I am trying to diagnose a slow crank/no crank. My 2008 G37 went into limp mode yesterday while leaving a stoplight. ABS and slip light came on the dash. Didn't see any battery light. Battery tested fine but needed a 30 min charge in order to pass the test. While diagnosing today, my voltage dropped to 11.7V while idling, so I decided the alternator was bad. But then I found that these cars have a variable charging system and they can drop as low as 11.4V.

I'm 90% certain that my alternator is still bad, but is there a sure fire way to test it without removing it? I really don't want to do this job if it's not necessary. See attachments for the reference materials. Thanks.

 

Disconnect the harness connector from the battery current sensor and the system should "fail-safe" to charge constantly at 14.4V+/-. This link shows the current sensor.

 

So, I disconnected that harness, and im getting a steady charge at 14.3V. So, do I still have a bad alternator? Or is there another part of this circuit that can go bad? Perhaps this sensor itself maybe?

 

That tells me that the voltage regulator in the alternator appears to be doing its job. This does not mean it is not starting to fail. If the battery is fully charged and the engine is slow to crank then you have to look at the starter (and related wiring connections) or a parasitic drain on the battery. The wiring at the starter is known to corrode over time.

I would reconnect everything, ensure the battery is fully charged, then get a multimeter and check for parasitic draw. After the car "goes to sleep" (after ≈30min. or so) you should be reading ≈25-30mA (milliamps) on the meter. Anything more and you have something draining the battery. A dying alternator could be the culprit in that case.

 

So, I let the car heat soak for about 10 min and came back and ran the same test again. This time it failed to charge. I was right at 11.7V with the system bypassed. I'm now pulling the alternator. Smh.

 

Was out yesterday and my battery and brake light came on. Had enough battery power to get the 16 miles home. Hooked up the scanner to the obd2 and the battery isn't getting charged when the car is on. How hard was it to replace the alternator? It's hot and I really don't feel like getting under the car to change it. Mobile mechanic says $565 parts and labor. Haven't heard from the dealer but if it's under $700 i might just go that route.

 

So, my guess is that your mobile mechanic is quoting you a remanufactured alternator if he can do the job for $565. This is not a fun job at all and over the years, I've lost much faith in remanufactured electronics. I'd say that no matter who does the job, go with a new alternator, even if it's aftermarket. The price on the new Optima from my local parts house is $363.

I consider myself a pretty solid shade tree mechanic, but I would've preferred not to do this job. But I'm also a cheapskate and I hate paying guys $125+ per hour whose work is rarely to my standards. I believe this job at the dealer is $800-900 if I remember correctly. If you trust your local mobile mechanic, I'd have them do it. But I would stand firm on replacing it with a new unit. If you decide to do it yourself, I'd recommend that you watch it on youtube. It will show you what the job entails. Pulling both air boxes, radiator fan assembly, oil filter, possibly the sway bar, etc. I'm about an hour into the job in my garage and I don't have the alternator off just yet, but I'm finally down to it. Hope this helps.

 

Not sure how helpful this may be, but I recall a fellow forum member found that by unbolting the power steering pump and moving it out of the way made for much easier access to remove alternator.

 

Well I called around. Prices are parts and labor after taxes and fees. Goodyear Auto said $594, 2 year or 24 thousand mile warranty. Dealer said $950 or if I bring the part they would charge like $300 labor. What would y'all do?

 

Mummy, I'd say it really all rides on who you trust to work on your car. This is a job for a detail oriented mechanic who is willing to take his time and not snap an ear off a plug or the small bolts in the back of the factory bracket. Trust is the most important thing. Read reviews of the place you choose to take it. I was considering having the oil gallery gaskets replaced on mine, but with a teardown that is so detailed and delicate, I'm having a hard time even trusting the local Infiniti dealer. I spoke with the head mechanic at length, grilling him about his knowledge of this job and he seemed to be quite comfortable taking it on and seemed to know his stuff. I still haven't decided if I want to spend a week doing it, or cough up the $1200 for the dealer to do it.

Hope this helps. Good luck making your decision.

 

I ended up going to Goodyear. $594 after tax. Saw Youtube videos and the job looks pretty simple actually, if you have a lift that is. The dealer changed the price on me when I actually took my car there. Roughly $1450 for the Alternator. $650 for the part and 4 and a half hours labor at $185 an hour. And tried to tell me I needed a new battery. They wanted $300 for theirs. Made my choice to go elsewhere easy.