Solved! Door switch and ignition buzzer relay
 

Hallelujah!
After searching, reading, and finding no one with the same issues as I had, I started a new thread (http://forums.pelicanparts.com/porsche-911-technical-forum/567246-ignition-seat-belt-buzzer-new-relay.html) but got ZERO responses. Ah well.

Anyway, here is the answer that I hope may help others down the road...

Problem:
The ignition buzzer wouldn't shut off. Easily solved by yanking the relay.
Simultaneously, or coincidentally, the over door lights stopped turning off with the doors closed.

Supposition:
The buzzer relay is connected to the over-door lights, and is activated (among other things) by the ground at the door jam switch. My theory is that the buzzer is meant to sound when one of the doors is opened, or not closed properly, to alert the driver. Hence, the connection from the door jam switch to the buzzer relay.

Vexing:
No one here was able to confirm this for me, and wiring diagrams are pretty confusing for non-electrical gurus such as myself. So, where's the problem? Is it one or both of the door jam switches? Is it the wiring at one or both of the switches, or up at the lights, or a short somewhere hidden? Or is there some connection with the buzzer relay?

Checked:
Both door jam switches looked fine, and were connected to the brown/ white ground wire. Neither looked corroded. Rubber covers looked good, too. Both light bulbs looked good, and all wiring and ground in each light looked good.

Solution:
Replace door jam switches ($12 each, bought from our host), replace rubber covers ($1.50 each, right here), replace washers. Clean areas with contact cleaner and use di-electric grease at the connections. Reinstall annoying buzzer relay.

Result:
Let there be light...when the doors open! Let the buzzer shut up... when the doors are closed! As new. Cost was minimal.

Again, hope that helps someone down the road.
CATTMAN

Wow. I guess it makes sense after the fact. Buzzer is activated to tell you key is in ignition (I am correct that the key has to be in the ignition for your problem to occur?) when you open the door. So it makes sense that the door switches would be a source of the problem. I believe the key has to be installed because that's where the buzzer is located- in the ignition column lockset assembly behind/under the dash.

With all due respect to your success, did you try to repair the old switches? I recently pulled a bunch of unneccessary electrical wiring stuff from my racecar and noticed these switches are a simple contact unit. So all you need to do is ensure the contacts are good and the switch body is cleanly grounded to the chassis?

Very good of you to share so others can learn from this. I too had an intermittant buzzer issue in my '87 and never bothered to fix the switches. I blindly replaced the buzzer and it didn't work any better........duh.

Correct, when the key is in the ignition, the relay (in slot 2 out of 3 behind the oil gauge) looks to see if:
-seatbelt is fastened
-doors are closed

If the seatbelt is fastened, and the doors are closed, the buzzer will shut off. It will also shutoff without the seatbelt fastened, but only after a few annoying seconds. HOWEVER: your buzzer will remain on, driving most owners to pull the relay, if it doesn't know the doors are closed! It relies on properly functioning door contact switches for that information.

So yes, all I had to do was replace both door contact switches, washers, and rubber covers.

Conclusion:
If either of your 2 door contact switches malfunction/ corrode/ become separated from their ground wire, your buzzer will stay on. Most likely you'll remove that relay, and in the process lose your auto on/off lights with door open/ close.

So if that sounds like you, try replacing both door contact switches, washers, etc. and put the relay back in place, and see if your buzzer shuts up, and your auto on/off interior lights return.

Really simple double win!
CATTMAN

Excellent, Cattman! I also pulled the relay/buzzer out from behind the speedo(or was it the tach?), and now my inside lights don't work.

Problem solved. Thanks so much.

I found the same problem in the past..where the door switches looked good, but after they were replaced ( in desperation)...all was back to normal. The switches are hard to check properly for continuity.

Here's another hint...at least for the 3.2's ... may apply to SC's and other cars. When you drive the car and then stop/shut off the engine, while still sitting in you car and *not* having opened the door..... you should be able to open/close the power windows and sunroof at will, many times. However, once the door is opened ( and then closed, car engine still "off")....the power to these circuits should have been killed and you no longer should be able to operate the sunroof and power windows. If you can....you have an energized circuit that shouldn't be energized any longer, and this will have a high curent drain on your battery. Culprit?---> the door switches.

I pulled the annoying buzzer within a few days of ownership, this little black relay still sits in my tool box. Interestingly, my interior lights still operate on/off with doors opening & closing.

Thanks for the tip on the door switches.

Then yours must be wired differently than mine. Interesting, I will be interested in researching that.

Hi,
Nice that you got it working ok!
Could you post the part number on the "seat belt/key in ignition" relay? Mine is missing and I want the "fasten seatbelt" light to start working again as it is the last electrical "non working" item in the car.
Thanks
David

Sure, it's Part #: 911-618-102-00-M100, called the "Relay, Seatbelt Warning", sold here for $64.25.
Here's the link:
Pelican Parts - Product Information: 911-618-102-00-M100

CATTMAN

+1 for our '86.

Odd twist to similar problem
 

I have an odd twist to a similar problem and am looking for advice...

In my 87 Cab, my dome light and buzzers work fine when the light is set to illuminate with doors open. If I am in the car with doors closed and switch the dome light to "on", the door/key buzzer continues to buzz and the light will not illuminate. The only way to stop the buzzing is to switch the light to the illuminate-when-door-opens position.

Any thoughts about diagnosing this?

Thank you Cattman! I am having the exact same problem and I have been searching all over the forum for solution. just to confirm when you mentioned "door jam switch" you meant "door jamb switch, for interior light" right?

Will it be convenient if you can share the parts number?
Thx in advance!

Not a problem for my '88 either...

Nor my '87... In fact, I just got the seat belt relay this summer after 3 years of ownership. Lights always functioned properly.

P/N is 928 613 147 00 - door contact switch for interior light (from the '87-'89 PET).

I want my ‘86 Carrera to work like it did when new, including the intermittent annoying seatbelt/door buzzer.

I replaced both door switches (they activated interior lights beforehand, but I changed them anyway). The relay was removed, contacts cleaned, & relay replaced.

My buzzer & seatbelt lights are still intermittent.

Any other ideas?

It might be the ignition switch itself that's causing the intermittent operation. The switch is a multi-pin unit that attaches to the rear side of the ignition lock set. Over time it sees so many cycles of operation that the internal contacts can wear out.

Changed the 2 switches, replaced the relay, and still nothing. Looking like it may be ignition switch or elsewhere.

When I pulled the fuel/oil gauge, noticed 2 wires unconnected. One is brown (ground), and the other red with black stripe. Nowhere to plug them on that gauge.

Any ideas?

+1 on the +1, 1986 Coupe here. No buzzer, lights function fine...