Another Alternator / Charging Question

[kcf7z]

I am trying to help my son with his project 944 which overall has been great. I have been a 911 guy for years without as much consternation from its electrical system.

I have searched and read this forum and others and I suspect that I know in general where my problem might be but I have not run across folks with this exact same symptom complex:

His car is an early 1985 (prefacelift). We have been working through gremlins and I felt we had undone some past problems. etc...

My current query is that when you start the car, the alternator light is on and does not go off until the car is driven for a bit. Maybe an eighth of a mile. During this time frame the interior dash lights or OFF. After driving this distance, the light goes out and the dash lights come on like magic.

If you then stop the car and let it idle, the light will not come back on and the battery terminals measure 13-14 volts so the alternator is working. If you check the battery just after starting, the voltage is 12 and the alternator is clearly not charging. SO... it is a problem that "repairs" itself after driving a short distance. It is not REV dependent it does not seem as sitting at idle and revving the engine does not fix it.


The battery is new, the alternator is new. It was doing this before I replaced the alternator as I thought this might fix the problem but it did not.

I know that there are many threads about these problems but this problem was a little different others. Is it possible that the Blue wire is the issue, but if so, why does the alternator start up with time?

[huskerick1]

While I haven't had this specific issue, I can say I spent countless hours troubleshooting various unrelated electrical issues - the underlying issue? Old, internally corroded battery cables. I would strongly suggest anyone with electrical gremlins start with new cables... Instantly, my low alternator charging, dim lights, and other issues were resolved once the old, corroded cables were replaced. Do note you cannot tell the condition by an external viewing as mine looked mint - but all corroded internally.
Food for thought...

[Dano944]

Before I drove my inherited 944 home, I had a Porsche Shop do a full service. They found the alternator to be bad and replaced it. The symptom I saw from my father-in-law was that he was constantly replacing fuses. I haven’t had any fuse issues. The repair shop stated that a faulty alternator would not produce enough electricity and cause fuses to pop. So my question: Why not simply replace the alternator? Start fresh.

[kcf7z]

Thanks for the responses. I did replace the alternator yesterday and symptoms seemed about the same. My son drove it all day today as a test and he remarked that he left the car off while playing some basketball with friends and it started right up with full interior lights and no battery light. It seems that the car being Warm has an effect so battery and alternator cables and grounds that may change when warm may be the trick. Now just trying to find a good way to replace all the main cables.


I have had my 1979 911 turbo for 20 years and the only electrical problem it has had are the headlight washers.

The 944 is trying to break my brain

[Dano944]

What about finding a good independent Porsche shop? They could analyze the electrical issues and maybe solve the problem.

[kcf7z]

I could but I have always been a glutton for punishment and trying to figure things out

I have restored my 911 mostly on my own.

The Porsche shop can be a stop but not a lot of options here in Nashville for these old cars.

Most shops in Nashville use this one electronics repair spot for old cars with electrical gremlins and I have heard they are great but the line to get in is a mile long and the wait when your car arrives is about the same

[wwdwgs]

OP,
PM sent to you.

[originalowner]

Originally Posted by kcf7z

During this time frame the interior dash lights or OFF. After driving this distance, the light goes out and the dash lights come on like magic.

This is a head scratcher, and I enjoy solving these puzzles. I'd like to clarify this comment. By this, you mean you are driving at night and the lights that illuminate the speedometer, tachometer, etc. do not come on, correct?

[kcf7z]

It is a puzzle and I am happy for the hive minds that like to help.
Crank car … fires right up and battery light stays on. The dash lights are off. Everything else works roughly. Voltage at battery at this point is 12 ish so No charging. Rev the car… no change. Drive the car about 200 meters and battery light is off and dash lights on. Stop car and leave at idle and voltage at battery 13-14 V so charging.. all good.


Drive car all around as much as you want and battery light is off and dash lights on albeit dim.

Stop car and return to it with it still warm… 30 min to 1 hour and restart. No battery light and good dash lights.

Main problem here is that we live 1 mile to my son’s school and this problem seems to be keeping the alternator from charging in between trips that are short … after one month of driving the battery discharged and with it drained I could not easily jump start it because the alternator does not engage until it’s driven a little bit.

