battery light
06-13-2012, 08:11 AM
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battery light
so it's either alternator or the battery from my search. i know optimas don't fare well with sitting around, so i first replaced my optima with another one. but the battery light is still on. i then checked the alternator with the voltmeter and when I idle the engine at 2000rpm, alternator lead does read 12volts.... in the meanwhile battery light is still on, and i can't really figure this out.
my alternator is brand new 200amp rx8 alternator from ebay. apparently they modified the stock alternator for 200amp's. i don't really care for it but interally regulated one i wanted use didn't clear the tps, so i just wanted to go back to stock.
my stock rx8 ECU is working and powered, and two wires from the alternator is hooked up to my ECU correctly (triple checked). could someone help? thanks all!
my alternator is brand new 200amp rx8 alternator from ebay. apparently they modified the stock alternator for 200amp's. i don't really care for it but interally regulated one i wanted use didn't clear the tps, so i just wanted to go back to stock.
my stock rx8 ECU is working and powered, and two wires from the alternator is hooked up to my ECU correctly (triple checked). could someone help? thanks all!
06-13-2012, 10:56 AM
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06-13-2012, 12:43 PM
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yea i measured it with voltmeter with battery charge cable off the alternator. so it was just alternator making 12v at 2000rpm. i'm just getting oem one from autozone this weekend.
06-13-2012, 12:43 PM
#7
Uncontrollable drifter
Stick, I'll let you in on a little secret. Find the wide square plug that connected to the MAF sensor on the original stock intake tube. Find yourself a MAF if you don't have one, then plug it in. It's something I figured out during my swap, without it it'll only charge about 11.8v. Trust me it works!!!
Now, if you don't have or can't find that plug, and don't have the sensor you go by another route. I believe you have a Haltech right? If so, disconnect the two wires and run a pwm or aux. out from the ecu to the alternator. There is a choice in there for Mazda alternator setup, Mazda's isn't simply a on/off charging system. You should go the stock route though.
Now, if you don't have or can't find that plug, and don't have the sensor you go by another route. I believe you have a Haltech right? If so, disconnect the two wires and run a pwm or aux. out from the ecu to the alternator. There is a choice in there for Mazda alternator setup, Mazda's isn't simply a on/off charging system. You should go the stock route though.
Last edited by dznutzuk; 06-14-2012 at 04:09 AM.
06-13-2012, 12:52 PM
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Stick, I'll let you in on a little secret. Find the wide square plug that connected to the MAF sensor on the original stock intake tube. Find yourself a MAF if you don't have one, then plug it in. It's something I figured out during my swap, without it it'll only charge about 11.8v. Trust me it works!!!
Now, if you don't have or can't find that plug, and don't have the sensor you go by another route. I believe you have a Haltech right? If so, disconnect the two wires and run a pwm or aux. out from the ecu to the alternator. There is a choice in there for Mazda alternator setup, Mazda's is simply a on/off charging system. You should go the stock route though.
Now, if you don't have or can't find that plug, and don't have the sensor you go by another route. I believe you have a Haltech right? If so, disconnect the two wires and run a pwm or aux. out from the ecu to the alternator. There is a choice in there for Mazda alternator setup, Mazda's is simply a on/off charging system. You should go the stock route though.
06-13-2012, 01:03 PM
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I had heard this for my Miata as well when discussing the Hydra ECU with Flyin Miata. They mentioned in the "what to do to return to stock" list, "reconnect Air Intake Temp sensor, because the ECU won't let the alternator charge the battery if it can't see the intake temp." When I inquired further about this oddity, they said that it has to do with trying to determine battery temps to prevent an over-charge, and ignores the fact that the battery is in the trunk, not the hot engine bay. (for the Miata).
I had a suspicion that Mazda continued this with other models as well, but nice to see it confirmed. MAF serves the same AIT purpose for the 8 I believe, I don't think we have an independent sensor there? My 99 Miata's is separate.
I had a suspicion that Mazda continued this with other models as well, but nice to see it confirmed. MAF serves the same AIT purpose for the 8 I believe, I don't think we have an independent sensor there? My 99 Miata's is separate.
06-13-2012, 01:50 PM
#13
Uncontrollable drifter
I figured it out by reconnecting everything on my car after the swap, and then slowly removing stuff and finding out what works and what's not needed anymore. That's how I found my traction control to work also.
06-13-2012, 03:33 PM
#14
thats true --i have been doing some stuff with the kenne bell boost a spark and have been measuring system voltage for a little while. The voltage/temperature compensation is definitly there.
I wasnt sure if it was going by ect or iat--so thanks for the clarification!
I wasnt sure if it was going by ect or iat--so thanks for the clarification!
07-24-2013, 05:23 PM
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Hello everybody, I am having a weird issue with my car. I have a 2005 AT RX8 and the problem is that when I start the car in the morning the alternator is not charging the battery, but if I wait 10 minutes the alternator start to work. While the car is running everything is ok, but If I turn off the car and I try to start it again after few hours, the problem appears again. I have a volt gauge in my car and that's why I am sure that everything works fine while I am driving.
12-31-2019, 09:30 AM
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Sorry, new here, recently purchased a 2007 RX8 for our son and has been a great little car. Recently the battery light came on and the next day it wouldn't start. I had alternator tested it failed, replaced battery and alternator. Now, battery light is still on and vehicle will not start still. Asking for some guidance, please!
