Another cause intermittent or permanent headlight failure can be found on the post by SEVARGMT on 9-29-2010.

It seems to lie in corrosion of the wiring system connectors in the PJB, a specific wire connection junction box located under the passenger side glove compartment box.

It seems possible to repair the corroded pin connector but it is probably best to have the dealer replace the entire PJB to avoid repeats of this problem, as it is a dangerous situation when headlights go out at night, like mine did.

Brilliant problem solving by SEVARGMT and DJS2571. They also developed a convincing theory of what causes this problem: the air conditioning line located above this box creates condensation, which then drips down on the wire connectors and causes them to corrode, causing an electrical fault. They suggest a plastic drip sheet to avoid future corrosion.

Wouldn't it be great if Mazda assigned an engineer to read the forums for problems with their cars and prepare posts with solutions? It is plainly obvious that a problem is very common when you look at the number of "views" listed for certain topics, such the headlights (many thousands of owners have headlight failure problems). Mazda should have issued a bulletin or a recall since the corroding PJB is clearly a safety problem. This looks like a design/engineering flaw. Every electrician and plumber knows to never put moisture sources above electrical boxes. Shame on them.

 

skidder, no offense but I don't think it's an a/c line causing the problem. If I understand correctly, you said it was dripping onto an electrical box under the glove compartment. If that were the case, wouldn't there be moisture inside the car and a mildew problem would occur? That would be noticed very early on and give the owner time to have it fixed under warranty.

All the a/c condensation created drips out from under the engine compartment.

Again, I don't mean to offend you and if I misunderstood what you wrote please put me straight.

 

I am reciting a theory created by others, so i am not locked into it as a final explanation. I would think a small condensation drip falling directly onto a specific connector would not be enough for mold, but when combined with electrical charge could cause quick corrosion. One post said a mechanic or dealer added some clear gel to waterproof the connection. BTW, the PJB also has the fuse panel for many electrical components and has relays within it. The owners manual describes how to open it up to check fuses.

My 2004 Mazda3iT has had a number of low beam bulb failures over the years. Bulb replacements were required, but an arcing connector would put a great deal of intermittent electrical stress on the bulbs, shortening their life dramatically.

My advice would be to inspect the connector condition at the same time as checking the headlight fuses in the PJB before changing a bulb. Remove the connector by tilting the lever handle located on the center on the plug.

 

Mazda 6 headlight issue - common fault is ground cable from bulb holder, (ground is completed when spring clip is shut holding bulb). The ground connection that is attached to bulb holder dies, (ground is via Small black cable soldered to tab on the edge of the metal bulb holder).