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Need Help 987 Cayman S

4K views 45 replies 8 participants last post by  deilenberger 
#1 ·
I’ve been hesitant about posting because I made such a stupid mistake and wasn’t really ready for the roasting but here we are. I managed to hook my new battery up in reverse, positive to negative and negative to positive. Initially all electrical pretty much worked but wouldn’t start. I could hear the starter engaging but not spinning. I changed the starter and same. Pulled on the wire coming from positive battery terminal going to the firewall and the car started with no codes and ran for 3 days without issue. Last time it cranked it ran for about 5 seconds and died. The fans stay on, locks and trunks open, no dash but it does recognize the key, windows and radio don’t work. When I connect the battery it arcs. Any insight would
 
#5 ·
As was mentioned - you certainly weren't the first to do this. It seems not to be uncommon (not exactly common, but damn close to it..) It seems there is always some damage.
Also, since tugging on the firewall wire made a difference once I thought maybe it was a weak link. I pulled the box, checked all the fuses and threaded the post instead of the push on connection.
Can you take a photo of where/what wire you tugged on? And I don't quite understand "threaded the post instead.." - what "post"?
The arc is pretty big, the connection will stick to the terminal. I’m guessing it has to do with the fans constantly running. I’m not a PCA member. Thank you for your response
Sounds like a failed component somewhere.

Sometimes after this sort of incident, it can take a while before components start failing. That's what it sounds like. You're either going to have to make an investment in a diagnostics tool, or take it to someone with a diagnostics tool. If you feel competent to effect a repair once the cause is identified, I'd suggest buying a tool with Porsche specific software. Durametric, Foxwell (NT530) and others make such tools. These will allow you to try to communicate with various control modules in the car, and try activating them using the software. The modules, if you can't connect - that's a big clue. If you can connect and there are some stored codes in the modules - those are a big help in diagnostics. If you can connect to modules and use the software to monitor and activate some of the module functions, that can be helpful in tracking down the problem and what needs repair.

Right now - we know something is broken - but I wouldn't hazard a guess without more diagnostics info. The next step is yours..
 
#6 ·
The post in the center of this has a slide on connection with a plastic clip that holds it in place this is the wire I tugged on and initially got a response. I said through the “firewall” but it’s actually right near the battery where the positive cable exits the frunk. Mine had rust on it so when I removed it to inspect fuses and connections I threaded the center post to and bolted the cables to it to ensure a good connection
Automotive wheel system Font Auto part Rectangle Engineering
 
#10 ·
I believe this is the 80A fuse. If the car has any electrics working - this fuse is OK..
(Top item in diagram)
I will also say that when the battery was hooked up reversed the fans came on as well. That relay could be hung up or just pure coincidence. I have access to diagnostic tools so I’ll wait and see.
The bottom item in the diagram. the fan controller is basically attached directly to the battery via the 80A fuse, so a reversed battery connection stands an excellent chance of damaging that controller.
Slope Rectangle Line Font Parallel


There are very few "relays" actually used in any modern vehicle. What used to be relays are now electronic switches, controlled by a computer circuit responding to inputs from various sources (like temperature sensors.) A relay might survive a reverse voltage situation - some of the solid-state switches won't. This sounds like the case in this situation.

Once you're connected to a Porsche diagnostics tool you should be able to access the blower control unit and determine if it failed. As to what's preventing it from starting? You should be able to determine that when connected to a diagnostics tool.
 
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#11 ·
I would think a decent scan tool would be quite helpful. I have the Durametric which is OK, but since it doesn't work on my Macan or at least do anything useful I wouldn't recommend it. I have an iCarsoft CR Max and it is useful for our Porsches and VW. Back to your situation, I'd be suspicious of your alternator. I believe there are regulator diodes that could possibly be toast due to the reverse current. Also if you have a voltmeter you might want to check the battery voltage. Good luck we all make mistakes on the road to success.
 
#12 ·
The battery checks out at about 12.5v. I would think, but could absolutely be wrong, if the alternator was bad it would still run but not charge. Could it possibly be fried and sending current in the wrong direction? I have access to several scan tools, my stepdad owns a diesel repair shop and I’ve used them before to clear codes I’m just waiting for him to get a little free time.
 
