Cadillac Turn Signal Bulbs

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turn signal fog lamp assembly

This article will provide in-depth details about how to replace Cadillac turn signal bulbs that look like the one pictured on the right side. This bulb has two filaments and it also lights up for the daytime running light function as well as the turn signal and hazard flashers.

This also covers the high intensity fog lamp located in the same compartment. The specific pictures and instructions to follow cover any first generation Cadillac SRX from 2004-2009. But I do believe that the CTS from 2003 to 2007 have the same exact set up.

The reason I decided to post a how-to article is because replacing this bulb is a lot harder than you would expect. It took me a couple hours of poking and prodding before I accepted the fact it required pulling stuff apart to reach it. I will dig into details of exactly why below. I provide pictures of what’s necessary to get access to the Fog lamp, daytime running lamp and turn signal sockets.

bulb part numbersLet me give you some part numbers for the replacement bulb, because I had a hard time finding these. They weren’t marked clearly in English on the factory installed bulbs made in China. You can get the parts on this page or go to almost any big retail outlet and you’ll find the same bulb. The Sylvania number is 3757A. This is the brand most stores carry.

The A stands for Amber in color and note that some of the older cars are clear bulbs with an amber lens cover. Of course you can get these from any GM dealership. The GM part number is 15862271 and ACD# 23757NAK. The fog lamp bulb is a 9006b in my car but verify this on your specific model. Real quick though I wanted to mention what alerted me that a problem had developed.

How Can You Tell the Bulb is Bad

automotive troubleshooter voltmeterI went to make a right-hand turn and put on my turn signal. The light was flashing at a normal speed and then started to flash faster and faster. From my experience I know that the most common cause of this condition is a blown turn signal bulb. This is because the voltage and amperage running through the circuit has changed because it is no longer illuminating one lamp.

But to answer the question how can you tell that the bulb is bad what you really need to do is pull out the lamp and test for power and ground at the light socket. You can do this with a voltmeter or a test light. I went to perform this simple test and realized this was not going to be the simple operation I was hoping for.

Vehicle manufacturers often provide shortcuts to gain access to lamps that will require replacement several times during the vehicle’s life. In many cases a car will go to the junkyard with its original bulbs in place. But when it comes to daytime running lights these are illuminated more often than other bulbs on the automobile. For this reason they are one of the more common to fail. But GM did not provide a shortcut on this line of Cadillac cars.

How do You Get to the Turn Signal Bulb

fog light bezelI’m an experienced mechanic and have worked on General Motors cars for about 25 years. I wanted to pull the bulb out so I could test for power at the socket and if the lamp was bad I wanted to get the number off it so I could get a replacement. I took loose the bottom panel and stick my hand up inside. I could not feel a releasable socket. I then popped the hood and stuff my arm down and from the top side and again I couldn’t feel the socket.

Then I took loose the inner fender well cover and pulled it back and shine my flashlight in there and this is what I saw picture on the right. There is a bezel that covers the light sockets for the fog lamp and the turn signal bulb that also has a filament in it for daytime running lights. The shape of the bezel and the six retaining screws that are torx head made it necessary to remove this bezel by going directly at it. Meaning you can’t get it off from reaching them from the bottom or reaching in from the top.

wheel well removedI took the wheel off so that it would be easier to remove the wheel well but this is not a necessary step to get the wheel well out. I do recommending removing the wheel well because just pulling it back makes it harder to remove the six towards screws. After I got it apart I was able to access the Cadillac turn signal socket and test for power. When I pulled out the bold I could see that the filament inside was broken and lying inside. I went online to find out what the part number of the bulb was and it was not easier finding an answer so let me post it right here.

The Cadillac turn signal bulb is an amber 3757. This is a standard bulb that you should be able to get at a local parts store. My parts store was out of stock so I went to the dealership. At the dealer this single bulb was more than eight dollars where as in the aftermarket parts store a two pack was $5.96. Since I paid more I decided to make good use of my visit to the dealership and get a price parts and labor for how much this operation would cost if the dealer performed it. Replacing the turn signal bulb on a Cadillac SRX would have cost me $148 plus tax.

I have some related links to share. First is a cell phone video I shot and put up on YouTube because I couldn’t believe how hard they make it to replace daytime running lamps on a Cadillac. Second is a forum discussion over at repair pal about how common this is and several examples of repeat failures of blown turn signal bulbs on Cadillac models. Hint: If you get oily finger prints on the bulb it reduces the life of the bulb (my opinion).

So even though this operation is a pain and neck and you might have to buy a T-15 screwdriver you could save about $135 if you can figure out how to do it yourself. Hopefully the pictures and information I provided will go a long way in helping you to achieve that savings. Next link takes you to the homepage for more information and auto repair articles.

10 Replies to “Cadillac Turn Signal Bulbs”

  1. Jake

    This is much more complicated than changing a bulb on my car. On mine you can just pop the hood and take out the headlight housing.

    This is a very helpful guide for anyone who owns a Cadillac.

  2. Parrisk

    It takes about 10-15 minutes to drop the front bumper off the car.
    This is also the recommended way to change any bulb on the front of the car. After a few tries one can change a bulb in about 30 minutes. Of course it is a really poor design decision, specially if the weather is bad like in Winter when most cars it takes 5 minutes and no tools to change bulbs.

  3. Joe Lluve

    Cadillac SRX. This car seems to be designed, to be worked on by the dealer only. In order to swap out a simple turn signal bulb, you have to either drop the bumper or take off the wheel and inside wheel well cover. A lot of work, when it normally takes a few minutes in most cars. Is it a bad design, or motivated by greed? Thanks for the explanation above.

  4. lyn kroll

    Thanks mark for your efforts. you saved me 2hrs. what’s your idea on reverse lights on this ’04 srx? bulbs ck out ok and power is there but no workie.

    • Mark Gittelman

      Lyn: If the bulbs are good and you have power on the hot side when the gear selector is in reverse, then it has to be a ground issue. In the old days they were case grounded, but nowadays the ground wire can travel a long way to reach its destination. You might need a wire diagram to find the ground junction location. I have a Youtube video that explains how to test for a good ground.

  5. J. B Mace

    Try this first for any of the front lights. Hit the outside lens with the palm of your hand. My turn signals came on after much frustration from not knowing what to do. I took a lot apart and never got the headlight out. Good luck. Hope this works for you. No more Cadillac’s for me.

  6. Mac

    last time I looked up the bulb (sylvania) it came up as a 4157A. 4157 is a 7 watt version of the other ones mentioned here. Regardless, it lasts about a week as well. In my SRX the filament isn’t the problem, the wire carrying current to the filament is too small, it gets too hot, and melts the plastic underneath it. Then it loses contact with the socket. Next time you change one take a look. Looks like this: http://ww2.justanswer.com/uploads/dt69nova/2012-08-08_212232_pic.gif (BTW I’m not buying the replacement socket required answer) Next fix if I can’t make LED’s work I may slip a copper sliver under the wire to distribute the heat and keep the plastic from melting out from underneath the wire. Note that I haven’t tried this and if you do it, you do it at your own risk.

  7. Sharon

    My husband is a mechanic of 30 years and he said the blinker bulbs on my 2009 SRX were the most difficult he has ever done, and he works on all engines from lawn mowers to cars, trucks, RV’s, 18 wheeler, cranes, tanks, generators the size of a house, and much more. So for him to say that it must be hard. He also said the fuel filter replacement was ridiculous. He is now out of the Country and my blinker bulb went out so I had to take my car to the dealership to have them changed.

  8. Terry

    I took mine into the shop to have the alternator changed and when I got it back both front turn signals were out know anything that would cause this?

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