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Discussion Starter · #1 ·
Sorry if this has been posted before - if it has, I can't find it.


I have an '05 MDX with about 150K miles. Was having starting issues and determined the alternator was dead after putting in a new battery. I replaced the alternator with a new one from Autozone and dropped in another new battery to ensure all was good. For a couple weeks while driving the electrical light (looks like a battery) kept coming on intermittently. I knew there had to be something going on as I know that means the battery isn't staying charged. I've been good at running it every day but just yesterday was the first day I didn't turn the ignition and of course today it now won't start. My connections are tight, I haven't checked any fuses yet and no, no interior or exterior lights have been left on to drain the battery. Do I have a bad (new) alternator / battery / or is there something else? Not sure what I'm missing. Any insight is much appreciated.


Thanks!
 

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You may have an undetected battery drain. Quite a few cases of Handsfree system causing battery drain.

good luck
 

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Yes, the handsfree system sometimes gets stuck on 'ON' and is 'listening' for commands.

It's located behind the garage door opener, you have to remove the whole top center console to get to it. Took me about 20 mins, but I have the pry tool kit that I bought from Harbor Freight to help speed that up.
 

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Same problem happening real time with my 02 MDX. Batt and Brake light were on intermittently at first but now constant. I tested my alt and it wasn't charging the batt at all. Today I dropped new alt, belt and batt in but still have brake and batt light. I'm convinced there is a short in the engine compartment/fuse panel since my symptoms started right after I replaced my power steering pump.

I am following the FSM troubleshooting and will share anything that helps ID the issue.
 

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Don't forget it didn't have to be draining, it could just not be charging and the driving is draining it. Test charging across battery when idling should be like 13.5 to 14v or something similar. Is belt good and tight. Check grounds on the vehicle, the can corrode and break off, too.

Sent from my XT1585 using Tapatalk
 

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Discussion Starter · #7 ·
Thanks for the added info. Where do I check the grounds on the vehicle?
I did disconnect the HFL - only took about 5 minutes. It'll be easy to replace or reconnect if I determine I need it again. I haven't had a chance to hook my multimeter yet so not sure if this has helped. I drove around yesterday and the warning lights never came on but they did when I took it out today. Seems to only come on when at a low idle, never at any speeds over 10-15mph
 

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FWIW the lack of quality of parts store "Rebuilt" alternators is famous in the industry. The "Rebuilders" take apart a bunch of returned units, and re-use anything that is not actually broken. Bearings and diodes usually get re-used, many times the regulator is replaced with a Chinese knock-off that almost never performs to spec. They can over charge and ruin a new battery. I can't count how many times I have seen owners and shops install 3 or 4 of these units before they get one that works. This info is based on my 45 years in the automotive parts and service industry.

Bottom line is do not assume that your "new" unit is any good. Do a full test of the system AND your alternator.

To start with, I suggest a voltmeter that plugs into the power socket, so you can monitor what is really going on. Manually charge the battery so that it is not going to overload the system. If you show voltage below 13.2 volts with the engine running, tap the alternator case firmly with the wooden handle of a hammer. If the voltage jumps around, you have a bad alternator without any doubt.

Good luck
 

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Discussion Starter · #9 ·
Thanks BluePill - I've been leaning towards this line of thinking already. I've been crazy busy and haven't really had a chance to look deeper into this, but when I do I will be sure to share an update.


Thanks


FWIW the lack of quality of parts store "Rebuilt" alternators is famous in the industry. The "Rebuilders" take apart a bunch of returned units, and re-use anything that is not actually broken. Bearings and diodes usually get re-used, many times the regulator is replaced with a Chinese knock-off that almost never performs to spec. They can over charge and ruin a new battery. I can't count how many times I have seen owners and shops install 3 or 4 of these units before they get one that works. This info is based on my 45 years in the automotive parts and service industry.

Bottom line is do not assume that your "new" unit is any good. Do a full test of the system AND your alternator.

To start with, I suggest a voltmeter that plugs into the power socket, so you can monitor what is really going on. Manually charge the battery so that it is not going to overload the system. If you show voltage below 13.2 volts with the engine running, tap the alternator case firmly with the wooden handle of a hammer. If the voltage jumps around, you have a bad alternator without any doubt.

Good luck
 
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