2009 with 160,000 miles... Several weeks ago, someone ignored my protests and plugged an inappropriately high-drawing inverter and a power-hungry laptop into my poor Fit. The inverter squealed in protest for a while, then killed the power outlet. No fuses were blown and everything else functioned. A cheap aftermarket replacement cobbled together with parts from the original (to retain the cap) was installed and all seemed okay until the battery started dying overnight. Jumping it in the mornings, it would restart fine throughout the day. I brought the battery to AutoZone for testing and was told it was bad, brought it to Advance Discount for its warranty coverage and was told it and my alternator were both fine, and repeated these actions a few times until O'Reilly's said I had a bad voltage regulator and that the battery was nearly dry. Advance Discount gave me a new battery and I have a new Mitsubishi alternator arriving tomorrow. I have a new Honda accessory plug to install as well.

I'm concerned though as to WHY my voltage regulator failed and whether my new parts will soon also be fried. I brought the old alternator to a local automotive electric shop and they confirmed that it is bad, but would not elaborate and acted like my concern that there is a wiring issue is some sort of paranoia. What can I do to check before I put my new parts in?

Apologies if this topic has been covered to death already. I don't have much luck with the search function on here. Thanks in advance for any info anyone can share!

 

Not sure.

The tiny alternator and tiny battery in the Fit provide very little power. I would have expected some fuse protection to kick in Honda can't engineer for all scenarios. I could see a modern high current, high speed switching supply your "colleague" used might have caused damage quickly.

The alternator's voltage regulator is a popular failure mode. If that goes bad, it can kill the battery. Not sure we can know what the cause was.

You should inspect the wiring system carefully as a large current burst could have melted some connectors or wires, which is not uncommon in cars. Start from the power outlet and check and work back to the battery, checking all the grounds and positive connections. I would also check the main wiring from the battery to the alternator and fuse panels.

You can start with a multi-meter checking continuity. Also visually check as much as you can. A voltage drop test is best and is easy to do; it shows if there is high resistance between two points. This should take an hour.

I think there are wiring diagrams posted here. There are some good videos on youtube for voltage drop testing and looking for wiring issues.

 

Thanks, this sounds like a good plan. I will give the drop testing a try.

 

Let me know if there's a specific area you need a diagram of, I have the entire service manual handy to thumb through.

 

Do you have the Electrical Troubleshooting Manual by chance? Is it worth taking a look at?

 

No further electrical issues, I'm happy to report! The cobbled-together plug had a short and was sucking the battery charge overnight, and I believe the voltage regulator was destroyed by having to jump the car quickly so many times.

 

Congratulations in resolving your electrical issue. I'm surprised though that the dash power outlet didn't blow a fuse before overheating the outlet. I think I would pull that power outlet panel loose again and just disconnect the factory supply wire to it, and cap off the loose wire. You can then run a new power wire from the under dash fuse panel a couple feet away. You can simply add the circuit by adding an "add a circuit" coupler which you can find on Ebay. This coupler adds the new circuit by clipping onto an existing circuit in the fuse box. The coupler includes a separate fuse for the added circuit and doesn't affect the factory existing fused circuit. You would probably then want to run a 10 amp fuse for the new power outlet wire.

To be thorough you should also label the new wire in the fuse box and if you have an owner's manual also make a notation there in the pages covering the fuse panel so any problems encountered with the circuit later can be easily identified.

 

You already have it solved, but in the future an easy way to check for what they call parasitic draw is to disconnect your battery negative terminal with the key off and and put an ammeter in line between the ground cable and the battery terminal. If you're drawing any significant amount of amperage (more than .030) you have a short somewhere, or something's not turned off.