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I recently replaced my alternator with a bosch unit after getting constant battery lights in the G due to what I assume at the time was a dead alternator. Now I'm back to square one with the NEW alternator not charging also:
- car sat for about 2 weeks and now the new alternator is not charging again (confirmed via multimeter at the alternator output post)
- all breakers checked, including the batter fusable link, all appear to be fine / show good continuity. I also checked the 2 fusable links in the fuse box next to the batter.
- battery light is on the dash, as expected since alternator is not charging
- battery light shuts off above ~3k rpm when revved, but when I put a multi meter to the battery charge don't see a voltage bump when revving.
- I checked continuity between alternator and battery and all seems fine
- my batter is actually relocated to the rear of the car, but the voltage drop I'm seeing is <0.05V
Does anyone have any idea? I am afraid that perhaps the bosch alternator went to hell, but its hard to believe considering it was in for only a couple weeks and it would die when the car was sitting for 2 weeks. Just seems unlikely.
also I should note, all my interior lights are working and so are the dash lights and I DO have a brake light on. I know this is a common sign for a fuse link issue, but I checked the fusable links and they all appear to be ok. Is there a particular procedure for checking them??
Last edited by Row2K; 09-10-2020 at 09:12 AM.
Reason: correction: I do have a brake light on
Figured I'd give a troubleshooting update so that others who come across this thread may be able to better track down their issues. Where I stand right now:
- brake and battery lights are on
- continuity between B terminal (large heavy gauge positive terminal on the back of alternator) and battery verified all the way to the trunk. Voltage drop between B terminal and battery in the trunk is <0.05 V
- Alternator connector (number 3 in diagram below checked):
Here is where things get interesting:
Alternator connector (connector 3) is a two post connector, see image below of old alternator:
These two posts go to the battery and the ignition system :
- I was able to verify that pin 4 is supplied with battery voltage (~12.3V in my case at the time of testing) and pin 3 is at 0V when ignition is OFF
- When ignition is ON, pin 4 is supplied with battery voltage (~12.3 V ) and pin 3 is at ~11.1 V.
This means that the two pins which are supposed to supply the electromagnets in the alternator with power to "turn the alternator ON" have a difference of ~ 1.2 Volts.
I am not sure if this difference between these two pins is normal. Can anyone confirm if this is normal or if both pins to the alternator should be exactly the same voltage ???
Next I started looking into the grounding situation and just to be sure began by adding additional grounding to the block (and in turn the alternator). So I added a temporary grounding cable to the block where the old grounding cable was for the battery:
This additional ground has made no difference, but I will add another ground to the alternator body directly tomorrow and also another ground to the trunk mounted battery tomorrow to see if there is any difference.
So right now it looks like my new BOSCH alternator took a **** after about 1 month of use and unless there is something to the difference in voltage on the #3 connector pins (ignition on: one supplies 12.3V, other pin supplies 11.11V to the alternator) then I'm out of luck and it looks like the alternator needs to be replaced....again
Assuming the Bosch alternator works like the OEM version, it looks like your alternator is bad. From my 350Z Service Manual, pin 3 on the alternator should either be at ground (alternator not charging, light on) or open (alternator charging, light off). What part number Bosch alternator did you buy?
Assuming the Bosch alternator works like the OEM version, it looks like your alternator is bad. From my 350Z Service Manual, pin 3 on the alternator should either be at ground (alternator not charging, light on) or open (alternator charging, light off). What part number Bosch alternator did you buy?
Hi Karlt, alternator is the Bosch AL2399X. Im afraid you are likely right. The alternator worked well for about a month and then gave up the ghost when I picked the car up from a body shop. The body shop had to do some welding to fix a rust spot I found and I fear they didn't ground the vehicle correctly during welding and potentially damaged some susceptible electrical components (I also found that my window motor stopped working upon picking the car up).
I will also check and see if pin 3 on the alternator is showing ground continuity per the the following test from the manual as I have yet to do this:
Based on my understanding of this test if pin 3 in plug F20 (alternator connector) is grounded then the charge/battery warning lamp should turn on and thus if the alternator is showing ground/providing this ground in pin3 the alternator is likely bad.
Just wanted to clsoe out the thread and provide an update to anyone doing their own alternator troubleshooting.
I was able to get a replacement BOSCH alternator through the original seller who replaced the failed one under warranty. After installation everything is back up and running; no brake light, no battery light, and no issues.
That being said for anyone going with an aftermarket alternator please verify that your seller is an authorized retailed for the brand. I say this because when I called up BOSCH tech support they basically told me to shove it and to process my warranty claim through the seller. So please please please folks; before you purchase make sure that your seller can replace the part under warranty. I got lucky and mine did, but I should have checked before purchasing.
Happy troubleshooting to all. I'm back on the road
Thank you so very much right now I am having the same problem. I just bought a BOSCH Alternator from NAPA AL2399X the other (2) I had the guy put on the same problem you were having I too had the same problem. After (2) Aftermarket Alternators and now BOSCH let me see what happens. It is in the shop now. I will see tomorrow and update you but I needed this feed for information on what I needed to do. I will read your comments. But I am having the same problems. 2005 Roadster ugh... Killing me with Labor cost. NAPA gives you a Lifetime Warranty on the Alternator.
