Recently purchased a 1983 928S and have not yet been able to acquire the workshop manuals. I have a couple of very annoying electrical problems that I am hopeful someone can help me with. My headlights are currently headdarks, the relay clicks when I change from low to high beam, but there is no voltage at the connectors on the lights themselves. The lights are good. Can someone advise me where a ground connector or other connector might be located that is the culprit. Also my brake lights never come on either. I suspect the switch on the pedal, other thoughts anyone? What is the easiest way to access the switch? Thanks in advance.

Mitch Johnson
83 928S US

 

Mitch -

First of all - welcome to the wonderful world of sharks!

The VERY FIRST things to do - (This is a cut and paste from posts by Wally P. @ 928 Specialists...) These simple steps - about 2-3 hours worth of work)will fix MANY of the electrical problems you have (and some you DIDN'T KNOW you had!).

(THANKS WALLY!)Annual maintenance:
1) Open the hatch and remove the tool panel. Remove the carpet and spare tire cover. Remove the spare, tools, etc. Open the battery box.
2) Disconnect the ground cable from the chassis. Remove the negative battery terminal. Remove the positive battery terminal. Remove the battery. Use extreme caution to avoid getting battery acid or residue from the top of the battery or cables in your eyes. Goggles are recommended. If the battery brushes against your clothes, you can end up with holes.
3) Clean the battery terminals until they are bright and shiny. Dull gray won't do. If it is possible to check the fluid level in the battery, do so. Fill to the rings. Wash the battery. Put it on a charger if possible.
4) Clean the battery box, removing all corrosion. Wash the battery box. After it dries, touch up the finish as required.
5) Clean the battery cable terminals (all three) until the connection area is clean and shiny. Dull gray won't do. Clean the connection area on the chassis.
6) Clean the speedometer/odometer drive electrical connector in the right forward corner of the spare tire well (pre-'90 models).
7) Raise the hood (bonnet). Remove the protective cap from the jump start terminal and pull the protective plastic cover from the terminal. If you are missing the cover or the cap, replace them - they are critical items. If there is no cover, water will enter the connector and corrode the connectors and wires, causing serious electrical problems.
8) If the connections are clean and tight, replace the cover and cap. If the connections show any corrosion or looseness, disassemble, clean and reassemble.
9) Jack the right front of the car so that you can SAFELY work underneath.
10) Remove the ground cable that runs from the right side of the engine to the chassis. Clean both ends of the cable, and check for corrosion in the cable. Clean the connection points, and replace the cable.
11) Check the heavy cable connection on the starter solenoid for looseness or corrosion.
12) Check the moderately heavy wires on the same connection for corrosion and breaks inside the insulation. These carry the charging current from the alternator.
13) Check the small yellow wire connection for corrosion and tightness. This wire triggers the starter solenoid.
14) Lower the car. Fold back the carpet and open the central power panel cover.
15) Check the main power connections at the top of the panel for tightness and corrosion.
16) Check the ground connections above the panel for tightness and corrosion.
17) If you are having electrical problems, remove each fuse and reinsert three times. Check the fuses for the proper value, and examine them visually for damage or corrosion. Test them if desired. Later cars have a fuse tester built into one of the relays.
18) If you feel that it is necessary, remove and reinsert each relay. This won't be easy, as they fit very tightly in some cases. Porsche sells a relay removal tool, but I am not impressed. It is basically a pair of pliers with square jaws, and will pull the relay apart. One tool that works well is a spark plug boot removal tool. It is a thin but strong sheet metal tool shaped like a "J" with the top 1/8" bent over at a right angle. You can put this angle under the bottom edge of the relay and lift it out - IF the battery is disconnected!
19) Close the panel and replace the carpet.
20) Replace the battery. Install the positive cable. Install the negative cable. Put a drop of oil on each nut. Connect the chassis end of the ground (negative) cable. Lubricate the battery box latch and close the box.
21) Lubricate the wiper drive shaft and hatch latch mechanism.
22) Clean the spare tire, jack and tools. Put a couple of large heavy plastic garbage bags in the spare tire well for emergencies, along with a tube of hand cleaner and some paper towels. Install the cover and carpet.
23) Lubricate the jack, and put it inside the tool panel. Clean and lubricate the tools. Reinstall the tool and tool panel.
24) Reset the clock and radio presets.