I thought it was the alternator or voltage regulator so replaced both but really no big difference. Maybe a little better but no solved

[wwdwgs]

OP, did you bench test the old alternator?
Can you bench-test the alternator you have now?
Do you have a good spare battery to temporarily hook up to your 944 and test this way?

[wwdwgs]

OP, did you bench test the old alternator?
Can you bench-test the alternator you have now?
Do you have a good spare battery to temporarily hook up to your 944 and test this way?

[originalowner]

>No battery light and good dash lights.

Again, is this the illumination lights, or the problem indicator lights?

[kcf7z]

The illumination lights for the gauges not the warning lights —they all work fine and the battery light goes out when the illumination lights come on and the alternator is then charging based on voltage increase at battery terminal to above 13

I can take the old alternator to get tested as it is out just to see
The new one installed seems to perform maybe a tad bit differently/ better but general symptom persists

[originalowner]

Originally Posted by kcf7z

The illumination lights for the gauges not the warning lights —

Thanks. My analysis of the schematic is that there is no way the alternator and illumination lights are related (and I'm an EE.) No single failure, and that is what your description implies, can cause this, if the schematic is correct. So, the schematic may not be correct (I have a list of things not correct on the schematic, so this would be far from the first error in it.) Or, and I sadly admit this, I just don't see the connection, and in the end, I know I will be wrong about this. I can find ways for one to be a problem, or the other, but not both from the same, intermittent, problem.

So, my advise would be to fix one of the problems, and hope it fixes the other. I suggest going after the illumination lights. Because this can be done when it is cold and failing, and diagnostics can be done in your garage with the engine not running, giving time to diagnose things. I would start by wiggling fuse 12 in the fuse/relay panel to see if continuity there is the issue. Following that, I would get access to the back of the brightness resistor wheel part of the headlight switch and probe the voltages at both sides of the connector to see if there is an issue there.

[wwdwgs]

originalowner,
You may have noticed,, that German, especially Porsche's, wiring is very intricate and integrated. My friend onece had a misfire on 911 because of faulty light bulb(s). I, on the other had, had some problem and it was the front blinker, which was diagnosed and fixed by only one mechanic, who was an EE before he even started to talk. All other local mechs couldn't fix that problem.

you mentioned a fuse. Don't you think that i'ts would be a good (and painful) idea to check and clean all the fuses and relay board sockets?
Could it be a built-up resistance, that "breaks" when the components get hot (electrically) and "expand"?

OP, we still don't know, at the least I don't, if your car exhibit the same "lights" problem when warm and when you shut off and restart your car.
another question to OP, can you tell if your car's wiring was tempered with?

[kcf7z]

The problem does seem to resolve when car is warm. Once the alternator light goes out and the dash lights come on this resolves. You can then turn the car off and let it sit for a while, maybe an hour or so then restarting the car results in immediate turn off of the alternator light and the dash lights come on. The condition is liveable but we had a battery discharge that left us trying to jump start his car I think because he was driving a very short distance to school over and over again and the alternator was not starting. Because the alternator does not immediately come on in this condition then jump starting required letting the battery charge enough to drive it far enough to have the alternator start in this condition or else the car would die.

I think the dash lights not illuminating has to do with the voltage not increasing because alternator is not immediately coming on. I think this is just an effect:


And yes the wiring has been manipulated through the years and I have been going through multiple issues and solving them in at a time.

I am sorry I did not go into all of the others but they may be important
1. I have changed both the Hazard light switch and headlight switch but I am left with 2 problems here :

No low beams bilateral but everything else fine


2. No hazards
But fine blinkers solo

3. Windshield wiper blows fuse when turned on and I have been through it. I have it disconnected and ran a separated related circuit to bypass 944 fuse box after changing the stalk switch and checking all the wiring here with no fix.

The alternator issue may just be part of the bigger bugs introduced by previous owner.

I figure a good electrical
Shop may charge more than the worth of the car to diagnose and fix but may be necessary

[originalowner]

>I think the dash lights not illuminating has to do with the voltage not increasing because alternator is not immediately coming on. I think this is just an effect:

A likely cause of this would be a prior owner switching out the bulbs for LEDs, which are far more sensitive to voltage than a normal bulb. They also have a minimum operating voltage.

