Looking for Advice on Early 911 Electrical Issues

[BlueSideUp]

I have a 1970 911T that needs a little electrical TLC. I’ll list off the issues and would appreciate any help you guys can give….

First the specs…

Dual 360CCA Batteries with clean electrical poles and terminals

Rebuilt Bosch 55A alternator (0 miles)

New Bosch voltage regulator from Pelican

Bosch distributor with clean points (the new points bought from Pelican were incorrect for my car). It is possible my car originally had a Marelli distributor and a later version was installed.

Clean alternator ground strap.

0.2 Ohms resistance measured between engine case and chassis

H4 sealed beam replacements, not the European H4s (someday) but the ones that replace the sealed beam lights in the sugarscoops.

And now the various issues….

1. The measured voltage at the cigarette lighter with the car off is 11.8V. The car sat for about a month while the alternator was rebuilt and various other projects progressed. The voltage with the car at idle is 12.5V and a 1500RPM the voltage is 13.5V. The voltage returns to 12.5V when the engine comes back to idle so it doesn’t seem to be an issue of exciting the field. After 1500RPM the voltage does not change. Should I be concerned about the slightly low voltage? Should an early car with a 55A alternator be able to produce 14V at idle?

2. The headlight switch has the classic problem of unintended high beams. I have read through the various threads regarding the simple repair to fix this problem. My car seems to have an issue that may or may not be related to the common switch failure. With the headlights in low beam (no blue light on the tach), the left headlight has the low beam lit and the right headlight has the high beam lit. When I go to high beam they switch, left low and right high. I can do a pretty cool patrol car impression with it like this but I’d rather have normal headlights!

3. I have a Nardi Personal steering wheel, can I just undo the allen bolts and remove the wheel to do the headlight switch repair or do I have to remove the adapter as well? I understand the main concern is getting access to the plastic cover.

4. The original issue that tipped me off to a voltage problem was a bouncing tach. Even though I have replaced the VR and had the alternator rebuilt I still have a bouncing tach. My original tach went missing somewhere because I have what I believe is a SC tach in my car (with the black centered needle). The voltage is steady (if a bit low). I would really like to find a correct tach for my car with the silver centered needle but does this sound like a tach problem? Should I try a different tach if I can find one? I bought a new transmission ground strap but haven’t installed it yet. My current one passes a visual inspection, the resistance between the case and chassis is very low. The only possible issue with the strap could be a loss of connection being exacerbated by high rpm vibration.

My distributor



What arrived in the mail



The points on my car are a two piece affair while the parts sent in the tune up kit are a single piece setup. My brother gave me the same single piece points that he never used on his '71 S.

5. The passenger side parking lights seem to be intermittent. I played around with the fuses in the lower fuse box and was able to get them to come on for a bit. Unfortunately my car is missing the label on the inside of the lower fuse box so I don’t know which is which except for a fuzzy picture in the owners manual. I am going to try cleaning up the connections in the fuse box with a little sandpaper, is there a better way to get rid of the corrosion and prevent it?

6. My wipers are very very slow. I moved the stalk up and down through it’s travel several times attempting to see if it was corrosion in the switch with no effect. I understand there is also a ground behind the clock that may need to be cleaned up. I am considering removing the blower motor to get better access to the assembly since I’m sure it needs to be lubed. From other posts on the board it doesn’t look like a whole lot of fun to remove the blower assembly. Just in case cleaning up the connections does not work, have any of you had the wiper motor rebuilt?

Thank you all for your help. I am finally getting some things sorted with my car and this website has been great!

Oh and just a couple random questions….

1. Are OEM Konis adjustable? Mine were recently replaced and my previous car was on coilovers with adjustable Konis (not the external knob type, push the piston in and turn).
2. Where is the switch for the trunk light supposed to be located? I have the light but it’s not connected and I can’t find the switch.

[304065]

Measured voltage at 11.8v= bad battery. Charge battery for THREE DAYS nonstop, measure voltage. Should be around 12.5-6V for full charge. That's the genesis of all problems. An early car should produce 14V at just off idle. Since it's still an external regulator, you probably have a 2W bulb for the warning lamp. Clean the warning lamp bulb holder contacts, clean the voltage regulator plug (be careful, they are fragile) and clean pin #11 of the 14-pin connector: perhaps corrosion is causing a high resistance condition resulting in the voltage drop, but more likely, your poor alternator is trying to bring a battery back from the dead.

One high beam and one low means someone has monkeyed up the wiring. Get out the factory diagram, you can download it here, and trace out all the wiring. Someone has probably mixed things up at the fuse box.

I did the flasher switch in my Carerra and I don't remember removing the wheel. Try just removing the clamshell first.

Bouncy tach= bouncing voltage. Fix problem #1 before spending ANY money on diagnosis of tach problems.

AKTUNG! You have a "cast-iron" distributor off a 64-67 911! You can tell by the cast-iron body, the oil cup, and the two-piece points. Wrong advance curve for a 911T. You need the Bosch for the T, these have an aluminum body, use single-piece points and take a later cap. Your cap probably doesn't fit very well, right? It's because the white thing, the insulator for the points wire, is hitting it.

If you decide to sell that old distributor send me a PM, I need a few for parts for my '66.

Intermittne parking lights. The fuse box order is on the wiring diagram. Carefully mark the wires and where they go before you disconnect anything. Electronics cleaner is a good first step, an ink eraser next, then escalate to fine emery cloth. There are a few good corrosion products out there, I like corrosion-x, an aviation product.

Slow wipers are a symptom of your low voltage. If the battery measures 12.5 static, perhaps it's your starter terminal, where the battery cable joins the cables from the alternator.

