Rear brake lights are of different bulbs

Tiny
STILLBILL2
  • MEMBER
  • 2002 DODGE CARAVAN
  • 3.6L
  • V6
  • 2WD
  • AUTOMATIC
  • 167,000 MILES
I have never seen this before. On my van listed above my left brake light was out. I went to replace it and it was so the type that you out push it down and turn. Old school. I looked at the right brake light n this bulb was totally different the more modern bulb just push down n that's it. What kind of setup would have two totally different bulbs as such? And no matter how many times I replace the push down and turn bulb it continues to burn out immediately.
Saturday, February 13th, 2021 AT 1:41 AM

8 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
Someone must have replaced the socket with the wrong style. You're describing the older 1157 bulb with the round, brass base. Even my '88 Grand Caravan already had the newer 3157 with the flat plastic base.

There's something else you're overlooking. A bulb can't burn out right away unless the system voltage is much too high, but then all the other bulbs would do the same thing. What you need to do is look closely at the bulb to see how it failed. If the filament is indeed burned out, my guess would be you're installing used bulbs. While this is a stretch because I've used old bulbs all my life in my vehicles, I've only run into this with sealed-beam head light bulbs that I saved from scrapped cars. It seems they must suffer the same fate as tv picture tubes that sit for a long time without being used. I suspect air seeps in. That will cause the bulb's filament to burn through in short order.

If you're simply running into multiple bulbs that stop working, a better suspect is corroded contacts in the socket, or wires that are corroding apart. A more elusive problem is when one of the contacts had a little corrosion, and that caused heat to build up when current flowed through it. That can cause a contact in the socket to melt into the plastic disc it sits in. Spring pressure will cause that contact to drop down, and it may only work when you push down on the bulb. A clue to this is to look at the two contacts on the bulb. Those are solder, and if those contacts got hot enough to melt the plastic disc in the socket, they got hot enough to melt away the nice rounded center of the bulb's contact(s).

Besides excessive voltage, excessive vibration will lead to early bulb failure. If a replacement socket doesn't fit snugly in the housing, it can bounce around. That will shake the filament until it cracks. You have to look very closely to see that crack. It usually shows up when you tap the bulb. That type of failure is quite different from one that burned out from age or excessive voltage. Those will have a tiny ball of metal on each end where the filament broke, the gap will be much bigger and easier to see, and there may be black areas on the filament or on the glass.

If you see white powder inside the glass, that is due to the entry of air. During manufacture, they put a powder in there, then explode it to burn off any residual air. That leaves a mirror or shiny-looking spot somewhere out of normal sight. That residue is what turns into that white powder if air gets in.
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Saturday, February 27th, 2021 AT 1:58 PM
Tiny
STILLBILL2
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  • 5 POSTS
Okay, thank you.
I bought the bulbs new one went out immediately with white dust in side the bulb. The next one went out as you can see the filament broke and hanging. I noticed nothing obvious regarding the round contacts. Im tempted to solder 2 wires on the next bulb and attach them to the right working brake light as those little 2x2's are getting a little pricey. I have a 1987 Dodge b150 and the left headlight went out then the replacement and one after. At what $11.00 each I took three wires and attached the next new headlight to the working one. I know now the correct fix but it's still working. Thank you
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Saturday, February 27th, 2021 AT 1:58 PM
Tiny
CARADIODOC
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The new bulb with the white powder was broken, possibly before you installed it.

For those expensive bulbs, I harvest them from salvage yards. If you go to one of the pick-your-own-parts yards, they'll charge you a couple of bucks for a coffee can full of bulbs and fuses. That's something people don't usually go there for, so they don't sell many. They feel a few dollars is better than pricing themselves out of a sale and ending up with nothing.
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Saturday, February 27th, 2021 AT 1:58 PM
Tiny
STILLBILL2
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Thank you.
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Saturday, February 27th, 2021 AT 1:58 PM
Tiny
STILLBILL2
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Okay, I have figured out what my issue was. Apparently the base of the bulb socket with the 2 solder contacts for the twist and lock in bulb. Somehow turned opposite of the bulb. When I twisted it for the bulb to lock in on the other contact it works like a charm. Go fish.
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Saturday, February 27th, 2021 AT 1:58 PM
Tiny
CARADIODOC
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So are you saying the two wires were switched or you were able to stick the bulb in turned 180 degrees? Of the two tiny lock pins that stick out the side of the base, they're at identical height on the single-contact 1156 bulb, but one is higher on the 1157. That's so they can't be installed wrong, but that hasn't stopped me from doing just that on more than one occasion. The socket has to deform a little, then that lets the bulb go in wrong and lock in place by just one of the pins.
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Saturday, February 27th, 2021 AT 1:58 PM
Tiny
STILLBILL2
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The wires weren't switched. The round base inside socket turned somehow where as the bulb contacts were lined up with opposite contacts of base. I turned it n the 1157 bulb locked in apparently on the rt contacts after turning it.
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Saturday, February 27th, 2021 AT 1:58 PM
Tiny
CARADIODOC
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Dandy. Happy to hear you solved it. Please come back to see us again.
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Saturday, February 27th, 2021 AT 1:58 PM

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