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Hi all.
I’ve been having this issue for some time now, the licence plate bulbs get REAL HOT and often blow.
The dealership replaced them like 2 months ago when both blew out, now one has already blown out and the other is running HOT on the point of melting the cover, never used to be like this only in the past year.
I’m thinking some wiring is corroded or something is shorting the connection.
None of the other bulbs at the back run this hot (tail light, break light).So what could be causing this issue ???
Thanks,
Crackerjack.
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Replies
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With a meter check the voltage to the bulbs. should be
12v see if its low or high. check that the correct bulbs
are in there. A larger bulb will burn brighter and hotter.
also check the sockets themselves for corrosion and heat spots/discoloration.Hmm, this is a puzzler, I see on the Internet that other folks have had bulbs blow out frequently on this car.
Prob is, the only way you can overstress a bulb is to apply excess voltage, and that’s real hard to do as the battery is a real firm stabilizer, even with a runaway alternator on full charge, the voltage won’t get much above 14.5 volts.
And that would overstress all the bulbs, not just the license plate ones.
And there is no way a loose connection or a short can give you MORE voltage, its always less.
So were mostly stumped. Some wild possibilities:
(1) You have a big bass speaker back there. That will vibrate the rear deck and stress the bulbs. The taillight bulbs are sturdier.
(1.5) You have a big amplifier back there, hooked up to light bus somehow (unlikely). The amplifier can push back some voltage into the 12 volt bus, if the wires from the fusebox are not sturdy enough.
(2) You’re putting in bulbs that are too powerful or too large in wattage.
(3) You’re buying the cheapest Chinese-made bulbs. They are about as strong as angel-hair.
(4) The bulb covers were designed to be too tight, keeping in lots of excess heat.
If you want to fix this, you could try putting in sturdier, perhaps USA-made or more expensive bulbs.
Or bulbs of lower watts or amps.
Another way would be to dim the bulbs a little bit by adding a resistor inline with the wire going to the lights. Go to radio shack and buy two 1 ohm, 2 to 5 watt resistors. One or both of those in series should dim the bulbs a little bit and increase their life by a lot.
🙂 When any electrical item, either a bulb or a wire or a fuse get hot, it is due to resistance. Resistance to current flow make heat, and in most cases it is due to a ground problem. Most bulb sockets have two wires, one for power and the other one for a ground to make a complete circuit. Some members are suggesting that too much current is the problem, it could be, but not on just one circuit. All your wires would have bulbs getting hot if the overall level of current was too high. I would look at your ground wire locations at the bulb. You will need to run a resistance check with a digital meter to see how much resistance you have. I would look at the wires of the license plate and follow them to the ground location. If this car is being driven up north where there is salt used on the road, I would look for wire being corroded, it would be rare for both license plate bulb sockets to short at the same location, but it could happen. Good Luck.
One winter I got out of a Ford I was driving and there was a noise coming from the front wheel well. It was a marker light. The streets were sloppy with snow and had been salted. The salty water was causing a short and enough current was flowing to cause the water to sizzle at the light. Rinsing and sealing things up was the fix.
Thanks all for your replies.
I’m honing to check out the bulbs today and take some photos of the reading from the multimeter if I get time.The wrong bulbs would be my guess. If the candle power of the bulbs is too high they will run too hot.
I mostly agree with the above suggestions. Basically it’s either a short within the fixture causing extra heat, partially bypassing the bulb; or the bulb you are using is consuming too many watts, overheating that little plastic compartment. I’m going to guess it’s the wrong bulb, since a short would more likely cause the light to burn dim, and you are describing a really hot bulb. As with any light bulb, there is a maximum wattage that any fixture can tolerate. High wattage bulbs make more light but have lower resistance, causing higher amperage to flow. If you use a higher wattage bulb than the fixture allows, you risk overheating and a fire. I don’t think it’s anything to do with the ground side of the circuit, since that would normally cause extra resistance in series, lowering the voltage drop across the bulb, not overheating.
Newer light circuits sometimes use a PWM circuit, and some of the newest use LED bulbs, which are a different game entirely. In that case the solution could be much more complex.Thanks to all that have replied.
I pulled the blown bulb out and tested the connection with my multimeter, reads at a constant 12v, checked resistance as well.So the bulb is burning too bright, I think the dealership put some dodger ones in, I live in china so it didn’t surprise me, everything here is profit first quality last.
I’ve found some 12v led bulbs online that I will get soon, I’ll get some pics of the bulb in question.Again, thanks for all the help.
The LED’s might be the fix. It seems awfully new to have an issue with too much resistance caused by corrosion but I could be wrong. I find the best way to observe a circuit is by doing voltage drop testing. More info in this article.
http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems
Keep us posted on your progress.
Just as a quick mental note, using LED lighting for any circuit that many modern vehicles monitor for load will ironically require use of a resistor (of the proper rating) to avoid odd behavior (cutting in and out, fast flashing, etc) and in many cases outright vehicle trouble-code(s).
I don’t believe this will be an issue for the license plate circuit though.
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