Headlight/Tailight Issue

[gtrp]

Hello,

Decided to drive my 911 in the rain and after 30min into it, my headlights and taillights went out.

Is there a single source of failure that would cause both to go out? A common ground or fuse?

[seafeye]

If all the lights are out I'd first look at the light switch. I believe each tail light is on their own circuit. So check that you have power to the switch?
Also helpful to know what year of car you have.

[gtrp]

Thanks.

It is an '81sc


81' 911sc - Weekend Project Car
09 GTR - Race Car

[targa80]

There are schematics for the 81SC posted on this site under the parts catalogue web page.

There are several checks you can do to help isolate your issue.

1. With no key in the ignition if you pull back on the dimmer headlight/turn signal switch does your high beams flash on as long as you hold the switch back. They should and this would mean you have battery voltage at terminal (30) of the light switch. Also if you select the right or left turn signal position the parking lights should come on for the side selected.

If the high beams do not come on then your problems is the battery voltage at terminal (30) of the light switch which is supplied from terminal (30) on the ignition switch and the ignition switch is supplied from the battery.

If the above test works then:

2. With the ignition switch turned to on check for 12 volts at terminal (75) on the Light switch. If it is there then your failure is in the Light switch. If you do not have 12volts then check terminal (X) on the ignition switch. If the 12 Volts is there then you have a bad connection between the light switch and ignition switch.

If you do not have 12 volts at terminal (X) on the ignition switch then you have a problem at the ignition switch between terminal (X) and terminal (30).

[gtrp]

I appreciate that! Gonna give this a try tonight and see what I can find.

This car has been thru 1-2 sound systems and an old alarm system so the wiring is a mess from a previous owner.... Going to try to clean it up while I'm in there.




81' 911sc - Weekend Project Car
09 GTR - Race Car

[targa80]

Actually, that Rats Nest doesn't look too bad for a 33 year old car. Do you have a copy of the 81SC schematics?

[targa80]

I just noticed the added on ATO fuse block, Humm, that needs to be accounted for and compared to the schematics.

In my own case, I modified my panel to accept ATO fuses and it was a (FUN) experience doing the conversion and then doing continuity and power checks to make sure all was correct and matched the schematics. Granted, It is a job that requires a reasonable amount of technical skill related to testing and troubleshooting electrical circuits and the capability to understand the flow of electrical schematics. On my panel I added 5 additional fuse slots for expansion.

[gtrp]

I do not have the schematics yet but will search for it when I get home. My car didn't even come with a fuse box cover.

I was thinking about just converting it all like yours, just didn't think I'd start working on the electrical items during the winter. That looks so much better, I'm just a military man and know very little about electronics. How hard could it right? haha


81' 911sc - Weekend Project Car
09 GTR - Race Car

[porwolf]

Originally Posted by targa80

I just noticed the added on ATO fuse block, Humm, that needs to be accounted for and compared to the schematics.

In my own case, I modified my panel to accept ATO fuses and it was a (FUN) experience doing the conversion and then doing continuity and power checks to make sure all was correct and matched the schematics. Granted, It is a job that requires a reasonable amount of technical skill related to testing and troubleshooting electrical circuits and the capability to understand the flow of electrical schematics. On my panel I added 5 additional fuse slots for expansion.

Goo looking fuse conversion! What ATO fuse holders did you use?

[targa80]

The following link is from 2004 when I started my conversion to ATO fuses and I provided the part numbers and the supplier info. It should be noted that at that time, I was stripping the car for an off chassis restoration and all of the wiring was being removed.

Fuse panel upgrade to ATO type

In the 2004 time frame I labeled each wire removed from the old fuse holders and noted all jumpers on the back of each fuse block. I had to cut the openings on the fuse panel mounting frame to accommodate the ATO fuses. The fuses did clip into the opening and they did gang together. All of the wires do fit behind the mounting frame including the wires that I had made up to replace the fuse block jumpers. Also used shrink tubing to cover any of the male/female terminals used to make up the required jumpers.

In the summer of 2014, which is 10 years later, (what can I say, life got in the way until I retired). I finally got around to getting the wiring harnesses and the fuse panel back into the car. I performed a continuity test on each circuit and compared it to the 80SC schematics before applying any battery voltage. Next, with battery voltage, I added each circuit fuse and tested each circuit for proper operation.

In my case it was a time consuming process due to the length of time between removal and install. If I was only doing the ATO mod and not removing all of the wiring for the restoration it would have been a 2 to 4 day project.

By the way the thread above has other alternative ways of doing the same type of mod.

[gtrp]

Hello,
Finally got a chance from work.

So when I tried your test targa80, my high beams did not work with no key.

Signal left - nothing.

Signal right - headlights and taillights work.

Yikes


81' 911sc - Weekend Project Car
09 GTR - Race Car

[gtrp]

Actually when I signal right, even my high beams work.

With the keys in, left and right act appropriately. Hmm.


81' 911sc - Weekend Project Car
09 GTR - Race Car