by "K-Roll-PorscheTamer" (k-roll390)
Published 06/19/2017 at 20:59
by "K-Roll-PorscheTamer" (k-roll390)
Published 06/19/2017 at 20:59
Tags: 931Lyfe
STARS: 1
I’ve found a big one in the electrical system after returning from California, I think. Disconnected the battery that’s only a couple months old, put it on trickle charge and let it sit for 18 hours, measured 12v, and connected it back to the car only to get a 6v reading minutes later after trying to turn on the lights after replacing the rear tail light bulbs but that may be because the cause of the drain is too much to light up the bulbs. I thought I’d just finish installing the proper fittings to the fuel pump and then it would start but now it’s something I’ve never dealt with.
So I’ve got an intense parasitic battery drain coming from who knows where in this car that’s come from nowhere that’s preventing me from cranking the engine or even turning it to “ON”. I have no idea what I’ve gotten myself into with this car, or how to read wiring diagrams, but this is proving mentally challenging and stressing because I’m a bit lost on what to do.
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 21:09, STARS: 1
You need an ohm meter setting on a multimeter. It’ll read between zero and one. It measures resistance. It won’t point out where the short is but the less resistance the closer you are.
Since you have the tail open you likely have a positive wire touching the negative frame of the car somewhere near there. Maybe a spade terminal came off. Your fuse should blow and stop that but since it hasn’t the short is likely between the battery and the fuse box.
Sorry if you knew all this. Just trying to be helpful. I’m sure others have a better method than mine. Good luck and godspeed.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 21:14, STARS: 0
My multimeter has resistance settings, but I’ve never used it becuse I don’t know how. I really haven’t much of a better idea than you do in regards to this. :(
How would I know if there was a short or blown fuse? Is this something that can be seen? Especially since I replaced quite a few of them last month.
"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike)
06/19/2017 at 21:22, STARS: 1
Fuses can easily be seen, but you would have to check each one individually. You can easily tell if a fuse is blown by looking at the fuse - they are usually transparent plastic so you can look into them to tell. If you look into the fuse and see that the ‘bridge’ contact within it is singed and doesn’t reach from one side to the other anymore, then it’s blown.
Not sure about your Porsche, but my Accent has a little plastic fuse-puller tool that is stored in the engine bay fuse compartment. If your 931 has one, you can start pulling fuses to check if they are blown. If you find one (or several) that is/are blown, replace it/them with a similar one/ones. If the same fuses blow again, then you know the issue isn’t coming from the fuses themselves...
...that was all probably very obvious, but you asked how you’d know if there was a blown fuse, so I hope that helps!
Blown on right:
These pics are of the mini blade fuses....the larger ones are the same principle to check though.
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 21:26, STARS: 1
Set your meter to the ohm setting. Look at the reading. Touch the probes together. It’ll be self explaining.
A short, which is what you have, is when some part of the positive meets the negative someplace not useful. The entire car frame and body is connected to negative. This allows car makers to only wire for positive. So your tail lights have positive wires connected to a switch under your brake pedal which activates them and the frame of the car is connected to the negative. Saves 50% of the wiring.
If you take a battery and try to jump it but get the wiring backwards there’s a lot of sparks and a chance of fire. That’s a short. A fuse keeps a short from turning into a fire. It heats up and sacrifices itself. A thin wire will heat up like a toaster. A thick wire will heat up but likely kill your battery as fast as it can which is what sounds like you’ve got.
Why did you disconnect the battery to begin with? Was it dead when you got home?
It could very well be a bad battery. That much voltage loss that quick without a fire is actually a clue. Did you leave the lights on? If you drain a battery fully it might not take a charge again, especially if it’s a bit faulty to begin with.
I’d get a fire extinguisher handy and try a battery from another car.
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 21:28, STARS: 0
Those wrenches on top of your battery would conduct a shit ton of current without catching fire and do so before the fuse box btw.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 21:34, STARS: 0
These are the fuses my car and presumably most European cars of the era use.
