Failing Alternator? 987.2

Hi everyone. Over the weekend, my car (2012 987.2 Cayman ) had trouble starting where all the electronics came on but the engine wouldn’t turn over. I don’t think I even heard the starter clicking. After a few tries it would start. Then on Sunday, it started fine, but the headlights would dim a little as the rpm dipped slightly in the first min of warming up. I immediately turned it off and took the other car. I should also note that I saw a “Warning battery /generator” error a week ago, but it went away on the next startup so I didn’t investigate further. After some research, it looks like this is a failing Alternator . Can anyone weigh in with other things I should check before replacing the alternator ? Has anyone replaced the alternator in a 987.2 or 981 engine? I think the factory maintenance manual calls for lowering the engine for this. I’ve seen a video where someone replaced it without dropping the engine, but wanted to see if anyone had experience with this. It’s a tight fit, but seems doable w/o engine lowering. It looks like Bosch offers a remanufactured alternator with the part number AL0898X so I’ll probably be doing that. I saw another thread on here where it was said that the remanufactured units are 99% new.

How old is the battery and what is the current mileage?

Definitely need an output test of the alternator . Sounds like it’s not putting out the correct charging voltage.

Verify Alt or Batt before doing anything.

The battery is less than a year old, but I had to have it recharged a few months ago after I got back from a vacation. I thought the parking mode on my dash cam was draining the battery , but I suspect it's something else. It has somewhere around 140650 miles.

How does one do an output test?

With the car idling, warmed up and all accessories including lights off, get access to the battery terminals and place a volt meter on them and read the output. Should be between 13.8 and 14.2 volts, that would indicate correct voltage at idle, should be the same as well at all RPM's. Electrical loads such as the headlights etc being on will reduce the output esp at idle, If you see a big drop the battery may be suspect and below normal charging capacity and you may want to put a load tester on it. A bad battery will cause charging issues and may trip the CEL light... Even if your battery is nearly new a period of discharge if long enough can cause sulfation of the plates and a decline in capacity or even a dead cell. Some smart chargers have a "fix" where they go into a variable pulse high voltage/amperage charging mode which helps to renew the battery by shocking the sulfation off of the lead plates and revert back it back into solution as sulfuric acid.

After warming up the car, I let it idle with almost all the accessories off: I saw 14.95-14.98 at the battery . (I wasn’t able/didn’t know how to turn off the fog lights or head unit). Then I turned a bunch of accessories on ( headlights , both seat warmers and ventilation, and AC): I saw 14.65 at the battery . Both readings are higher than the 14.2 benchmark; does this indicate a charging issue? For a few min after turning the car on, the lights would dim with slight drops in RPM. It also wasn’t as steady of RPM as I’m used to. After warming up, the lights and idle RPM were steady. No increased brightness on slight revs either.

You didn't say (or I missed it) if you followed Boris' advice to get that battery load-tested. It's free and only takes a few minutes at a car parts store. Since it already failed after setting during your vacation, it might have been damaged. Check the simple things first before going down that rabbit-hole. Testing the voltage from the alternator only makes sense when the battery is healthy. It it checks out OK, or even if it doesn't, put it on a good battery maintainer with a "recondition" mode and leave it for at least 8 hours. Then do your alternator voltage test.

Reading your latest post, with the added info, your best bet is to get the battery load tested. Some of the observations you made definitely indicate an ongoing issue, but a faulty battery can skew the other results. My research has found slight variations in what an alternator should produce, with some claiming 14.5 volts as being normal, but your readings of nearly 15 volts seems a tad high. Also, you mention the lights dimming slightly with lowered rpm’s. A correctly working voltage regulator , built into the alternator , does just that. Regulates the voltage no matter the rpm’s. But all of these factors depend on a healthy battery . Start with the battery load test, then if that checks out, it’s time to delve deeper into the alternator integrity.

Also to note. If you don't have access to a load tester and want to do a quick cell check try driving the car for a while and when finished immediately disconnect the negative terminal from the battery and check the voltage and record it (don't reconnect ,yet). After a period of hours or a day or so check the battery again and note any decline in voltage. Results will vary with temperature fluctuations but a good battery should always show 12.8V or slightly better without any draw for at least a few weeks (our cars are constantly drawing "parasitic" currents even when off). If it shows 12V or less then there is an issue with it, likely a bad cell. If possible check the electrolyte levels in all the cells and top up with distilled water if low. If you found some cells low on electrolyte then repeat the test. If your alternator is faulty and charging high then it will be plausible that the battery will have depleted electrolyte as the overcharging condition causes boiling/ evaporation.

I had the battery load tested at autozone and it was in good shape- “green lights across the board”. I should note that I didn’t see the issue today when I started the car to go get the test. I haven’t driven the car since the issues starting it over the weekend. I only started it a few times and warmed it up last night to test voltage with accessories on and off.

I’ve discovered that the issue starting my car, may actually just be me pressing in the clutch 99% instead of 100%. This seems more finicky than previous, but I’ve been able to start the start without issue consistently when I make sure to bottom out the clutch. There’s like 1 more inch left that I wasn’t doing a few times that just turned the accessories on. I want to investigate this more. Maybe the switch that signals the clutch is depressed when you’re turning the key is wearing out. I disconnected the parking mode fuse tap for my dash cam and will be able to let the car sit for a few days to see if any issues arise again. Looking through maintenance records, I discovered that the alternator was replaced (with the correct Bosch part, AL0898N) about 9 months before I bought the car. It’s only been just short of 2 years on this alternator ; not sure why the voltage regulator would be an issue on a 2 year old alternator . I want to see if the "light dimming with rpm changes" issue returns before considering replacing it again.

I haven’t seen the 'light dimming w/ rpm changes' issue since disconnecting the parking mode on my dash cam . As for the car not starting, it's definitely the clutch switch. I have a new one sitting on my desk (part #997.613.109.50) and will install it soon. I’m going to continue to look out for the issue, but I think it was the dash cam ’s parking mode causing problems.