JediRob1

Greetings all, I'm hoping you can help me diagnose this problem. I searched but didn't find anything that matched all my symptoms.

First, I started getting an intermittent battery light a few days ago. Then Friday morning I got a CEL, but no battery light. Stopped by Autozone on my way home to have them check the CEL code; they said it was P0850 - neutral switch. Friday evening, CEL disappeared but the intermittent battery light came back. Saturday morning, CEL came back, along with the battery light. Both stayed on this time. On my way back home, pretty much all the rest of my warning lights came on, followed by a loss of power steering and almost everything electrical (radio, windows, headlights, etc.). After I got home, I popped the hood and looked for any obvious loose connections or anything like that. Didn't see anything. Speculated that my battery was dead, so I tried restarting the car, and sure enough, dead battery.

Could a faulty neutral switch cause all this? With the battery being drained, my first thought was the alternator, but I just replaced that a couple months ago. I haven't had a chance to check the alternator's voltage output yet; will be doing that later today.

Thoughts? Thanks for your help.

Jon316G

iTrader: (1)

When you replaced the alternator, did you get an OEM or aftermarket/refurbished one?
We've seen people purchase non-OEM units and have problems where the it doesn't charge above 14V and causes problems.
Though some have purchased theirs from Autozone and reported not having issues.
So measure the voltage and report back...

yiksing

Maybe it was the weakening battery that causes the neutral switch, etc to start throwing CELs.

VOODOO8

My guess would be two issues happening simultaneously. 1st issue = dead battery. 2nd issue might be a defective neutral switch. Agree with yiksing that the bad battery may be the cause for the po850 CEL, so check the battery first and replace if bad. Once you have reset everything post a new battery install (check posts here about new batteries - you need to shop carefully to get one that is both the right size and the right capacity), see if your still getting the CEL. If so, then replace the neutral switch.

JediRob1

Thanks everyone for your help. The mystery continues...

Hooked the charger up to the battery and the battery appeared to be just fine. Tried starting the car and it started right up. Checked the alternator, and it was putting out around 14.4V. Checked the battery and it was holding a charge and working just fine.

Car was running fine but the CEL was still on, so we went to Autozone to check the code again. Still just the one code--P0850. Restarted the car and the CEL was gone (the Autozone guy may have cleared it, not sure). Drove around for a little while and had no problems. No CEL, no battery light, nothing. Car seemed to be just fine. Got home and the alternator and battery were still fine. We checked all the electrical connections we could easily find, and there were no obvious problems.

This morning on my way to work, it was working fine. Stopped for coffee, and after I restarted, the battery light came on for just a couple seconds, then went back out. That was it. There were no other problems or indications of any problems.

I'm stumped on this one, as is my bro-in-law, and he knows much more about this stuff than I do. It seems unlikely that an intermittently faulty netural switch would cause all this, but I don't really know much about it. Any other thoughts on likely culprits? Is it possible the PCM is flaking out?

Thanks again everyone for your help.

laythor

if it's the OEM battery have you checked the fluid level?

Jedi54

iTrader: (7)

Never fear, Jedi is here!

I agree that it sounds like there are two issues here that are ocurring simultaneously.
1. neutral switch. (wasn't aware this threw a CEL, mine didn't when mine went bad)
2. issue with the system charging.

hearing you describe all the warning lights come on and PS going off is exactly what happens when the alternator goes out and the battery is struggling to power the car. as the voltage keeps dropping the car begins shutting off certain components. My PS went off after I dropped to about 9 volts.
My fix: new OEM alternator and I haven't had issues since.

seeing as how you replaced your alternator I would normally rule that out but if it isn't an OEM, it could be causing problems as Jon mentioned others have had problems with non-OEM units.

I dont' think it's the PCM flaking out.

JediRob1

Thanks again everyone for your help. Last night I was finally able to catch it while the problem was occurring and test the alternator's output while the battery light was on. Sure enough, it's the alternator. Luckily I wasn't too far from home; I had a repeat of last weekend's "cascade failure" and once again got to enjoy my dash lighting up like a Christmas tree as all my systems started shutting down.

So the next question would be, where's the best place to get an OEM alternator? Onlinemazdaparts.com? Mazmart? Someplace else?

Thanks, everyone.

Jon316G

iTrader: (1)

http://blackhaloracing.com/products-...-8-alternator/

Easy_E1

iTrader: (2)

We have new alternators right here in Phoenix. Just let me know and we can hook you up and install it too.

Charles R. Hill

iTrader: (7)

Those places are good places to buy parts but get it from BHR and you can bring the car by for free installation.

