C5 Stock Under Hood Lightbulb LED Conversion Tip
Thread Starter
5th Gear
Joined: Sep 2017
Posts: 5
Likes: 1
From: Seattle Washington
C5 Stock Under Hood Lightbulb LED Conversion Tip
Parts and supplies for resistor installation of under hood LED light bulb.
Completed LED under hood light assembly.
C5 Stock Under Hood Lightbulb LED Conversion Tip
The Circuit I am writing this Tip for is the one that includes the glove box light, the two Non-Dimmable rearview mirror lights, and the under hood light.
Stock GM Bulb Part Numbers are:
Mirror bulbs (2 each) PN: #212-2 10w@13v = 17 ohms (each)
Glovebox bulb (1 each) PN: #194 3.5w@13v = 48 ohms
Under Hood Bulb (1 each) PN: #561 12.5w@13v = 13.5 ohms
LEDs have a much lower resistance than stock bulbs. The Corvette onboard computer enables certain functions in circuits based on resistance. Without a minimum amount of resistance in many circuits, the computer will not operate functions properly. If every light in the circuit I am writing about has been converted to LED bulbs, there will be an irregular computer function, in addition, the computer will not time-out power in the circuit completely (15 minutes). What will occur, a lower current will continue to flow into the circuit indefinitely until the battery is completely drained. I measured between 6-7v, it is also possible to see a faint glow from any number of LED replacement bulbs in the circuit depending on the type of LED replacement bulbs installed. To correct this, I suggest to install a very rugged type heat sink ceramic resistor to the under hood replacement LED bulb (see image). The resistor type and value I selected is in part due to availability for purchase, never gets more than slightly warm regardless of any period of use, plus it hides away nicely under the hood lens to the rear of the bulb. The ohm value of the resistor I selected is a bit higher than minimum for assurance. I have included an image of everything needed to modify a replacement LED under hood bulb, and an image of the completed bulb modification assembly. I suggest NOT to bend any under hood terminals to fit the replacement bulb, or splice wires as a general rule. Instead, when mounting the modified LED under hood bulb into the STOCK bulb assembly, properly clean the copper contact terminals and solder the bulb in place, this is a much better option, especially in consideration that it is a high vibration area. There is no need to shrink wrap the resistor tails, they are flexible and ridged and will not come into contact with any other power source in this location. With the life expectancy of LEDs, you will most likely never have to remove and replace this bulb, if you do, easily heat the solder and remove, back to original configuration, without deformed terminals or wire splices.
I hope this information is useful, I am new to the forum and wanted to contribute something positive.
Last edited by Kittyboy; Oct 1, 2017 at 09:25 AM.
Thread Starter
5th Gear
Joined: Sep 2017
Posts: 5
Likes: 1
From: Seattle Washington
10/3/17 Addition:
Between the remote and non-remote type lighting control circuits, the remote has a resistor and diode in parallel as part to the instrument illumination. It is unknown to me the resistance value, so not quite sure how this difference may affect the TIP I posted with regard to proper computer operation, auto time out function?
Adding a bright LED type light under the hood, in my opinion, is an improvement over the stock bulb in total darkness. It is useful for locating battery terminals and other top surface components in a road side situation for a quick survey, but not really very useful for anything else, I suggest to continue and keep a good LED hand held light in your emergency kit. The under hood LED does help to conveniently showoff your engine in any case.
Between the remote and non-remote type lighting control circuits, the remote has a resistor and diode in parallel as part to the instrument illumination. It is unknown to me the resistance value, so not quite sure how this difference may affect the TIP I posted with regard to proper computer operation, auto time out function?
Adding a bright LED type light under the hood, in my opinion, is an improvement over the stock bulb in total darkness. It is useful for locating battery terminals and other top surface components in a road side situation for a quick survey, but not really very useful for anything else, I suggest to continue and keep a good LED hand held light in your emergency kit. The under hood LED does help to conveniently showoff your engine in any case.
Last edited by Kittyboy; Oct 3, 2017 at 03:35 PM.