Trunk light switch is on the starboard side of the trunk, mounted to the CAR under the hinge.

Konis? I'm a Bilstein guy. Good luck!

[BlueSideUp]

John- Thank you for all the help. I will put the batteries on the charger for a couple days to see if that helps the situation.

Why are there separate fuses for the left and right headlights but only one of each is used for the wiring?

I will download the wiring diagram today and look it over. I won't be returning home until late tomorrow night so the diagnosis will have to wait until early in the week.

Thank you for pointing out the distributor issue! I was wondering why my distributor cap didn't fit too well. If you know someone with a proper distributor for my T I'd love to get the correct one in there. Obviously the 64-67 distributor isn't the best thing for my car, who knows if it has been recurved.

It seems I am missing the trunk light switch, it's low on the priority list right now but I'll have to get that figured out at some point.

[HarryD]

Originally posted by BlueSideUp
John- Thank you for all the help. I will put the batteries on the charger for a couple days to see if that helps the situation.

Why are there separate fuses for the left and right headlights but only one of each is used for the wiring?

One fuse for EACH part of the head lamp (left low, right low, left high, right high).

I will download the wiring diagram today and look it over. I won't be returning home until late tomorrow night so the diagnosis will have to wait until early in the week.

Good!

I did the flasher switch in my Carerra and I don't remember removing the wheel. Try just removing the clamshell first.

You will need to remove the wheel as several of the mounts for the clamshell are behind the wheel and horn ring.

[BlueSideUp]

Thank you for the help John & Harry....

1. The headlight switch was a fairly easy repair. As HarryD said the steering wheel and adapter need to come off. Once you remove the two screws holding the horn ring to the column there are four screws securing the plastic column shroud to the column. There are also two tiny screws on each side of the column. Be careful removing the column shroud as I'm sure there is a ridiculous Porsche tax for breaking it. Pull the top off first....

When repairing the headlight switch be sure to test it out before reassembly. My high beams would turn off when signaling with the stalk forward. A small adjustment is all that was needed to maintain the connection.

2. The voltage issue was pinpointed by John. The batteries were indeed in need of a charge so I removed them and charged the batteries individually. I also located a ground that was not attached in the engine compartment, I'm not really sure what it grounded but it probably shouldn't be flailing about the engine room. I have not had the opportunity to take the car for a spin yet so we'll see if it solved the tach issue.

3. The police car headlight high beam problem was pretty weird. I pulled both headlights and using my trusty multi-meter I checked for voltage. With the high beams on I had 12V (car off) at each white wire at the headlight harness and at the fuse box. With the low beams on I had 12V on the yellow wires. I tried switching the headlights side to side but still had the issue of the passenger headlight operating backwards from the driver's side. At this point I finally looked at the harness plugs and noticed they were different. The low beam and high beam were switched. I know the passenger's side fender was taken off of my car for rust repair about 5 years ago and it appears they did not correctly reassemble the headlight connector. Apparently the fix was to just aim the headlight lower.

4. My intermittently working passenger side parking lights turned out to be nothing more than corrosion on the fuse panel. I took the opportunity to clean up all of the fuse connections on the panel using a little sandpaper. I'm sure a more detailed effort is called for and it is on the list of things to be done.

All of these fixes also seem to have cured my slow wipers. They are normal speed now and even park themselves correctly! I just need to re-install the washer bottle to be back in business.

Thanks for the help guys!

[BlueSideUp]

I have put some miles on the car and I still have the bouncing tach. I also noticed that when I hit a bump in the road the oil temp/oil pressure gauge bounces.

In preparation for replacing my ground strap (which appears to be attached) I cleaned up the underside of the engine/transmission with Purple Power, brushes, and some water. When everything was clean I pulled on the strap a bit to see if it was split in two where it passes through the transmission mount and found it secured.

After cleaning I started the car to move it into the garage and had the red alternator light on. The light has never been on when the car was running so I checked with a multimeter and it shows battery voltage (12.5V). There is very little resistance between the engine and chassis indicating it is grounded.

Other than replacing the ground strap should I also be looking at other potential wear areas that the alternator wiring may be grounding out on? Perhaps a loose connection at the starter?

[BlueSideUp]

Now that the car has dried out a bit the alternator light is out and I get 13.8V at idle. Hmm, odd problem. I didn't do any cleaning in the topside engine compartment.

[bkreigsr]

all Koni's are adjustable.
on yours, remove from the strut, fully compress until you can feel the adjustment nut on the bottom of the shock engage, turn clockwise for hard, other way for soft. I run mine at 1/2 turn from full firm.

the trunk light has no external remote switch. there is a contact plunger in the assembly to turn the light on/off.

bouncing tach (if it were corrrect for your car) is also an indication that the dwell angle (if the dizzy were correct for your car) is something other than 38 deg. (usually gap too narrow)

[BlueSideUp]

Ah I'll check the dwell angle on with my handy dwell meter. I will also clean up the electrical connections on my gauges and the grounds. Replacing the transmission ground strap didn't change anything.

Thank you for the tip on the Konis, they sound just like the Konis I had on my other car.

Thank you also for the tip on the trunk light, I'll try putting some power to it and see if it works.

[BlueSideUp]

I did a little road testing today with the multi-meter hooked up to the clock wiring. I have a steady 13.6V with no accessories which is a bit low but not too bad. With the headlights on I get 13.4V, shouldn't a 55A alternator be able to supply ample voltage on an early car with just the headlights on? The voltage never varies but I will still pull the alternator for more testing and probably take it back for another rebuild.

I haven't had a chance to check my dwell angle but the car is drained of oil right now for a valve adjustment. Hopefully I'll finish that up in a few hours and be able to check the angle tommorow.