Electrical Gremlin(s) - Must Fix Before Oct 2/3 DE
 

I previously posted in the Oct. 2/ 3 DE thread about a possible alternator problem. The "Seat Belt" light comes on for a few seconds here and there after driving the car for 10 - 15 minutes. When the AC is running, the fan sometimes surges. When driving during the Air and Space Museum/ Gainsville fun-run a couple weeks ago, the speedometer needle started jumping all around, usually for 4-5 seconds at a time.

This past Sunday, Dave Riley helped me try to track down the problem. We tested the voltage at the battery at both idle and 3000 rpms, and it was 13.8-13.9.

We started pulling the cables off the main grounding post, and the evaporator fan came on (while car was off, no key in ignition). We thought the fan may have been the problem, so to test that theory I cleaned the ground post and all five connectors, reattached everything to the post, and drove home with the fan "in the loop". After about 15 minutes, the Seat Belt light came on.

After I got home, I unplugged the fan connector. I drove the car to dinner a little while later, and the Seat Belt light came on again -- so the fan is not the problem.

The car is a stock '87 911 Targa, and the only electrical mods I know about are for the Alpine head unit and separate amp Vu installed for me at a Dorki get-together well over a year ago.

Any ideas/ suggestions? I was just accepted for the Oct. 2/3 DE (off the waitlist), so I need to be confident I can get this fixed within the next week -- even if that means replacing the alternator (which I would need Dorki-help for). There were previous suggestions for testing the alternator with an o'scope, but I do not fell confident the car will make it from Alexandria to Great Falls and back, and I reallly don't want to get stranded on the Beltway or GW Parkway.

**late addition - The alternator light comes on when the car is started.

TIA,

After spending some time digging through the Bentley manual, it looks like the Seat Belt warning light and speedometer share Ground 116, which is located up near the brake master cylinder.... I need to clean this one up before heading to work tomorrow morning and see if that helps. I have my fingers crossed...

While not nearly as technical as putting on voltage meters etc... I find a piece of black electrical tape should cover that seatbelt warning light pretty well :wink:

Let us know how Ground 116 works out as it does sound a bit more effective than my approach.

Well the 116 ground had nice, bright metal at the contact area. I sanded the sheet metal and cable terminal anyway -- just for kicks. I went out driving on the Beltway and 395 for a while, and the Seat Belt light came on again after about 15 minutes. Anyway, the headlights and dash lights don't dim, and I am feeling more and more like this problem will not result in a dead car at the track. Therefore I have accepted the open slot in Blue for the DE, and I will see everyone in the paddock!

Does anyone have an extra oil filter and crush washers I could buy on Saturday? I would like to change the oil at Tischer, but all I have so far is a case of Redline...

I'd bet good money you have a bad voltage regulator. I had one, and the symptoms were the same (except the surging A/C - its hard to surge when your in a box on a shelf). The Seat Belt Warning light seems to be a common problem - it lights up when the voltage goes to high. I'm not sure why. Put a volt meter in the car for a while and watch it. Its an intermittent problem, so having a gauge to look at when the problem occurs is key. My guess is you're getting about 17V on the surge. This is a common problem on Carreras and fixed by a new $50 VR.

If you are having an overvoltage issues, get it fixed ASAP before you overcharge and boil your battery, spewing sulfuric acid all over your trunk. Don't just cover the light with electrical tape :D .

I got to go with the Alt or Reg. Grounds tend to keep things from working not working when they are not to.

New Reg is cheap insurance and they are inexpensive enough to just change out. This is where I would start.

Alt can be cleaned and rebuilt depending on what is bad. Brushes and bearings are easy to replace.

I had an old truck that had a high beam light that came on from time to time for no reason. The truck was not worth the time and parts to find and fix so I just took the ofending bulb out of its socket. Funny thing, that made oncoming drivers flash their lights at me. How did they know? :roll:

What Kurt said.

The brushes are very easy to replace as they are part of the VR. When you put in a new VR, you get a new set of brushes. I personally would start with a VR and keep a volt gauge mounted in the car somewhere to monitor the system. I replaced my clock with one.

Oops. Thanks for the tip in. I forget that some of you guys have modern cars. some of us folks with the olden kind have the reg sitting off to the side. You can open it up and ajust it too. "Wow look how bright the lights are now!"

Does replacing the internal VR require removing the alternator from the car? If so, would a fellow Dorki be willing to help with the installation one night after work next week?

Also, are there any misc. bits and pieces that need to be purchased, or just the VR? TIA,

Yes, it does require removing the alternator. I've done it before and don't mind helping you you feel like humping all the way out to Germantown. All you should need is the VR, and maybe a new alternator blet if the current one is getting a little long in the tooth.