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YOUR RESEARCH996 low charging voltage.
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Disconnect battery
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Leading evidence: 'Disconnect battery' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Disconnect battery' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion · Original poster
Or replacing the small wire from the alternator to the starter with a larger one as well.
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Suggestion
I wanted the extra 3� to run the short cable more cleanly thru the bay.
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Suggestion
A better solution is remove the factory shared circuit, and run two separate circuits from the jump-stud, a 2 gauge cable to the starter, and a 4 gauge cable to the alternator.
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Suggestion · Original poster
Lift the cable off the lug and install one end of the 24" cable onto the alternator lug (exiting out the upper notch), put the factory cable back on (lower notch), and tighten nut.
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Suggestion · Original poster
Next back off the upper alternator bolt (15mm or E12 torx iirc), once it is backed off a fair bit, you can strike the socket, or use a brass drift, with a hammer to give a few good whacks to the bolt.
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Suggestion · Original poster
I opted to use a red cable simply for the sake that if someone besides myself is working on the car in the future, and sees an aftermarket cable, Red is the universal symbol for positive and it is less likely for a problem to occur, since black is universally ground.
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I can't say I'm ever on the 996 board, but just figured I would make a post over here.
I fix more so the older model Porsches but do fix the odd newer one as well.
For those of you with 996s who have cars where the volt meter sits right around 13V when the engine is hot, you might consider an upgrade.
There are a couple of faults with the charging system on the 996s. The first is that the wire from the alternator to the starter is very small, around a 10 gauge. Not nearly enough. Then the engine to chassis ground seems to build a bunch of resistance as well.
So here is an easy fix to this situation which will allow you to get proper charging out of your system.
Go to the auto parts store and buy 2 4 gauge battery leads with eyelets already on them. 1 should be 24" long, the other 16". They should look like this
I went with red for the 24, and black for the 16.
First disconnect battery
Remove the airbox, and take the serpentine belt off the alternator pulley (24mm socket for belt tensioner).
Next back off the upper alternator bolt (15mm or E12 torx iirc), once it is backed off a fair bit, you can strike the socket, or use a brass drift, with a hammer to give a few good whacks to the bolt. This will aid greatly in manoeuvring the alternator, and reinstalling. Once done, remove the upper bolt (with idler roller), and lower alternator bolt.
Now rotate the alternator clockwise, then pull the alternator rearward.
It will only move out a small amount, then you can tilt the top down.
You can then use a 13mm wrench and undo the nut retaining the alternator charging cable. Notice that it exits out the lower of the two slots.
Lift the cable off the lug and install one end of the 24" cable onto the alternator lug (exiting out the upper notch), put the factory cable back on (lower notch), and tighten nut.
Now feed the 24" cable in to the engine and snake it behind a few pieces and under the hydraulic fluid reservoir, and the supply line to the AC compressor.
Reinstall the alternator, installing the upper bolt with idler.
On the lower bolt, add one end of the 16" cable to the lower alternator mounting bolt.
Once the alternator has been fully mounted attach the other end of the 24" cable that you snaked through the engine to the jump post.
Then attach the other end of the 16" cable to the easily accessible bolt for the motor mount.
(don't mind the coolant, waterpump let go, and just had to swap it out)
Reinstall the serpentine belt, and airbox.
Reconnect the battery.
Start the car.
When cold you will likely see 14.2V on the voltmeter, once warm, it will be around 13.7V but never dip below that.
I hope this helps a few people out.
If you need more info, or are in the Vancouver BC area and want the mod done, PM me as I am not on the 996 forum much, and doubt I will check this post very often.
Great idea! I'm replacing my alternator/starter cable again. It failed again after a year and it's already the upgraded version (thicker). I lost 0.7v between the alternator and the positive jump start terminal above the a/c.
Will consider your mod if the new cable fails again in the future. Do they carry black for those size/length? You could even zip tie it along the original starter cable to make the install even cleaner.
Yup, they did. There is actually a TSB on the issue. I had the cable fail and of most concern is that the supposed updated cable was the same part number as the one that failed. Nothing is perfect.
Come to think about it, I do have some concern of the mod. the factory starter cable has a fat wire going from the jump start terminal to the starter then a thinner cable from the starter to the alternator.
When everything is good the starting current (200A+) goes through that fat wire to the starter. Once the car started, the current goes from the alternator to the thinner wire then the fat wire then to power distribution.
If the fat section fails (like in my case), everytime you start the car, the starting current will go through the red wire from the jump start to the alternator then to the starter via the thinner factory cable that's designed only for ~120A. Either the starter will turn slow which you will notice or the thinner wire just get overloaded without you noticing.
This mod will actually help prevent the factory cable from failing nearly as fast.
The reason is that there is now a secondary path for the voltage to come through, giving a slight relief to the single factory wire currently in use. The slight relief of say 50amps will drastically increase the life of the main wire.
If one were so inclined they could reach in with the alternator removed, and add an additional cable from the starter to the jump post helping to reduce the strain further. Or replacing the small wire from the alternator to the starter with a larger one as well.
As stated there is a TSB on this.
Porsche like everyone else is not above making mistakes. More new vehicles have problems like this than the older vehicles as everything is built closer to the edge to conserve costs, and weight.
If you think they are above error, how about that IMS, or the liners on the early boxsters, or how the 996TT seems to pop out of second gear around 60k miles requiring a full rebuild on the transmission. Or the plastic coolant pipes on the cayenne. The list goes on. The point is no one is perfect, and doing small things like this only improves the car and helps to remove faults.
Yes they carry them both in black or red.
I opted to use a red cable simply for the sake that if someone besides myself is working on the car in the future, and sees an aftermarket cable, Red is the universal symbol for positive and it is less likely for a problem to occur, since black is universally ground.
What you said is true if the original cable has not failed yet. My point was if the original cable from the jump start terminal to the starter has failed already, this mod will help the alternator voltage but will also add stress to the thinner original cable whenever you crank the engine.
This is a great fix. I was suffering from low charging also on my 99 Cab.. Got a couple of cables and completed the connections as described - back to full charging. About a 30 minute job - the only PIA is getting the alternator out and back in. A little patience & determination and you 'll be back in business.
Thank you for sharing the info.
I agree with this 100%. Porsche uses a minimum wire diameter for load requirements, also wire routing is minimized my sharing common cables all which saves a LOT of weight. Minimum weight is extremely important to Porsche, so the risk of problems when things are not at optimal conditions are imminent.
As to the starter/alternator cable sharing, the crimp/solder splice at the starter is a weak point. A better solution is remove the factory shared circuit, and run two separate circuits from the jump-stud, a 2 gauge cable to the starter, and a 4 gauge cable to the alternator. This would add a few grams/ounces weight but would carry more current and eliminate the weak crimp connection.
The additional ground cable from the alternator mount bolt, to the motor mount bolt is also a good idea.
�Does anyone one have pics of these upgraded/improved cables?�
The cables are standard dual lug ones found at any auto parts store. I put colored tape on each end for ID. The only mod I did for this was anchoring a 19� cable to one of the SAI pump bracket bolts. I wanted the extra 3� to run the short cable more cleanly thru the bay.
19� cable from lower alternator mounting bolt to SAI bracket.
24� cable from upper notch bolt on alternator to jump post.
