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Discussion summary
YOUR RESEARCHBattery warning light.....again
Leading reported evidence
Replace starter and y cable due
Performed · outcome unconfirmed
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Performed · outcome unconfirmed · Original poster
A few months ago I had replaced the starter and y cable due to a hot slow start.
Leading evidence: 'Replace starter and y cable due' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'same' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check b+ terminal (large red wire)' (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
ugh....I replaced the voltage regulator on my old alt 4 years ago.
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Suspected cause
Just looked up the 996.1 wiring diagram, I do not know what you have but imagine they are probably the same.
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Suggestion
Here is the alternator, you definitely want to check the B+ terminal (large red wire) to ensure it has battery voltage at all times.
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Suggestion
If you don't have any voltage there, then go X59 connector (I assume this is in the engine compartment quick disconnect) and pull it apart and check pin 12 for voltage with the ignition on, this would be on the passenger compartment side of the connector.
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Suggestion
If you don't have any voltage there, then go X59 connector (I assume this is in the engine compartment quick disconnect) and pull it apart and check pin 12 for voltage with the ignition on, this would be on the passenger compartment side of the connector.
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Alright...so...
-new starter
-new y cable
-new alternator
-new battery
Track day friday....light comes on. Park it to cool down and it wont start. Had to boost it to get home.
A few months ago I had replaced the starter and y cable due to a hot slow start.
Battery light started coming on then, so I replaced the alternator shortly after (maybe a week)
The car never charged over 13V after replacing the starter and Y cable. Got warning lights so I changed out the alt. Car still never charged over 13V but it never gave me the warning lights after that.....until Friday.
Sounds like you don't have a +12 VDC to the field of the alternator. Does the battery voltage EVER increase after starting the car or is it always low 12's or 11's? I.E. do you think the alternator has any output?
Starting checking different voltages. And then have someone do a load test.
Check voltage at the alternator directly. If 14v, then check voltage at the battery. Maybe there's a problem with the hot side (red power cable).
I've seen replacement batteries go bad, or at least they are bad to begin with.
Just looked up the 996.1 wiring diagram, I do not know what you have but imagine they are probably the same.
Here is the alternator, you definitely want to check the B+ terminal (large red wire) to ensure it has battery voltage at all times.
Here is the rest of the diagram that goes to the instrument cluster, it connects on the right, "K157, Generator":
If it does, measure the L terminal, which would be the 1.0 mm Black wire. I am not sure exactly what this does, if it supplies power to the alternator for the field, it is also tied into the ABS, ASR and PCM (I assume this switched power for the field). But check the voltage there. If it is for the field, then it should be switched +12 VDC. If you don't have any voltage there, then go X59 connector (I assume this is in the engine compartment quick disconnect) and pull it apart and check pin 12 for voltage with the ignition on, this would be on the passenger compartment side of the connector.
Those are some good first steps. It sounds like it will be easy to figure out.
The only other thing to check is continuity between the alternator body and ground to ensure you have a ground path.
When the regulator on my alternator was going bad, the symptoms were the same as what you're describing.
Start the car and the voltage would be ~13V. Drive for 10 minutes and it would start slowly dropping, eventually getting as low as ~11V. By that time, the warning light would come on and I would start getting error messages on the dash for ABS and some other things. Eventually the car would stall because the ECU can't run on a voltage much lower than that.
I got a new regulator for about $40 from Pelican and replaced it, keeping the alternator otherwise original. Ever since then, I'd start the car and would see 14V and it barely gets lower than that.
Did you swap the alternator yourself? If you had a shop do it, is there a chance they put in a new alternator but re-used the old regulator? Here's my old and new regulators side-by-side, note the difference in brush length:
I did all the work. new alternator with new reg. I've done this job about 4 times now. ugh....I replaced the voltage regulator on my old alt 4 years ago.
thinking of taking the reg off my old one and putting it on the new Alt.
I only have one question. What exact alternator brand and model you put in?
My guess is it's your battery or the alternator. If your battery checks out fine (load test), I would check the output of the alternator at the back of it (use a stiff insulated wire. Form a hook with some metal exposed and poke at the back). It should be about 14.5v at cold start and about 14v when fully warmed up. If not, you need to replace the alternator. You should have some warranty on it, right?
Yeah. ...I'm wondering that since the battery was killed when I did the y cable, it was never able to recover and that's causing my issues??
Bosh, 3 year warranty.
Yeah, you may very well have a dead/intermittent cell in your battery. One way to confirm is to test it with a tester (load based or capacitative based). If the battery measures less than 12v with car off, most likely your battery is toast.
If it's a Bosch brand new, it's less likely to fail but if it's a Bosch reman, it's not uncommon to fail out of the box.
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