring in that area. It is so frustratingly tight.

[Arne]

I'd focus on the gauges and dash illumination lights. I suspect one of the gauges or the gauge lights is cross-connected somehow.

[edmayo]

Since we can assume the car didn't always do this what was the last thing done before this occurred?

[Scott A]

As I think about it more.
There might be a hot wire that is shared between key switch and headlights switch.
Normally. The key has to be on for headlights to go.

I think your going to find that your headlight switch melted or fused, inside, in a small area.

Yes. It is a tight. Terrible area to work in.

I think. In the end. You'll have to find a working headlight switch. And swap it out. And see what happens.
But go slow. Disconnect battery. And double check where your putting the wires.

So. If you start the car. With the lights off. Can you turn the key off, and car goes off?
But, with car running, if you turn your headlights on. Turn the key off. The engine keeps running?

[NorthernThrux]

If your car keeps running, it means that the CDI is still receiving power when the ignition switch is off. Fuse 8 (of 10) on a 73, not sure about 70. That is the only way the car can still be running. But if you trace back why that circuit still has power when the ignition is off, you’ll probably find the clue. And you can do some of that tracing in the frunk, which is far more pleasant than squirming under the dash. Check if the CDI gets power when you turn on the headlights (ignition off). This will be a clue. Pull the CDI fuse when the car is running after you turn off the ignition and the headlights are on and see what happens.

Is it the headlights only or the parking lights as well? If the former, you can at least eliminate the 14 pin connector at the back.

[bobmagyar]

Thanks to you all for your replies. All of them are will assist me in tracking this down.

I will speak to a few points from the various replies.

The good news is I have a spare headlight switch. Sorry Kenik I think I need to hang on to it now.

With the headlight switch off the car starts and turns off completely normally.

It seem like the light switch is powering the CDI and that seems easy enough to verify.

I will unfortunately not dive into solving this for a month. My Westfalia just ate its engine, and in the Covid Era, I really need to get that sorted first.

[stephers]

I had one once that did the similar thing, the owner replaced the small 3 fuse block in the engine compartment with another one that he had purchased but it was the wrong year and was fused so that power was going to the CDI box when it was not suppose to Changed to the right one and all was good

[dogLeg]

I had this exact (bizarre) issue on my 70T when I first got it. I would pull in somewhere with the lights and ignition on and turn the key to the OFF position and the car would keep running until I turned off the lights. This was very early days after I got my car and it was one of many haywire electrical issues that I was experiencing. I had chaotic turn signal/brake lights/hazard/wiper/instruments - you name it.. prior to my ownership the car had been mostly sitting. After a deep cleaning on the front & rear fuse panels (with some corrosion X & wire brush) and ground wires (and for me extensive cleaning of connections at the turn signal/lights & grounds) all of these issues were resolved. I did later replace my CDI, but the unit itself was not the issue, I never touched the ignition. I would start with double checking & cleaning all front fuse panel connections & related grounds - as its the easiest.