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Discussion Starter · #1 ·
Hi all, this is a strange one!
My car drives normal for a while and then all of the sudden the radio acts strange, cutting out, sound like static. This is the first indication that there is a power problem.
Next the car downshifts roughly and hard then back up again right away and the red battery light comes on.
at this point the electrivcal is shorted because I measure the battery voltage at 6.0V!!!???
the car still runs. Then I lose my instuments and lights, wipers, door locks, everything except for the power steering and the engine is running! (barely)
I drove it like this long enough to shoot avideo of it and then limped it to a parking spot before it finally died. I shut the ignitio off and measured the battery voltage again at 7 v. this indicates a short somehow (I'm assuming alternator) because this happened a few times and nothing burned or melted. After recharging the battery the car starts up like normal but then while driving around the block it did it again.
I can assure you that I lost all electrical in the car except the engine was still running. I read another reader's question and no one believed the car was running but this car is RUNNING with no electrial elsewhere in the car, not even LED dome lights.

Any help would be appreciated.

Also the car engine was labouring and running rough as if possible fighting masssive counter EMF from the alternator or something...

Thank you all in advance!

Jay
 

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Don't drink and drive
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Alternator most likely.
 

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Discussion Starter · #3 ·
Thank you for your thought. I suspect it too but i loathe dealership practices and "diagnostic service/charges"...
 

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Don't drink and drive
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Find a local shop, maybe find more, and call and ask how much an alternator replacement would be. Avoid the dealer. You can also buy your own and ask how much it would cost to put it on.

Your battery voltage should be around 13.5-14 or so while the car is running. The fact that you're getting 6 is telling me that your alternator is gone.
 

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Discussion Starter · #5 ·
Agreed. It starts and was charging at 13.9-14V so I closed the hood and went around the block. Then it got wierd again and I ripped open the hood to measure 6.0v which the car shouldn't be able to run on i wouldnt think but it did (sort of). To see 6v and have it completely kill the battery in seconds to me hsould either burn or melt something or be related to the alternator somehow is what I think but want to confirm with you online experts since I'm an electrician/millwright by trade, not an auto mechanic. Plus us drive Hondas so rarely have to work on them... :p

Thanks again. I appreciate your input.
 

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Elvira
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The alternator diodes are bad.

The static you hear is AC leaking into the system. Bad diodes will do this.

Measure the AC volts at the battery posts. If greater than 50 millivolts of AC, the ripple is too high and there's a problem with the diodes.

If not all the diodes are bad it may LOOK like the alternator is working,(electrics in car work) but no battery charging is occurring.

WAG though is the diodes don't act up until they get hot and that's why the car will start OK after charging but then cause problems during the drive.

EDIT: It's best to measure ACV at the BAT post on the alternator but at the battery posts will direct you to the alternator.
 

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I think your alternator is bad, but first check all the basics.

1. Both connections to the battery need to be clean and tight. If you can wiggle the connections at the battery they are not tight enough.
2. Verify the body ground is clean and free from rust.
3. Verify that all engine and transmission grounds are in place and clean and tight as well.
4. Verify the belt driving the alternator is not slipping, the belt is in good shape and not stretched and the tensioner is working properly.
5. Verify the battery is in good shape and have it tested to make sure it is working properly.


I suspect your alternator is bad, but a reading of 6v at the battery after a few minutes leads me to believe the battery may have an issue as well. In general the car will stop running at a voltage below about 11.5v.

Sent from my Nexus 5X using Tapatalk
 

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Elvira
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I think your alternator is bad, but first check all the basics.

1. Both connections to the battery need to be clean and tight. If you can wiggle the connections at the battery they are not tight enough.
2. Verify the body ground is clean and free from rust.
3. Verify that all engine and transmission grounds are in place and clean and tight as well.
4. Verify the belt driving the alternator is not slipping, the belt is in good shape and not stretched and the tensioner is working properly.
5. Verify the battery is in good shape and have it tested to make sure it is working properly.


I suspect your alternator is bad, but a reading of 6v at the battery after a few minutes leads me to believe the battery may have an issue as well. In general the car will stop running at a voltage below about 11.5v.

Sent from my Nexus 5X using Tapatalk
Yes @greg1c is correct to point out checking all that first. My bad to jump to a conclusion.

The 6v might be the diode shorting out allowing the stator to put a load on the battery bringing it to 6 volts. Not arguing the 11.5 volts or less but ALTHOUGH NO ONE SHOULD DO THIS the car will run with the battery disconnected aside from the voltage dump that occurs when that happens. Even at 6 volts wouldn't that still allow the battery to act as the "filter" ? or does the battery charge system automatically kill the juice and shut the engine down?
 

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When I heard the symptoms I thought the alternator was going over voltage. It could be over voltage with A/C, instead of DC. A high resistance connection at the battery could be creating issues as well. Check the basics and get the battery checked. If you are mechanically​ inclined pull the alternator and get it checked off the car.

Sent from my Nexus 5X using Tapatalk
 
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Elvira
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@Jay Lee

Well, what happened? What did you find ?
 
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