#16 · (Edited)
I rather doubt if your stepdad's tools would be a lot of help. It's unlikely these tools have the Porsche specific functions that dedicated tools (or tools with installable software) have. Go big and spring for a Foxwell NT530 ($160 or so with the Porsche software) - you'll find yourself relying on it in the future when you really want to know what's going on. It will be cheaper than replacing parts (like the starter) based on guesses or Internet suggestions.

The alternator can't put out reverse polarity voltage/current. It has rectifying diodes in it that convert the AC into DC. Those won't change in a manner allowing reversed polarity. They could open - causing lower current capabilities, or short - putting a large amount of "ripple" on the output from the alternator... (BTW - some history - I'm that old - a "generator" which used a fixed magnetic field could be caused to put out reverse polarity voltage by hooking up the battery backwards. Did that on my first car, a 1957 DKW 3=6.)
Crowbar would be such an inexpensive preventative measure. They don’t want people to service their own cars anymore. What I did was dumb and immediately hurt my pride. I’ve changed shifter cables, shifter, two window regulators, coolant system seal, full exhaust, radio head unit which took a lot of figuring out especially with the Bose system and lots of miscellaneous other things. Only to get my *** kicked by a battery.
"Crowbar" is a heavy-duty electrical device unsuited for a car. It's designed to limit current surges.

What can be used and is used on many automotive devices is simple diodes, two of them rated for the amperage the device consumes will do the job. They pass electricity in one direction and don't pass it in the other. Correctly installed reverse hookup of a device simply means it will never see the incorrect polarity. There won't be any damage.
If the fans constantly run I wonder if that might be throwing the car into a mode to save itself preventing any starting. Just random thoughts until I get the scan tool here.
Nah. That level of intelligence isn't built in. The fans can (and sometimes do) run with the ignition off, or when turning the ignition on - if the coolant temperature warrants they be on.

Get the code reader. Scan all the modules in the car. Report back and we can try to lay out a logical troubleshooting path that avoids the "fix by replacing parts" diagnostics (which can be a VERY expensive way to troubleshoot things.)
 
#13 ·
Yeah I agree, but immediately thought of the diodes. Kind of interesting that there isn't a crowbar of sort of circuit to shunt reverse polarity current to ground. I've repaired all nature of medical equipment when I was part of the proletariat and most devices had that protection. It will be interesting to see what codes are reported. I guess worst case scenario is the ECU, but it is odd that the car ran for a few days.
 
#14 ·
Crowbar would be such an inexpensive preventative measure. They don’t want people to service their own cars anymore. What I did was dumb and immediately hurt my pride. I’ve changed shifter cables, shifter, two window regulators, coolant system seal, full exhaust, radio head unit which took a lot of figuring out especially with the Bose system and lots of miscellaneous other things. Only to get my *** kicked by a battery.
 
#17 ·
The scan tools that he has are a few grand each and he said he would download the programs needed for my car. I’ve heard my fans run after driving and parked for a few minutes but from battery hook up cold and never shut off isn’t normal. I’ll definitely report back when I find something out.
 
#18 ·
I'll be interested in hearing about success with the tools he has - and what tools he's using. I do know from experience - the Snap-On tools are not particularly good for Porsche's even with their horribly expensive Porsche module. Price doesn't necessarily equal capability.

And my point on the fans was that the car wouldn't be programmed to protect anything (by not allowing engine starting) if the fans come on immediately with the key since this can be normal behavior of a correctly operating fan/controller.
 
#19 ·
I’ll definitely update. I know the one I’ve been using isn’t Snap on. I’m not sure it will work, only can hope. I’m not afraid to admit when I’m wrong. Honestly knowing I can buy my own that will work for less than $200 has me thinking, especially since I own the car. The fans don’t come on with the key it’s immediately when the battery is connected. The only thing that changes with key is the ignition unlocks.
 