Dizzle

Hey guys,

I'm glad you were able to resolve, or at least pinpoint, the issue you were having with your battery Rob. I dont have so much of a problem but more of a concern with my battery. I live in GA and my "concern" started this summer, and its been pretty hot lately. I address this as a factor. My concern is when I drive over 70 to 80 mph or over on a highway my battery light will come on and stay on until I depress the clutch and let the engine rev down. Then light will then turn off immediately. When put it back into gear, the light will then turn on again after a few minutes of driving over 70 to 80 mph. This happens especially during the day when temperature is at its highest. If anyone has had any similar experience or if anyone knows what the potential problem could be please let me know. I dont want to find my self stranded on the side of the road one day...

Charles R. Hill

iTrader: (7)

That is likely to be an alternator problem but you can verify by using a real-time OBD scanner to monitor the alternator output at those engine speeds.

Ryan X-8

dude, that's the same exact issue my 8 started doing this week.
I replaced my battery & alternator with from o reillys and i still have the problem.

So it might be because the alternator isn't oem?

mmalson

I have exactly the same problem that Dizzle has.

I have also noticed another sound recently under my hood -- a whine (NOT a squeal) that tracks engine RPMs perfectly. Do alternators make noise when they fail? No noise is coming in over the radio. I sprayed belt dressing on, just in case -- no help. Could there be a tension problem?

heartygrain

Same exact problem as Dizzle and Mmalson here. Replaced battery last fall and the positive clamp to the battery and the problem went away for almost a year. Now it is back. It's done it on and off since 30K miles, I'm at 107K, so failure does not seem imminent. Would love to know why it comes on occasionally, usually around 3250-3500 rpms. Just like Dizzle if I put in the clutch it goes away. I may have to buy a scan gauge to monitor what's going on when the light comes on. When I check the alternator output at home it's right at 14.2V. Battery was just load tested and it's fine. Tricky one.

foxgoku

I have this exact same problem. I had the starter, battery, and alternator tested at Autozone last week and they all passed. I bought a new battery last week because my existing one was spitting acid. When I took it in, it tested good but had a temp of over 118F, which they said was very high. When I replaced the battery, the problem was on instantly at first, not just when the RPMs are above idle. The battery started to be dead a couple days ago, and would have to jump it. After the second day of this at work I decided to get it all tested again on the way home from work. When I went to have them tested, they couldn't because their machine was broken. I asked if they could jump me so I could get my new battery. They jumped me and I started on my way out of the parking lot. Then my wipers went on fast and the stopped and then fast then stop. Also my headlights would go on and off. I started to turn around to park it and I heard a pop behind the dash. Pulled in and parked overnight. Next day replaced the alternator, but now I don't get anything when I try to start it. The relay makes the sound but that is it. No crank over. Code scanner is now giving a readcode error. Key in car light flashes rapidly after trying to start the car. Power lock fuse blows immediately upon inserting new fuse. Took it to the stealership and hope I will have an arm and leg upon discovery of the problem. Battery had up to 18V while engine was revved, 13.8 at idle.

VOODOO8

Haunted 8 Ride - you might need to bring it to a priest for an exorcism instead

Seriously, with that many electrical issues going on I would hazard three guesses:
* Bad ground someplace within the electrical system. Would need to pull down electrcial schematics to trace and test (search and you'll find them, they are referenced in anumber of threads).
* Short in wiring or connectors. Same approach to diagnosis, just more tedious and time consuming.
* Computer issue. Either something is shorting out a computer board or the computer itself is toast.

Once you get those issues cleared up you might find this thread to be of help in diagnosing your single click starter issue: https://www.rx8club.com/series-i-trouble-shooting-95/car-wont-start-out-town-desparate-205809/

foxgoku

thanks for the info, I was looking at that earlier. I believe my problem is different because mine does not even make the first click when trying to start it. It is more like the key is not even programmed. After holding for 30 minutes, the stealership told me that the sunroof motor and the light autoleveling motor were both shorted and need replaced. They wanted me to pay for that to get fixed first before troubleshooting further. I mentioned to them that maybe they could just remove them from the circuit, i.e. remove the fuse, so that troubleshooting can continue. They said they would have to talk to their 'tech' to find out. I called again later for a check up, they said that after they did what I mentioned that the car does not seem to be communicating at all. They also said that the PCM smells burnt. They are going to try to reprogram it tomorrow and find out if that is the case. If the PCM is toast do you think that could have been what caused the other failures?

VOODOO8

Never happened to me personally so can't comment from fact, but it seems like a reasonable possibility.

Winning 8

I don't have the wiring diagram of the 8, but if it's similar to the 00 Miata then the alternator could fried your PCM because the alternator is wired to the PCM.

mmalson

FWIW, I'm having a discussion about one of the issues brought up in this thread on another thread. This thread is specifically about the alternator light coming on while cruising at 70-75 MPH at 3000-3500 RPMs with no CELs and no other symptoms:

https://www.rx8club.com/series-i-trouble-shooting-95/charging-light-comes-around-3500-rpms-207912/