Taillights on 2007 Prius keep burning out, dealer says no problem

Measure the 12v bus actual voltage when your Prius is in "ready" mode. You can measure it at any 12v point in the car with a digital voltmeter or use the Multi-Functional Display (MFD) in maintenance mode. See:
Checking 12v Battery Health - Hybrid Car Forums
For detailed instructions.

If the battery voltage under charge is above 14v (most usually run at 13.8 volts), your charging system has a problem and is running too high for the bulbs and the little 12v battery.

JeffD

 

In addition to the above suggestion make sure you are using the correct bulbs, owner's manual should list the right ones. Clean the bulb sockets good and get any corrosion out.

Also make sure no water is leaking in, if water drips on the hot bulbs they sometimes crack and that causes them to burn out.

If you don't find the problem yourself there may be a shop that specializes in automotive electrics you could take it to, they might be interested enough to find out what is going on. I would steer clear of that dealer.

 

I watched the Voltage on my Prius for a while with my ScanGauge and it normally runs between 13.5 and 14.5, apparently depending on the state of charge of the 12V battery. I have owned a couple of older Hondas that run at 15V, this was by design and considered normal, apparently Honda liked higher voltages. They did seem to burn out headlight bulbs every two or three years but no other problems.

So I don't think you have a charging system problem from what you have seen so far. You might consider monitoring it while you drive for a few days and make sure it doesn't go way up every once and a while. I think it would take well over 15 Volts to burn out bulbs at the rate you experience. Also if it were the charging system I think you would be seeing other problems as well.

I would look for poor grounds and bad connections that could cause voltage transients. I know it sounds weird but I think bad connections can cause bulbs to fail prematurely.

 

So, how are things? I'll be changing my left rear bulb, tomorrow. Need to take care not to get body oils on the bulb, lest it leaves a hot spot.

 

In case you are interested, there are 5w LED bulbs that will give longer life.

 

Two weeks ago someone pointed out that my driver side tail light was out. I removed the bulb, located replacements on Amazon, but noticed equivalent LED lights and ordered a pair of those instead. Both bulbs were easy to replace (much easier than the headlamps!) and they looked even in brightness.

However on longer drives I began to notice a distinct electronic burning smell, and eventually decided to take a look at the LED lamps. Well, the driver side lamp was melted and toasted looking. The other lamp is fine. Clearly there is an electrical problem, and it is not even on both sides. Also - it generally takes a fairly high overvoltage to burn out electronics like that, not just a slightly higher voltage. I will check the battery health in maintenance mode.

FWIW - I did have a new main battery installed just a few months ago - the first major repair to my 2007.

Has anyone else experienced uneven tail light burn out?

Solutions or thoughts?

 

Rather than guess, I suggest that you will need a digital multimeter so you can measure voltage leading to the lamps on both sides. The problem could be a defective lamp assembly.

It is not obvious that uneven voltage is the problem, and further, it is highly unlikely that the voltage on one side would be much higher than the expected voltage of around 13.8V when the Prius is READY.