#21 ·
Something could now be reverse-polarized. If anything like a dynamo with windings was connected backwards, it could now be opposite due to being connected backwards. A fuse isn't going to know the difference in "polarity" in this case, so one isn't going to blow if you connected things backwards. You're looking for something like a diode or something that only allows electricity to run one direction. Any DC-motor would have run in reverse when connected this way. You say it was connected and drove normally for 3 days connected backwards with nothing apparently inoperative?

I'm surprised the computer couldn't tell the difference between +12v and -12v and allowed anything to operate in the first place. connecting jumper cables backwards could cause very bad things to happen, but you seem to be saying you just connected a single 12v battery backwards. RIght?
 
#22 ·
What I would do: I own a multimeter and an inductive clamp on current probe. Also have a variable voltage current limited power supply. I might be tempted to slowly turn up the voltage and watch where the current is going. Just to get a rough idea. or remove a fuse, use clip leads to get access to the current, flowing through the fuse and measure the current that way. The hardest thing for me, would be to try to avoid guessing, and acting on a guess. I always guess wrong and waste time. Instead, figure out someway to find the smoking gun. I’m sure this is already stuff you’ve thought of.
 
#24 ·
Ok, so you're saying you temporarily (for a minute) connected the battery in backwards. You realized your mistake and swapped them around. It drove fine for 3 days and now the battery is dead? Is that right?

An alternator has diodes in it as it produces alternating current which must them be converted to DC voltage for use in the car. It could be that these diodes have failed or that the alternator itself is now reverse-polarized (I don't know how the windings between a generator an alternator differ), so you basically have no charging system. A new battery would work, but would also go flat in a few days. You can check that with a meter, of course, verifying the output voltage from the alternator. Back in the day, people would actually take apart alternators/generators to swap out the diodes, brushes, and the bearings to re-new their alternators.
 
#25 · (Edited)
Ok, so you're saying you temporarily (for a minute) connected the battery in backwards. You realized your mistake and swapped them around. It drove fine for 3 days and now the battery is dead? Is that right?

An alternator has diodes in it as it produces alternating current which must then be converted to DC voltage for use in the car. It could be that these diodes have failed or that the alternator itself is now reverse-polarized (I don't know how the windings between a generator and alternator differ), so you basically have no charging system. A new battery would work, but would also go flat in a few days. You can check that with a meter, of course, verifying the output voltage from the alternator. Back in the day, people would actually take apart alternators/generators to swap out the diodes, brushes, and the bearings to re-new their alternators.
I'm one of those people who used to take alternators and generators and voltage regulators apart to fix them.

I can assure you - due to the basic differences in how an alternator and a generator work (one has permanent field magnets, one doesn't, one has a segmented commutator the other doesn't) that an alternator will never put out reverse polarity.

It may however put out a voltage that measures OK with a voltmeter, but has no current behind it (limiting charging) or DC voltage with a high percentage of AC ripple on it (caused by shorted diodes - the clue for that is the diodes often "sing" - make a singing sort of noise 'zzzzzzzzzz' when shorted.) And sometimes both happen at the same time.

The battery in the car works like a great big capacitor and helps to dampen the AC ripple. It's enough with a healthy battery/alternator that the ripple isn't an issue. If the diodes are shorted, or the battery is weak - enough ripple can get through to disable some devices and perhaps destroy other devices.

Part of what causes electronic device failures after a battery reverse connection is the sparking that occurs as you connect the battery and then in a panic disconnect it. That sparking causes high-voltage spikes to travel through the entire electrical system of the car, causing damage that may not immediately show up (eventual solid-state-device failures - used by "T" failures of the device substrate.) They might show up hours, days or even weeks later.

That's also the reason that in general - jump-starting of any modern car isn't recommended or suggested by the vehicle manufacturers. They typically call for charging the battery, sometimes with the positive lead from the electrical system disconnected. It's not JUST the reverse connection that causes the issue (as I mentioned - that's pretty simple to protect against) - but it's the high-voltage spikes. That's harder to protect against (think surge-protectors, typically once they see a surge the protection is now no longer active - the device sacrifices itself to protect the other devices that are connected to it.)

I believe what he said was - he reversed the battery connection, disconnected it, reconnected it correctly and the car ran. Now after 3 days it no longer runs despite installing a new battery. I think he also made mention of the fans running as soon as he hooks up a battery to the car.