 

Mark

Thanks for the welcome! I have already planned the electrical PM in your post, thanks.

Anyone know of a way to test relays besides R&R? Is it safe to assume if the relay makes a clicking sound when it should, that the relay is in fact ok?

Another sideline....Cruise Control - mine doesn't work, advice on where to begin troubleshooting it and common failures associated with it would be most appreciated. Damn I wish those workshop manuals would get here.

Thanks everyone.

Mitch Johnson
83 928S 5sp Black

 

Mitch,
Willkommen.
One of the Big Three 928 suppliers -Devek,I think-has a fuse and relay chart on thier site.
Start back at the home page and find Rennlist supporters,then go to the Devek site.
See if there is another relay that you can swap out. You know, just pull out of one slot and plug it in the headlight relay slot.
Also check the Greg Nichols Site:
http:// <a href="http://www.nichols.nu/tips.com" target="_blank">www.nichols.nu/tips.com</a>
Also check the Rennlist archives using the search feature at the top of the forum page. If you have a owners manual the fuse/relay diagram should be in it.
You might have a light switch problem as well.
Do you have a master caution (!), or dash pod warning on those tail lights? Do you have side marker and running lights? If any of these are out recheck the fuses, then pull the tailight lens and check bulbs and sockets.
The cruise:
Check above mentioned sites and start getting familiar with your vacuum lines. the is a semi-helpful diagram under the front of your hood.
Arbeit machts du frie.
John S. 82' Weissach, auto 'Pattycakes'
<img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />

 

The High and low beams are on different circuits and fuses. Clean all the fuse connections at the fuse panel. Could be the answer to the brake light problem too. Welcome to the 928 Electrical Gremlin Club.

Anthony Tate
79/928 Silver Metallic

 

John,
I have no master caution or dash pod warnings on the brake lights and all of the other lights work fine. I will do the fuse swap and connector cleaning and hope that does the trick.

A vacuum problem was my first thought on the cruise, I do have an erratic idle when the engine is hot which I deduced to be a vacuum leak. thanks for the help, I'll have to work on it next week and will let you all know how it comes out.

Anthony,
It seems that the fuse connector cleaning is the common theme and I will take care of it next week. Thanks for the assistance.

Mitch Johnson
83 928S 5sp Black

 

Congratulations on acquiring your 928! There are few vehicles that will put that big a grin on your face. You can expect a few months of slowly finding and curing the PO (Previous Owner) problems, but the pleasure should greatly outweigh the pain. If it gets bad, just do the same thing that married people do - just relax and pretend that you are enjoying it.

HEADLAMPS
Does the high beam indicaor on the dsh work? If so, the problem is usually the fuses or a connection. If not, the problem is usually the relay or a connection.

The relay charts are on our web page at
<a href="http://www.928gt.com" target="_blank">www.928gt.com</a>
along with other helpful technical info. There is no substitute relay for the double headlamp relay (XIX - XX) in the Central Power Panel. The headlamp relay, P/N 928.618.107.02, is unfortunately one of the most expensive ones, at $80.70. Make sure that you really need one! Let us know if you need more test info.

BRAKE LIGHTS

You have no brake light switch on the pedal. On your car, the brake light switches do double duty. In addition to the usual brake light operation, they also serve as the brake system hydraulic failure warning system. The hydraulic system is divided into two equal systems. There is a pressure-operated switch in each system, located on the bottom of the master cylinder. If both switches operate simultaneously, you get brake lights. If only one switch operates, you get both brake lights and a brake failure warning light.

In your case, carefully check fuse #7 and its connections. It serves both the brake light circuit and the lamp control unit that warns of brake light failure. This looks like the most likely problem.