My comment was basically that it's rare for a new Genuine Bosch unit to fail so quickly. I was curious if it was a remanufactured unit.
I also wanted to add that I plan on rebuilding my alternator soon. I already have the replacement parts. I'll be rebuilding a Mitsubishi OEM unit that came with my 06 350Z. Only recently I noticed some slight bearing noise coming from it, otherwise it's working fine. Rebuild kits are very affordable/cheap when compared to purchasing a new OEM unit. The common component failure in an alternator is typically the voltage regulator or brush assembly. Usually these two pieces are sold together. The next most common failure are the bearings, more often seen on aftermarket or remanufactured units. Many years ago, auto repair shops would rebuild alternators since it was cheaper, however due to labor cost increases, it's now cheaper to simply replace. Generally, you don't need specialized tools to rebuild an alternator, but a press or bearing puller kit can make it easier (depending on brand/design). I'll be replacing the bearings, voltage regulator, and brushes. I also purchased a new slip ring, but this may not be required.
In general, the coils/windings and diode bridge in an alternator don't fail or at least it's very rare. You would need to soak the unit in water to short it or stripping the varnish protecting the coils which would also result in a short. I've also heard of small bolts, nuts, and/or screws being dropped into an alternator and causing chaos upon startup.
I'll try to document the process and post about it on the forums. I like the idea of keeping the original alternator in my Z, partly because I think it's cool to maintain the Nissan/Mitsubishi markings, but also because I simply don't trust aftermarket and in some cases, remanufactured parts. Lastly, it's affordable if you provide your own labor; even with high quality replacement parts, I think I spent less than $80 on everything. I have had good experiences with remanufactured Denso/Hitachi starters and alternators from RockAuto & Napa, but I'm picky about *where* (which country) the part was rebuilt in. Also of course, look closely at Warranty/Support terms.
My comment was basically that it's rare for a new Genuine Bosch unit to fail so quickly. I was curious if it was a remanufactured unit.
I also wanted to add that I plan on rebuilding my alternator soon. I already have the replacement parts. I'll be rebuilding a Mitsubishi OEM unit that came with my 06 350Z. Only recently I noticed some slight bearing noise coming from it, otherwise it's working fine. Rebuild kits are very affordable/cheap when compared to purchasing a new OEM unit. The common component failure in an alternator is typically the voltage regulator or brush assembly. Usually these two pieces are sold together. The next most common failure are the bearings, more often seen on aftermarket or remanufactured units. Many years ago, auto repair shops would rebuild alternators since it was cheaper, however due to labor cost increases, it's now cheaper to simply replace. Generally, you don't need specialized tools to rebuild an alternator, but a press or bearing puller kit can make it easier (depending on brand/design). I'll be replacing the bearings, voltage regulator, and brushes. I also purchased a new slip ring, but this may not be required.
In general, the coils/windings and diode bridge in an alternator don't fail or at least it's very rare. You would need to soak the unit in water to short it or stripping the varnish protecting the coils which would also result in a short. I've also heard of small bolts, nuts, and/or screws being dropped into an alternator and causing chaos upon startup.
I'll try to document the process and post about it on the forums. I like the idea of keeping the original alternator in my Z, partly because I think it's cool to maintain the Nissan/Mitsubishi markings, but also because I simply don't trust aftermarket and in some cases, remanufactured parts. Lastly, it's affordable if you provide your own labor; even with high quality replacement parts, I think I spent less than $80 on everything. I have had good experiences with remanufactured Denso/Hitachi starters and alternators from RockAuto & Napa, but I'm picky about *where* (which country) the part was rebuilt in. Also of course, look closely at Warranty/Support terms.
Cheers!
-Icer
When I pulled out the old alternator I tried to disassemble it just to see what it looks like on the inside. To be honest I found it rather difficult. The housing was not only bolted together, but thoroughly oxidized and press fit together. If I recall correctly I ended damaging it quite a bit just trying to take it apart. If you do manage to disassemble and rebuild please document the process. Kind of interested to see what exactly is on the inside and/or what needs to be replaced.
I got my car back today after they put on the New Bosch Alternator I had under warranty with Napa. But I had to upgrade to Bosch after 2 times attempting their aftermarket Alternator that I had bought earlier from them and they did not work kept reading defective. After replacing the aftermarket Alternator 2 times. But Napa testesd afterwards and here is their reading Load off was 11.83 V (Low) Load on 11.792 V (Low) Diode Ripple was 0.10V Normal. Already had bought a New battery a couple of months ago. Will update you if anything occurs. 🤔 geesh troubleshooting is something else guys if it is electrical. Always get OEM parts if electrical has been my thing to do in replacing parts. Thanks everyone ☺️
Yes, splitting the case can be difficult depending on the state of oxidation/corrosion. These things are assembled with very tight tolerances. You just need to be patient and work it slowly. Sometimes the rear shaft bearing is the root cause. I'll find out in the coming weeks. I've got multiple car projects for family I need to tackle 1st.
Cheers!
-Icer
09-09-2020, 02:39 PM
New alternator not charging