The hardest thing for me, would be to try to avoid guessing, and acting on a guess. I always guess wrong and waste time. Instead, figure out someway to find the smoking gun. I’m sure this is already stuff you’ve thought of.
David made a very astutue comment here.. guessing gets expensive since the last part you change will be the defective one - but you might change a LOT of other parts getting there. Hence my suggestion (strong suggestion) of getting it hooked up to a diagnostics tool.
Or take it to a dealer who I'm certain is no stranger to this issue.
 
#27 ·
Update. I haven’t got the scan tool yet but I did find the relay in the rear trunk for the engine compartment fan, pulled it and same noise. I pulled everything back apart and dc the starter. Turns out it was the starter constantly spinning while battery connected. Once I dc’d it everything else in the car works again. I’m going to have the new starter tested tomorrow but is there a starter relay/ switch to lock for as well and location would be appreciated.
 
#28 ·
I think if you're intent on solving this yourself - it's time to man up for an AllDataDIY subscription. I can snip things from my subscription, but since your car (from memory) is a 987.1 and mine is a 987.2 - things may not be the same. Circuits might not be the same. Somewhere I posted a message about how to get a discount subscription to ADD that makes it reasonable for the average DIY'er to subscribe to.

Here is what my subscription shows for a 987.2 starter circuit:

Rectangle Slope Font Parallel Diagram


Before replacing anything - I'd suggest disconnecting terminal 50 on the starter. This is the power feed to the solenoid on the starter. That solenoid does two things - it connects high current battery voltage to the starter windings so the starter turns and it pull the starter pinion out to engage with the teeth on the flywheel so the turning starter will turn the engine over.

Since the starter motor is running, it's almost certain the starter solenoid is passing current to the starter motor windings. The question might be - if that's true - why isn't the pinion being moved out to engage the flywheel? This might point to a defective starter.

If you disconnect terminal 50 (yellow wire) - that should de-energise the starter solenoid. If the starter keeps running at that point - then there is a defect in the starter. If it stops when T-50 is disconnected, then you need to look upstream for the issue, perhaps at the stater relay they show in the diagram.

Good luck, let us know what you find out.
 
#30 ·
I did it as an image of the PDF - which makes it possible for people to view it without having to download it to their computer (some people just won't do that..)

Rectangle Slope Schematic Font Parallel


The diagram is basically identical for the starter part except for the PAS and MFI-DI (whatever those are..) but the important part is terminal 50 on the starter. This will be the SMALL wire going to the starter, in the case of a 987.1 it appears to be red/gray instead of yellow as on the .2 car. Disconnect it - hook up the battery - if the starter turns the solenoid on the starter is cooked and you need a new starter.
 
#31 ·
last night I disconnected the small single wire before anything else and it still spun when the battery was connected. I had the starter tested today at autozone and a starter/ alternator shop and both said it was good but I suspected it would test good and still be the problem.
 
#32 ·
Do this at your OWN RISK.. I'm not telling you to do something, I'm telling you what I would do in this situation.

Assuming you have the starter out.. and you have a 12V battery and some jumper cables..

Find a way to secure the starter to a bench of some sort (a large vice would work, or even wood clamps)
Carefully connect the black jumper cable to the negative terminal on a battery and to the housing of the starter (normally there are lugs with holes that are used to bolt the starter to the block.. attaching the negative cable to it should work fine.)

Then take the positive terminal and connect it to the big terminal on the starter (terminal #30) and then to the positive side of the battery.

Does the starter immediately start turning? If so - the solenoid is bad.

If not (it doesn't turn) - proceed to the next step:

Starter connected as above - take a small wire and run it from terminal 30 on the starter to Terminal 50 (the big terminal) do you hear a "clack" noise and does the pinion on the starter output move out from the starter body? And does the starter start turning? If that happens the starter is probably OK.

DO take off any rings/watches/metal jewelry before starting this test (DAMHIK - IJD) DO be very careful not to cross the cables from the battery or let the ends of the jumper cables touch each other.

let us know the result of the test above.
 
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