Close Call! Electrical Issues

[FlyingDutchmann]

Hey all,

I've already shared with this group that I recently purchased an 87 Carrera Targa! Yesterday I had my maiden voyage from LA, where I bought it, to my home in San Francisco. On the drive I started to see all the things I need to work on. I think the car has great bones but could use a refresh with some of the details.

I noticed the driver side lock seems to only work if I use the wheel. It does not work with the key or the lock button on the center console. The passenger side mirror does not move with the electric toggle. And a lot of the plastic/rubber parts could use a refresh. The car was also lowered TOO low so will need to have that adjusted.

The strangest thing that happened was with the headlights. I was cruising on the highway as the sun starting going down and so I pulled back on the headlight knob to turn them on. As soon as I did that the car completely shut off. I had to quickly put my foot on the clutch and restart the car with my key. I stupidly tried this again while on the highway and the same thing happened. I have to say it was extremely scary. I had an 18 wheeler right on my tail. After turning off an exit and trying it while parked, the headlights came on no problem and I didn't have that problem for the rest of the trip. I'm curious if anyone has ever experienced this? In any case I'll likely take the car in to do all the above work.

[boyt911sc]

Find someone who could make the ghosts go away. This is the reason why you got a good price for your new car. Just kidding. Maybe you were just too excited to bring home a 911?

Tony

[Jd21476]

The key in your door will only work if the door is closed. I thought my key lock was broken as well and then read a post about how it only works closed. I tried it and it works fine.

[Ctopher]

Originally Posted by Jd21476

The key in your door will only work if the door is closed. I thought my key lock was broken as well and then read a post about how it only works closed. I tried it and it works fine.

Or the door lock operating rod is broken. My 87 passenger had the plastic ball socket broken, the new style is simpler and easy to replace.

Part# 964-537-571-00-M100


CTopher

[GH85Carrera]

There are many possible reasons why the car died with the headlight on. My first wild ass guess is the battery is low on charge, or the alternator is not charging properly.

The stalk that controls high beams is a weak design. The headlights needs a relay to keep that switch from frying itself.

Do lots of searches on the site for headlights and car dies. There are hundreds of posts. Someone has had your issue, and posted a solution.

Check all the grounds. Every one of them. Clean them up, and that can cure a lot of issues.

[pmax]

Turning on the headlights kills the ignition, no, haven't experienced it before. At highway speeds, seems unlikely the alternator and battery are both dead but who knows. Probably good to check out the electrical system and see what's going on .. custom wiring, alarm etc.

[Walt Fricke]

Not likely to be a basic alternator failure, or voltage regulator failure, or battery failure. If the alternator or VR had failed you would not have been able to complete the trip, especially not in the dark.

I'd purchase the kind of volt meter which plugs into the cigarette lighter, though. That way you can keep an eye on the battery/charging system.

As others have noted, it would be a good idea to undo and clean the battery to chassis ground, and the transmission to chassis ground. Another possibility is some corrosion in the crimp of the battery positive cable. Possibly, one of these connections (plus where the positive and ground attach to the battery itself)is a bit loose or has some insulating corrosion. Hard to see why the added current load of the headlights dropped the voltage to the ECU below what it could handle.

Another possibility is the fabled DME relay. It would be a good idea, as a new owner, to buy a new one of these, and install it. The original design of this relay was poor - the circuit board was cantilevered horizontally from some of the pins. The weight of the stuff on the board, plus the car bouncing and vibrating, would eventually cause a solder joint to fail, and the car to stop. You can prevent this by putting some insulating stuff under the circuit board so it can't flex up and down, unless the design has been improved. Guys could see, with a magnifying glass and ohmmeter, where the solder had cracked, and just resolder things.

The cylinder head temperature sensor can fail, but I don't think that would stop a running motor - more often it makes the car hard to start. I think by the time your car was made Porsche had to some extent fixed this?

There are two sensors which read the position of the flywheel/crankshaft, and are key to the engine operating. These can fail, and can be replaced. Possible, I suppose, that there is an intermittent issue with a connection.

I'd be sure to get a schematic of your car's electrical system, and dope out where various connectors are for these key systems. and then maybe find the connectors, disconnect and clean, and reconnect.

And with luck someone who has had issues like this will pipe up. Our '84 once stopped working right on the highway. Stopping usually allowed it to get going again, and we eventually got home. Despite what I said above, replacing the CHT resolved the issue. But yours, after the hiccough, worked fine afterward.

Grounds and power connections are standard things to work on no matter what on cars as old as these.