On to the blue wire. I'm now wondering if the same prior owner swapped the alternator bulb out for a LED as well. The LED does not draw as much current as a standard bulb, and this current is used to excite the field windings in the alternator on startup. Eventually your alternator gets going, and excites the field windings by itself. If LED, this bulb should be switched back to the original type.

[kcf7z]

That is a great thought
They look incandescent when they come on but I will check them
I also have not put in new bulbs through but have a slew of incandescent replacements

[Monkey Wrench]

every circuit is or should be a complete circuit when energised.
check battery grounds engine grounds and alternator to ground is where I suspect the issue lies. you replaced alternator already. look for any jury rigged mods LED schemes and if you don't change bulbs you can install a temporary test lamp in its place.
you can use a black jumper cable to substitute the ground path or check it for resistance. there should be no or very little resistance from any ground point or ground wire to negative, if there is you found a bad ground.

from the ground of the load there should be near zero voltage to the ground post.

if you measure before the load now you will have voltage, that's the voltage drop of the load,
prior to the load the hot wire, check that against the positive terminal, is there any difference, in other words iis there a load or a voltage drop that is in seroies wiht the load.? if so locate it..

the hot wire at the battery has 12 V, measure from there and any comparison to the hot post should be minimal, if the wires or fuse holders or fuses themselves or things like bad wire, weakly sprung or dirty spade connectors have resistance that will be a voltage drop, find the reason for a voltage drop on the positive side if there is one, if no measurable resistance then it's ok.

check from the hot lead to the starter and any other wires connected, look for any bad connection in the hot supply leads.

I don't think the lights are involved with the ignition switch on your 944 but on many circuits the hot is fed to the key , through the key switch which is not the key lock it is the switch. and the on position of the key could have resistance. the key switch could be dirty and have resistance. check if it does or not.

a difference between the hot wire at position 2 or run at the key shoul=d be close to the voltage of the hot battery post, if it is a lot different here is a voltage drop on the supply side.

the voltage at the negative battery post is 0 the pos is 12 V approximately, yes depends if its running.

try to look at each circuit as a complete circuit, it starts at 12 V and ends at the negative post, through the circuit there will be voltage drops, any bad connection will make resistance, make heat and cause a voltage drop.

you can check the voltage drop through fuses, they do present some resistance to the circuit and that is measurable. it is normal for a fuse to have a small voltage drop because the fuse is basically a resistor, its designed to blow if overloaded but in normal use there is a slight voltage drop across each fuse..

put your meter lead on negative post , with the postitive probe check both sides of each fuse , also check the spade connectors to that fuse, as you go around the circuit in question you can write down the voltage comparison between hot or ground and points of the circuit.


it will start at 12 V and go through different wiring locations and end up at the battery, finding the trouble is usually as easy as locating any point where there is a voltage drop where there should not be.

any switch can be dirty and present a load and a voltage drop or fail to close completely,, you can check that with a meter.

if you'd do not understand what is involved in a circuit or perhaps it is complicated by other circuitry, try to stay focused on one circuit at a time and assure yourself wheatear or not you have connection issues.. bad grounds dirty connectors. check the schematic, you can also follow wires about in the car visually..

if you find a suspect problem area check how tight he spades fit, if its a relay try using just one wire to check each spade connector in the socket to see if it has tension..

when a bad connection occurs you may see blackening, that "dirt" hampers and adds resistance, heat caused the metal prongs to get hot. if the copper and or brass is hot and then quenched, that removes the spring of the metal and it becomes weak and if that's a spade connector now it wont fit very tight or keep its tension because metallurgy was affected.

the euro fuses are horrible for getting corroded, the brass springs that hold them can get hot and loose tension.

what Id do is just unhook the battery snap a pic of th efuse locations and values. pull all the fuses, clean all the connectors and parts, dont pull more than one wire out at a time but do look at each connector. you cna use some alcohol or maybe a brass brush get everythign shiny and fuses replaced then hook up your battery again.

people tend to ignore the black ground wires, youll find them all over the place, remve every one you see clean it, you cna put some dielectric grease to prevent or slow further corrosion if you have a problem wiht your headlights check the grounds, if you have aproblem wiht anything else electrical check its ground path, the ground path back to negative is just as important as the hot fed is but for soe reson peopletend ot focus on the positive and forget the negative is just as important, bad grounds cause a voltage drop , they rob power from the load often it is easier to just go over the whole car and spend a half a day cleaning every ground point than it is to worry about troubleshooting..

