I'm having a series of what I will call electrical problems with my Mazda 3. I'm not sure if they are interrelated and wanted to get some advice or ideas from you guys. Apologies in advance for the novel..

First and foremost, the reception on my radio has degraded. First, it was a little static on the AM channels but recently it is both AM and FM and the static / interference has jumped significantly, even on local channels that should be crystal clear.

Second, my battery died. It was WELL over 4 years old and probably in need of replacement, but the next two items happened after replacement and I'm curious if there is a relationship:

Third, the cigarette lighter port on in my center console that I use to plug in an iPhone charger has stopped working. I checked the charger itself on another port and it still works fine. I had always had the problem of that port picking up engine noise, meaning if I was charging my iPhone with it and also playing music out of the iPhone, I would hear engine noise as well as the music. This was a manageable problem, but now the port just doesn't work at all.

Fourth, and finally, I have managed to lose both of my keyless entry clickers so I use my key to get in the car at all times. On several occasions now (and more so lately) I have run into situations where I unlock the drivers door, open the door, unlock all the doors and then, when another door is opened (or even the trunk) the car alarm goes off, even though all the doors were unlocked. I have to run over to the drivers side door and re-unlock the door with my key.

Again, none of these issues are that big of a deal but I am concerned that they are all somehow related. I'm also concerned that I will take the car to a mechanic or dealership without getting some advice on possible issues first.

I REALLY appreciate any help in advance that you guys as the experts can offer me

Thanks so much! Michael

2 Answers 2


By far the most common electrical problem, especially in cases like this where "mysterious" things happen, is a bad ground. They're usually very hard to find but very easy to fix once found. Basically you want to use a multimeter to measure the connection between the negative battery terminal and different places on your car that should be grounded, like the frame, or the cigarette lighter, or whatever. The setting where it beeps if the two probes are connected is the best for this, you don't even have to look at the display. Once you find a bad connection you trace it back to the battery, measuring along the way, until you get a good connection again, and at that point you know if it's a bad wire, rusted connection, loose screw, etc. It's often hard to understand exactly how a bad ground generates all the problems it does, but the cig lighter is straightforward and also the noise in the radio could be from the battery not connecting properly to the system (the battery acts as a large capacitor and smooths out electrical noise from the engine, so if the connection to it is not very good, it will do a bad job at that).

The second thing I can think of is that your alternator is busted. In particular if one of the diodes in it is toast, the alternator will still put out current, but it will be less than usual (would account for dead battery, cig lighter port not working) and also lots of spurious electrical noise. This is easier to check but harder to fix. Again, the test involves a multimeter. There are detailed instructions online, but the main points are that you want to be getting around 14V DC and 0V AC on your battery with your car running. Good luck!

  • @visd thank you so much for the comprehensive and informative answer. This is exactly what I was looking for.
    – Michael
    Commented Mar 10, 2014 at 13:41

I was having strange issues with my Mazda 3 as well, I checked the voltage to the starter and found that the main power lug on the starter was corroded so I attempted to remove it and the entire lug broke off. So in the process of removing the starter I found that there is a bracket attached to the starter mounting studs that has a battery ground cable on it, this bracket was loose so I am sure this was part of my issues. I will be replacing the starter and the bracket since the bracket was also corroded badly (road salt) but once they have been replaced I am hoping the issues go away.

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