"Urambo Tauro" (urambotauro)
06/19/2017 at 21:36, STARS: 2
To hunt down parasitic drains, I like to hook up an amp meter and start pulling fuses one at a time until the drain goes away to help narrow down the problem circuit.
But your drain sounds more substantial than just a short in, say, the lighter or radio circuit... I think I’d start by investigating high-amperage circuits (the ones with thick cables) like for the alternator and starter first.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 21:39, STARS: 1
I’d disconnected it because it was dead because I’d forgotten to put it on a charger before I left and forgot to ask someone to do so while I was gone. But it was drained beforehand to the point it would only allow the car to click when I’d try to crank it. I only got it to click yesterday when I tried jumping the car for 10 minutes. But I have been even more incompetent and have left the keys in the ignition overnight, which has left the battery dead at least twice.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 21:40, STARS: 0
I don’t understand..Mind you, I removed the wrenches prior to testing.
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 21:42, STARS: 1
Yessir. They’re old school. They won’t cut your voltage in half of they blow though. Fuses are like lightbulbs. All or nothing.
Count your wrenches and make sure you have them all. They won’t blow. Nor will screwdrivers. You might also want to verify that the battery holds a charge when it’s not connected and then connect it and see if it still holds a charge and feel if the terminals get warm. If it’s still holding a charge but you don’t see the voltage while testing with the positive probe on the battery and negative on the frame it could be a shitty battery connection.
That’s the thing with electricity. Sneaky and invisible.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 21:43, STARS: 0
This just got more difficult, two unmoving cars in a garage and no place to jack one up in there. Only way I can reach any of those thick cables or wires is from underneath and I’m not sure what to do when I see whatever I see. This isn’t the best thing for me to do all by myself I think.
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 21:44, STARS: 0
I meant if you lost one where it was completing a circuit.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 21:45, STARS: 0
Oh.
"Urambo Tauro" (urambotauro)
06/19/2017 at 21:49, STARS: 0
You might not have to access the full length of the cables. If you can just reach the other end of each cable (like at the solenoid or alternator stud), you can check the connections, disconnect them if you have to, poke it with the meter, etc...
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 21:51, STARS: 0
Oh then you likely fried your battery. You’re using what is recommended for your car, which is out of date lead acid batteries. You can use newer but nobody goes backwards figuring that out. So while a gel acm battery might be okay with a bit of mistreatment, that one maybe not so much. The old ones physically break down and will charge but not hold it.
12 volts is 12 volts though. Try a donor battery. You’ll find our quick if it’s the batt or the car.
Sincere sympathy.
"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike)
06/19/2017 at 21:51, STARS: 0
Same story - with the Euro fuses, unlike the plastic ones, the path the electricity is taking is that copper contact along the outside edge of the fuse (where the plastic ones have the circuit path embedded in the plastic). Check the narrow part of that copper contact and if that is singed/broken, that fuse is bad.
"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike)
06/19/2017 at 21:55, STARS: 2
If you inspect the cables and find a wire isn’t frayed but the material surrounding it is rubbed/torn off, it could be shorting out on something metal-metal. Wrap the damaged area up in electrical tape and then check the car. If all is well, you found your short.
"MM54" (mm54mk2)
06/19/2017 at 22:02, STARS: 1
Charge it up, re-connect the negative cable to the post. Use your multimeter set for amps (or a dedicated ammeter if you’re fancy) to make the connection between the positive post and the clamp. Rig something up so the positive clamp can’t touch anything, since it’s now hot and still pretty much flopping around.
Check on your meter what the draw is. It’ll be some amount, in your case it could be several amps if you dropped the voltage that far so quickly (or it’s a bum battery). Now for the actual diagnosis:
Pull one fuse at a time from the box, and check the amp readout (can do it yourself or with someone, the former just takes a little longer) and put it back. Eventually you’ll pull one that makes it drop a lot (a few mA could be the clock, dome light, whatever) - that’s your circuit to start looking for the problem on.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 22:22, STARS: 1
I’ll try my best.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 22:22, STARS: 1
I’ll check to see if any of the fuses are burnt tomorrow.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 22:24, STARS: 0
Does that mean I should get a newer newer battery then? It is a lead acid indeed, is a gel acm (idk what that is) better or more efficient or something of the sort?