I have an 85 too and I know wiht volvo, near those years there were certain years around this time where the copper they used wasn't very pure, the wire discolors faster when you do a splice and you are opening up wires you'll get a sense of that ..

copper wire isn't really just just copper , wire makers will throw other stuff in because copper is pricey. now its actually an alloy. some wire has less copper in the alloy and won't last so long against the elements as softer and more pure copper..

brass is an alloy not an element it is a mixture of copper and nickel with other ingredients it also can vary , some connectors are steel with a coating of another metal. brass may be desirable to make it more springy than soft copper so the alloys are chosen by manufacturers to save cost and also to perform their function.



if you go run out and buy cheapest you can find brand of made in china battery cables do you think they will be good materials? They have likely saved on the metals back at the factory, so then what you are actually getting may be inferior copper to OEM.

to clean the post clamps try mixing a jar of baking soda and water, stick the end of the cable and terminal in there for a day then clean it, the baking soda helps.

then you can use your favorite way,, sandpaper a file, a battery post cleaning tool or steel wool ,.. careful steel wool can short stuff and if it shorts it can burn, if you don't believe steel burns try lighting a bit of steel wool with a match yes steel burns quite well when it is in fibers.

on a 35 yer old car is it worth just replacing the cables? I think so but maybe don't put the cheapest ones you can find, oversize is ok , undersize is not ok.

my giues is ou have a bad alternator ground to the block or a bad engine ground but thats just a guess, and my second guess is a bad ground..

any light you have issues with check the socket and the wires to the lamp assy and the ground point, don't just look the ground, remove it and clean it,,

new bulbs are a dime a dozen on rock auto they are becoming obsolete so just stock up on bulbs and change any you even suspect are bad, ,if you are cheap sure you can clean the sockets, OEM bulbs nay be better quality and same for OEM fuses.


to check any circuit try going from hot all the way through the circuit , it won't matter if you reference ground or the hot side, Just understand how to check the voltage drops through out any circuit. yo may need a extra long wire to extend your meter leads to the battery reference point. you'll figure that out.


make motes write them down and step back and look at where your voltage drops are. usually when things are working properly the only voltage drop is the intended load not the wiring that is feeding the load or back to the battery ground.
when part of the circuit is a voltage drop , ( bad connections) it steals voltage from the load and things may appear to be working in a sort of a brown out state.

example :
usually across a load in a working circuit you have near to 12V. if you have a bad ground you may see 6 volts across the bulb and 6 volts between the ground wire and battrey ground fixing the bad ground problem ( dirty connection) results in zero volts between the ground wire and battery negative and also restores 12 V across the bulb.

two bulbs in series share the 12 V each sees 6 volts of drop.
two bulbs in parallel each see 12 V

most things in a car aren't wired in series,,

you may have 3 dash lights , they will all be wired in parallel. each has a direct connection to the battery hot and to battery negative each sees a 12 V drop across the bulb. the hot and the grounding may be shared between all 3 somethign is goofy with your dash lights.

the red charging indicator light , if it is charging then it may be not a huge issue. I have a car here, it lights when i start driving.. if I turn the headlights on it goes out,, why ? not sure,, since its charges the battery ok I haven't dug into why. it seems normal otherwise,, like the oil pressure light, it lights when I turn key on.. often it just prompts me to turn my headlights on.. the cause I don;t know , its a 66 volvo with a GM alternator. the alternators are pretty generic it contains the regulator, that is where the red light comes from.. but it charges anyway.. whatever that issue is I think I have it too.

in your case you replaced th ealternator it did not fix it , try checking the ground wire of the alternator to the block and then to the battery.