 

You have no voltage at the connecters, or accrost the connecters?

Basicly, if power getting to your head lamps, and unable to get out, or not even getting to your headlamps?

It's not safe to assume that since the relay clicks, it works. The relay has two nearly independent circuts. One is the coil, it produced the magnatism to activate the switch, the other is the switch.

If the relay clicks, then the coil works, but the switch part may or may not make good contact. Only way I know of to test this is get a 12V power source, and a diagram of the relay. Find the plugs for the coil, put 12V accrost it, and see if the switch creates a closed circut accrost it's plugs.

If your problem is no power to the headarks, then it's somewhere in the connections, fuses, and relays. However, if you have power to the head darks, then I'd check the ground. This is a safe thing to do anyways, just for good measure. On the 83, there are 2 grounds on the frount cross member, infrount of the radator, on the side of the cross member closest to the radator.

One is pretty high up, and on the driver's side, the other is lower and on the passanger's side. The driver's side is pretty easy. The passanger's side is hard to see, because it's under the wireing harnass, and if you've got the a/c, it's a real pain to get to.

Good luck.

 

Wally

Great to hear from 928 Specialists, I peruse your site often, in fact it is my first reference for fuse/relay problems. Thanks for the info on the brake switches.

The high beam indicator in the dash does not work. I hate to change out the relay unless I can be certain that is the problem. I plan on doing a search and destroy mission on the connectors, though I am reluctant to pull the pod :-O unless I know the problem lies in there.

It appears the consensus is that fuses/relays or connectors are the culprit, no warning lights for either problem has ever appeared. I do get intermittent "Tail Lamp" warnings, bulbs check out fine and work.

PO had the car 12 years and managed to put 5,000 miles on it. It suffers from lack of attention more than anything. Garage queen (for lack of a better term) though stored outside under a carport.

I'm out of town for a few days and will be unable to respond until thursday or so.

Mitch Johnson
83 928S Black MT

 

ViribusUnits

The power does not get to the headlights all other functions of the headlight switch funtion correctly. I'll check the ground and after doing some maintenance on the fuse panel I may have to pull the instrument pod and lokk in there.

Thanks for the assistance.

Mitch Johnson
83 928S US Black MT

 

With the ignition on, headlights on, dimmer lever in the high-beam position, test for 12 vdc at the input side of fuses #24, 25, 26 and 27. If there is no power, move the dimmer lever to the low-beam position, listening for a click as you do so. If there is a click and the low beams then come on, the problem is the relay or a connection behind the panel, probably the relay.

As mentioned by ViribusUnits, you can test the relay. Remove the relay. Apply a ground ( - 12 vdc) to terminal 31, and apply power ( + 12 vdc) to terminal 86 (not 86M). The relay should click.

With no power on these terminals, there should be continuity between terminals 30 and 56b. With power, there should be continuity between terminals 30 and 56a.

While I can't recommend this, some folks have reported that you can clean the relay contacts by removing the cover. If you try this, remember that it will get dark pretty quickly if the relay fails again.

 

I get back from my trip and get in the car....magically the brake lights now work (haven't tried it this morning yet). Turning on the headlights causes a rather large voltage drop according to the dash meter (about 2 volts), is this normal or indicative of a short?

Wally thanks for the detailed info on the relay etc. today is the day to deal with the fuse panel so I will let you all know how it turns out.

 

Intermittent brake lights ( no brake lights with ignition off ever?) no luck on the headlights though I wasn't able to test the relay just yet....damn weather!. I give up for now, when I get the manuals I will tackle it.

Thanks to all that provided help.

 

Headlights now work, ground connector seems to have been the likely suspect. I didn't try to get at the one on the passenger side behind the A/C, I'll save that one for when I do the R134a conversion.

When I pulled the headlight relay, a couple of the connectors appeared to be "burnt" like they had arced or something. I have a new relay on the way but should I be concerned about this?

Thanks for the assistance.