12-31-2019, 10:08 AM
#18
Sorry, new here, recently purchased a 2007 RX8 for our son and has been a great little car. Recently the battery light came on and the next day it wouldn't start. I had alternator tested it failed, replaced battery and alternator. Now, battery light is still on and vehicle will not start still. Asking for some guidance, please!
Battery light will be on until it starts...
05-14-2020, 10:11 PM
#21
the prior responses are a little confusing because they aren’t explained.
im having an issue with the battery light being on. I’m showing generally around 14.2-14.4 charge/run voltage and around 12.2-12.4 voltage when off and running the stereo.
it runs great and seemingly charges ok, but I’m not sure what the threshold voltages are for the light.
ive moved the battery to the trunk and installed an aftermarket stereo, amps, and capacitor.
im having an issue with the battery light being on. I’m showing generally around 14.2-14.4 charge/run voltage and around 12.2-12.4 voltage when off and running the stereo.
it runs great and seemingly charges ok, but I’m not sure what the threshold voltages are for the light.
ive moved the battery to the trunk and installed an aftermarket stereo, amps, and capacitor.
05-15-2020, 02:33 PM
#22
the issue is that the original problem the thread is based on involved a heavily modified 3-rotor engine conversion and the problem was the new engine no longer used the factory MAF sensor. Which as noted, the OE system uses the MAF sensor as part of the alternator charging process. So not having the MAF sensor plugged in was the cause of that particular problem.
the reason it’s confusing to you is because you have a different alternator problem and are off topic in the wrong thread.
the reason it’s confusing to you is because you have a different alternator problem and are off topic in the wrong thread.
05-16-2020, 04:47 PM
#23
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I had heard this for my Miata as well when discussing the Hydra ECU with Flyin Miata. They mentioned in the "what to do to return to stock" list, "reconnect Air Intake Temp sensor, because the ECU won't let the alternator charge the battery if it can't see the intake temp." When I inquired further about this oddity, they said that it has to do with trying to determine battery temps to prevent an over-charge, and ignores the fact that the battery is in the trunk, not the hot engine bay. (for the Miata).
I had a suspicion that Mazda continued this with other models as well, but nice to see it confirmed. MAF serves the same AIT purpose for the 8 I believe, I don't think we have an independent sensor there? My 99 Miata's is separate.
I had a suspicion that Mazda continued this with other models as well, but nice to see it confirmed. MAF serves the same AIT purpose for the 8 I believe, I don't think we have an independent sensor there? My 99 Miata's is separate.
Once I ran my car, 05 plate with MAF unplugged for few miles and didn't get battery light. On one occasion I got battery light and it was
when I have lots of long starts after seafomed engine. later, surprisingly alternator was charging 14.4 volt and engine running with on battery light for 4 min.
Battery light is another dummy on instrument culture IMO, like water and oil.
ECU can feed ambient temperature from A/C sensor
I believe various markets have diff ECU-rom, hence diff behaviour!I never see ECU program for alternator charging, lots of M-BMW's have variable battery charging strategy like cutting out rotor charge on acceleration and getting
full power charge on car braking, which cause lots of thermal shock to alternator hence they use water cooled types.
06-06-2020, 09:33 AM
#24
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Random stall
So I had my 8 for about 2 weeks, only got to drive it twice, been down cause of fuel pump line backing off. So I take my car to the car wash after driving it all day to make sure the car is fine. Starts great cold and hot, don’t misfire but bogs a little towards 9k, po said need to change headers to catless (have been supplied). Well wash my car and my gf complains it’s hot. So start the car, warm not fully operating temp, and turn the ac on. I get out the car and it’s idling fine. Next thing you know, car just dies and I haven’t been able to start it. I do have an aem air filter that is expose. I didn’t know this and it got wet. Could that possibly be my issue? All help will be appreciated I just wanna drive my car instead of it sitting
06-06-2020, 04:46 PM
#25
nobody can answer your question. It could be anything, even a blown fuse.
You first have to determine if it’s getting fuel into the engine and the sparkplugs are firing. Because it takes both fuel and ignition to start and run. Then assess it from there. If you get it running again they sell a sock/sleeve that goes over the filter that lets air in but keeps fine dust and water out. If it already has the sock on it then that likely isn’t the problem.
If it got wet then taking it off and trying to start it is one way to tell if it being wet is the problem. You obviously don’t want to drive it like that, but just starting it up as a test is ok, but try to make sure nothing gets sucked up in the tube then; don’t go zinging the throttle etc. Just try to start it and idle. If that works then the filter will need to dry out. You should inspect it for obvious damage too. it probably means removing the front bumper cover to get to it though.
You first have to determine if it’s getting fuel into the engine and the sparkplugs are firing. Because it takes both fuel and ignition to start and run. Then assess it from there. If you get it running again they sell a sock/sleeve that goes over the filter that lets air in but keeps fine dust and water out. If it already has the sock on it then that likely isn’t the problem.
If it got wet then taking it off and trying to start it is one way to tell if it being wet is the problem. You obviously don’t want to drive it like that, but just starting it up as a test is ok, but try to make sure nothing gets sucked up in the tube then; don’t go zinging the throttle etc. Just try to start it and idle. If that works then the filter will need to dry out. You should inspect it for obvious damage too. it probably means removing the front bumper cover to get to it though.
