Where would you start looking? (Electrical issue)

[mark '87 930]

First let me start off with what i thought was a Speedo problem...

A few months ago, my speedometer starting acting up and wasn't always working. The lights would stay on for that gauge, but the needle would not budge, nor would the odometer. When I went over bumps, it would start working again and then stop.. so it was intermittent, and I thought it would be a connection somewhere. I never really checked it though.

Today, everything was working fine and as I was driving home (it was raining a little so I had the wipers on), as soon as I turned on my lights, the Speedo went dead again, and my wipers were erratic.

So now I know it's a power/connection issue somewhere. I'm sure something is getting hot somewhere!!

I checked my voltage at my battery with the car running and revving.. I never saw anything over 13.5 as I revved it, but i only checked for a few blips of the throttle. It certainly wasn't erratic which is good.


I also checked all my fuses and a few connections in the front area that I could reach. Nothing out of the ordinary, and I used some die-electric grease as well just to be sure..

Where would you start to look?

[p911dad]

I would start with the ground points. There is one just behind the tach(access thru the trunk)with several brown wires held down with a nut, and several others scattered around the car. Clean the wires and post and reattach. Good luck.

[dshepp806]

wonder if a cap's going bad on the odo board>? bringing down the DC buss a bit (just before it shorts!) First, it sounded like a bad gear issue..but now it seems different with the electrical symptoms (double whammy? hope not..)

alt/reg good?

Best,

[Superman]

There is almost nothing better you can do to an older car than to disconnect, clean and reconnect electrical connections. All of them. Including and especially the grounds. And the big connections at the battery. I don't know how many times folks have assured me their battery connections were fine, before I solved the problem by cleaning them.

[mark '87 930]

I will check the grounds starting with the one near the tach.

I took it out again tonight and have always noticed (since I got the car 2 years ago) that my speedo is significantly dimmer than the rest of the gauges (WAY dimmer). I changed the bulbs in the gauge thinking that was it, but never did anything. that said, I now doubt there is anything wrong with the speedo itself.

I checked/cleaned both battery terminals and where the ground strap ties into the body. My battery is new from the spring, and I didnt' see anything unusual there.

If only the speedo is dim (again.. really dim) compared to the rest of the gauges, I get the feeling it's just not getting enough power somehow. I'll check the wiring diagrams and the car at the same time. Will report back.

[Hetmann]

I was confounded by an electrical issue with my SC. Coincidentally I replaced the electrical portion of my ignition switch because of starting issues. I retained the mechanical portion. Anyway, the speedo, lights, sunroof etc would sometimes quit and other times work fine. Turns out my ignition switch was not returning completely to the "run" position from the "start" position whenever I started the car. It sort of went somewhere between the two. I now know to put it in the run position. My Porsche technician tells me he has a part to repair this. I will be looking into that next visit. Its a long shot, but check that you ignition switch is in the right position while you are driving around.

[mark '87 930]

HOW DA F$%^ do you get to the back of the gauges from the trunk area?

The only way I see if removing the tach and fishing around with my hand from the cockpit. I can't even see a ground connection around there with a flashlight!! any clues?

In looking in the wiring diagram, the ground for the speedo goes to what looks to be "VS XV"? the grounds start with MP.. so what does VS mean?

[Brian 162]

My SC has been doing the same thing recently. If I tap the speedo while driving it usually comes back to life. I've had the gauges out and cleaned the connections and it seemed to help. The easiest way to gain acess to the wiring is to remove the gauges otherwise you have to remove the blower motor and ducting from the trunk area.

[mark '87 930]

Yeah, I had my speedo and tach out yesterday and the connectors were all clean. I even added die-electric grease to see if that would help, but still the same. I couldn't find a ground point back there, but the manual states there is on in the middle of the carr somewhere. I'll keep trying.

Thanks for all the advice, keep it comin'.

[DonDavis]

Originally Posted by mark '87 930

HOW DA F$%^ do you get to the back of the gauges from the trunk area?

You don't. You said it too, They have to be removed from inside. Sounds like a pain but it's easier than going in from the behind. Warren aka "Early S Man" has a liquid solution he uses to clean electrical contacts. If you use an abrasive and remove metal,you're just setting yourself up for more problems in the future. Clean gently and insure the connection is tight. Lots of problems can be traced to loose connections. Not necessarily dirty contacts. So take a good look at the contacts. Clean with a soft cloth and alcohol.

[mark '87 930]

got it all sorted out.. so I figured I'd 'close this thread off'.

It wasn't wired properly (strange how it worked awhile ago though). There are more prongs/tabs on the gauge than there are wires that connect to them, so I checked it against someone elses. My lights are as bright as the other gauges now, and the speedo works regardless of my lights being on or off (that was a weird thing I tell ya!!)

Thanks all for your help.