I’ve gone through at least 5 batteries in the last year or two because of gremlins and personal incompetence among three cars now. :/
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 22:26, STARS: 0
This is a great start, it’ll have to be the former because I haven’t got anyone to help me.
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 22:51, STARS: 1
So the difference between old and new batteries is huge but if you’re killing them on the regular, old style batteries are at least way cheaper. They (old batteries) don’t tolerate abuse very well. If you overcharge them they boil the acid off and need the cells to be replenished with distilled water. If they die - all the way - the lead inside corrodes (basically) and while they hold voltage they don’t hold amps. Think of a bunch of AAA batteries that end up end making 12 volts versus the same number of 1.5 volt D cells. Same voltage, sure, but the D batteries have more to draw from than the quickly depleted AAA batteries. Imagine a big mag light but put AAA batteries inside of it instead of big D batteries. They’ll fit and it’ll turn on just as bright and be dead in 10 minutes.
Letting your battery die all the way causes big cells to degrade, turning your big battery into a tiny little one. Just an equally heavy one that takes up the same amount of space unfortunately.
There are ways of testing batteries and I think at least one one of the auto parts chains will test for free: O’Reilley. I don’t know how they run the test but I’ve overheard results while paying for something and they sound pretty definitive.
"K-Roll-PorscheTamer" (k-roll390)
06/19/2017 at 23:20, STARS: 0
Would you recommend trying a newer style battery if it turns out the current one is my culprit?
"Flynorcal: pilot, offshore sailor, car racer and panty thief" (flynorcal)
06/19/2017 at 23:49, STARS: 0
Not really. There’s no point in fixing engineering that’s worked for 30 years and doing so at 3x the expense for what is ultimately a side project.
If it were a race car and you could save 25lbs, different story.
"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike)
06/20/2017 at 20:19, STARS: 0
Any updates? :O
"K-Roll-PorscheTamer" (k-roll390)
06/20/2017 at 23:15, STARS: 0
Battery is good, most of the exterior lights are working (turn signals f/r, headlights but the motor is unresponsive, brake lights are unresponsive, one rear driving light works), and the car is now cranking ever so slowly. I found the last fuel leak and have to order another part for it. I will also order a new starter motor because the old one just has to go and I don’t think it’s strong enough to start the car, if that’s possible. Also none of the fuses look burnt from a visual POV.
After these plans fail, I’ll work on the surface rust until I can schedule time at a shop and they’ll have to finish what I’ve continued.
"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike)
06/21/2017 at 13:54, STARS: 0
Could be the starter motor, but it could also be that there is a short and not enough juice is getting to the starter to crank it over properly?
Brakelights could just be the brakelight switch - rear driving light not working could just be a blown bulb. Should be able to test the driving light by just seeing if the bulb is blown or not. Asfor the brakelight switch you should be able to check that with a multimeter.
Not sure how to suggest going about why the motor won’t fire...I would replace the starter. You could see if the engine is getting spark though? Even if it is cranking slowly, you can pull a plug and look to see if you can see a spark arcing on it when it does crank. If there is spark, at least you know some juice is getting through...?
"K-Roll-PorscheTamer" (k-roll390)
06/21/2017 at 18:16, STARS: 0
I replaced all the taillight bulbs properly as it’s the same on the 944. I’m not familiar with brake light switches so I’ll read up on that before I go into that further.
I still have this crown of grounds to clean (#2) that I just discovered is the ground for the relay/fusebox panel so I’ll clean those up and try again as well.
Having replaced the spark plugs and checked the ignition timing, there’s no reason it shouldn’t spark, and the wires and distributor cap and rotor were replaced by the previous owner correctly not even a month before me. I did see sparks the last time I checked for it which was a couple weeks before my trip. Both my dad and I confirmed it.
The car is scheduled to be towed to the shop July 5th, so lets see what I can do before then.
"RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars" (rallydarkstrike)
06/21/2017 at 18:35, STARS: 0
Good luck! :)