[Monkey Wrench]

I had a car that failed to charge it wasn't obvious at all but the alternator ground to block it looked fine but it was dirty, it caused it to not charge. you likely have a blue wire connected to the block near the alternator,, check that one. I suspect yours may be dirty where it connects to the block.. if you changed the alternator you could have unhooked it, then transposed the wire to your new alternator, but failed to unhook where it is connected to the engine or ground point.. it is necessary for charging. also check that th eblock is actually connected to the body look for a ground strap that grounds body to engine.

hey if you add an extra ground to the alternator, to the body or to the engine or to the battery it wont hurt anything,, a jumper cable laid in parallel is an easy quick check just to confirm alternator or block grounds are ok.. better to clean it but if you can strap a ground across just using a jumper cable as a temporary fix as a test, and see a difference,, then you are onto something.

if you heat copper or brass and quench it it becomes soft, if you heat it and cool it slowly that makes it more springy, you don't need a lot of heat and you can change the metallurgy so you can re harden it to restore spring tension but it may be close to plastics. probably best to do a neat splice and put a new terminal on it.

often things lik efuse terminals, the springy holder things, they can get hot, loose tension and then its both loose and dirty. I know women like that. lol but your fuses you don't want loose OR dirty ;-) as you install the fuses after cleaning press on them and compare, do you have weakened springs? are they not pressing well against the tips of the fuses? are all the fuse tips clean? are they falling away from the porcelain part? they are easy to break.
if you need ot repair a wire,

to do a neat splice,, clip and strip the wires, make sure they are clean. do a western union splice
look here:
https://en.wikipedia.org/wiki/Western_Union_splice

put heat shrink not black tape on the wire then splice then solder, then pull the heat shrink overtop and use a lighter to shrink it, don't use black tape unless you absolutely need to. often what I will do is do a real nice solder joint then realize I forgot to slip on my heat shrink,,, so I can cut it apart, start over and repeat it then.. I must love soldering. Put the heat shrink on FIRST!

any connection I find that is properly heat shrinked is trustworthy and ok, i know I did that.. but any blacked taped connection is not mine and is suspect, so I find those I unwrap to see. often some dimwit twisted the wires wrapped it with tape and said good enough .. that crappy workmanship will often come back to haunt you so just bever do that unless it is a temporary test or similar. always solder !



never put heat shrink over any splice that is not soldered.. you'll hide the cause of a problem.

that splice will have no resistance and no measurable voltage drop.. if you spot wire that when you strip and it it it is green or dirty looking change as much of that wire as possible without it becoming a huge project. if some previous owner made connections wrapped in black tape undo them, if they seemed to not solder or make a lousy joint then look for other places they did the same.

if you always make good splices you'll never have any issue with bad ones that you did.

some dot know how to solder, keep the tip clean, load it with solder, take a wet sponge and wipe the tip and make sure the tip always is wet with solder, if the tip wont take solder , stop, clean the tip re coat it with solder.

often people will hold their solder iron on too long, it should heat and be done quickly if the tip is dirty you'll have to struggle and you'll heat to long.

if you want to contain the heat to the point you are working on try clamping small vice grips or an alligator clip on the wire to suck heat away like a heatsink.
just so you aren't melting the insulation an inch from where you are soldering.

the battery cables buy new ones , don.t mess around , idf they re old they are done they aren't expensive or proprietary.
you don't need porsche brand battery cables any more than you need porsche air in your Porshe tires. Don't get sucked into that proprietary nonsense. its a hunk of wire with a standardized battery post. often better quality wire also has more fine strands, maybe ask where you buy your batteries. If you can find ones not made in china you are lucky.

I wouldn't take this to a Porsche specific dealer or mechanic What you need is a guy that can troubleshoot electrical problems.. or patience and DIY time..
Sure a porsche shop may have one of those, so do lots of smaller shops.
if the guy can't check things like voltage voltage drops, continuity and resistance, he isn't worth hiring. there are licenced mechanics out there that never learned how to troubleshoot electrical circuits properly.. try not to become overwhelmed.. it's just a few circuits and each isn't very complicated on its own.. the electronics , the ECU that is a bit different.

it sounds like you may have more than one unrelated electrical issue..