16 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHPositive Battery Wiring
Leading reported evidence
Replace dreaded y-cable and the engine ground strap
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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Performed · outcome unconfirmed · Original poster
On a related note, I have a tested alternator and put a new regulator on it and I also replaced the dreaded Y-cable and the engine ground strap.
Leading evidence: 'Replace dreaded y-cable and the engine ground strap' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'alternator/regulator is bad' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check battery cables' (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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Performed · outcome unconfirmed · Original poster
On a related note, I have a tested alternator and put a new regulator on it and I also replaced the dreaded Y-cable and the engine ground strap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
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Suspected cause
If it reads lower than 13.8v, most likely the alternator/regulator is bad.
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Suggestion
I would do as Ahsai recommends and check your voltage drop.
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Suggestion · Original poster
I haven't had time yet to run Ahsai's tests (weekend project), but my cluster volt gauge is reading a 11 with the car not running (key turn to the right).
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Rennlist: 1 discussions
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So my battery is not charging very well these days and before I go out and buy a new one (which I will probably do anyway), I want to make sure that there is a good connection from the alternator to the Battery. I thought I read somewhere that there is a distribution point somewhere under the car between the back and the front but I could be mistaken. If there is, I'd like to clean it.
Does anyone out there understand the Battery connection from the back to the front of the car?
On a related note, I have a tested alternator and put a new regulator on it and I also replaced the dreaded Y-cable and the engine ground strap.
TIA
To pinpoint the culprit, you can do the comprehensive voltage drop tests I wrote about that cover the alternator, battery and all cables. For less work, you can check the battery cables. Make sure the positive one bolts tightly to the distribution box on the firewall and the negative one bolts tightly to the chassis.
What does your voltmeter in the cluster read?
This shows the power distribution cables
http://www.autoatlanta.com/porsche-p...section=902-05
There are several connection points between the alternator and the battery on the 12V positive side. One being in the engine bay where the Y-cable connects, one under the car, one on the power distribution box. Also the main lead from the + battery post to the power distribution box. I would do as Ahsai recommends and check your voltage drop. Could be you just need a new battery.
You have a problem for sure. The quickest test is to measure the voltage drop between the alternatit output (the output lug at the back of the alternator) and the battery. Anything greater than 0.3v, some of your positive cables are bad. They connect just like Joe described.
Then measure the voltage at the alternator lug. If it reads lower than 13.8v, most likely the alternator/regulator is bad.
I haven't had time yet to run Ahsai's tests (weekend project), but my cluster volt gauge is reading a 11 with the car not running (key turn to the right). Does this accurately represent the voltage across the battery (obviously a problem)? Where is the cluster volt gauge taking its measurement from?
OK I took some measurements. Only at the Battery (from terminal to terminal) and at the positive Jump point (jump point to body of car) in the engine bay for now.
All measurements were effectively the same in both places, which I guess means there is no resistance between the engine bay and the battery, which seems good.
Car off: 11.97 Volts
Car on (not running): 11.3 Volts
Car on and running: 13.3 Volts
To measure voltage drop, you want a lot of current going through the cable that connects the two points you're measuring (V=I x R). e.g., if there was no load (current) at all, I=0 and V will be 0 despite a high resistance R. That's why I specified the low beam and a/c load in my write-up to add tens of amps to the load. Without those, the engine will only draw about 20A when running so voltage drop may not be as obvious.
Having said that, the fact that you measured only 13.3 at the positive jump start terminal in the engine bay points to a weak alternator or bad Y-cable.
So I charged the battery overnight (9 hours with a 900mA trickle charger).
The battery was at 12.58 Volts after the night on the trickle
Started the car, turned on AC/lights/seat heaters and read:
13.1 at the Battery and 13.3 at the Jump point (roughly)
Turned off the car, kept all the stuff still on and read:
11.44 at the Battery and 11.39 at the Jump point
Thanks Ahsai. I guess I will go with the Bosch Platinum Series AGM Battery Group Size H7/L4/94R.
Could a bad cell be bringing down the Alternator voltage to 13.3 Volts? I'll measure the Voltage after the new battery is in and see if it goes up.
BTW it looks like the current battery is about 6 years old.
