Wavehogger

So I figured I'd check to see if anyone has replaced the door courtesy lights and trunk festoon to LED? I first replaced the door courtesy's last week and they worked fine. Then I put in a LED in the trunk to replace the festoon today and the interior 7.5a fuse blew right away. I checked the festoon LED in another car it works fine so it's probably something to do with the resistance in the circuit. I'm guessing it's because the rest of the interior lighting is all LED and maybe taking out the small resistance that the festoon provided in the trunk bulb is now causing it to short out? Anyone tried this yet or am I the guinea pig?

bmode

Well, I pulled out the housing on the driver door bottom courtesy light, and now it doesn't fire back up? Of course I was too lazy to take the other bulb out from the other side, but I'm am curious about why yours shorted out? You are the guinea pig, but the feedback is really appreciated Hogger.

Wavehogger

lol, bmode, wasn't it you who said to me on another thread that your door courtesy went out by itself and you were just going to have the dealer replace it? Or did you make it go out by pulling down the housing..and was that before or after the dealer fixing it I'm all confused..

And regarding the LED's.. Isn't it crazy that these cars are so specifically wired/engineered with certain resistances that you can't even change a festoon to an LED without blowing a fuse!

bmode

It is crazy. I don't know what I posted, lol, I might of mispoke? Dayum, getting old. Regardless if I touched it or not, why would it go out? I didn't pull on the housing, more so it just drops down and dangles. The little conductors are touching on the bulbs and looks just fine, I made sure of that? This whole circuitry has got me thinking now? In my 05 TL, it was a snap and everything worked?

Wavehogger

lol, I appreciate the honesty.. Sounds like the bulb either just happened to go out or it's not seated in the socket all the way. Did you take the plastic cover off that allows you access to the bulb? It's such a small filament it's hard to see if it's a good or bad bulb, but just have your dealer replace it. I would complain that a brand new vehicle shouldn't need a bulb. I doubt they'll fight you over 50 cents, but with sales down so much...

Bearcat94

I'm no electrical wiz, but I don't think it works like that. A fuse blows when you have too much current through the circuit. If it was the LED's you'd thnk guys who have replaced stock bulbs with LED would blow fuses all the time.



Here is my guess:

When you installed your Festoon bulb, the fuse was in place and the battery was connected. The metal end of the Festoon (or some tool you may have been using to remove the old bulb) shorted the base and blew the fuse.

If you pull the fuse *before* installing the bulb, then once the bulb is seated properly, re-insert the fuse, I'll bet dollars to doughnuts you'll be fine.

(Don't ask how I discovered this *could* be the problem )

Wavehogger

Thanks Bearcat94, Well I have electrical/electronic training from way back and I haven't taken the time to research this issue but yes one way for a fuse to blow is by shorting the line current (feed) directly to ground. Which isn't possible since I used my finger and skin has too much resistance to short to ground on a 12V DC circuit. And the festoon terminals in the trunk fixture don't have any metal areas directly around the bulb to short it to ground. A 2nd way a fuse will blow is when the circuit draws too much current (amperage), say I put in a bulb that used way more wattage than the 7.5amp fuse would accomodate, then it would blow.

Since i only had one extra 7.5a fuse on hand I didn't want to try again and blow another so I'm going to try it again, without the fuse in like you said when I get some extras and see what happens. It is possible that this circuit that was designed to have a certain amount of resistance/impedance so that it wouldn't short circuit, but the with the LED, that resistance was removed from the circuit. That's why the directionals blink hyper fast when LED's are put in, there is not enough resistance and you have to add some either by a flasher with added resistors or seperate ones. Most other circuits have some form either in the rheostats or switches, which let us replace other bulbs with LED's. A regular incandescent bulb creates a certain amount of resistance because the current has to pass through the filament to create heat, thus light. But if I have all LED's on the circuit and there isn't any other device in that line to create resistance, then it is possible that the fuse could blow because without any resistance/load it would be like connecting a wire directly from the positive to negative on the car battery. Hope that's clear enough for everyone.

Either way I was just checking to see if anyone else had changed their courtesy and trunk with LED's with success.

Bearcat94

Thanks for that. As I wsa typing I was thinking that the fuse had to work on both "sides" of the circuit - too much into the circuit = blown fuse; too much from the circuit = blown fuse.

Anyway, consider trying to put the lgiht in with the fuse removed, then re-install the fuse. I blew my lighting fuse putting in my trunk LED by shorting the bulb base. To prevent that in "round 2" that's what I did and it's been good ever since.

(I have a 3G, so there very well could be differences).

CleanCL

iTrader: (4)

I put LEDs into my vanity mirrors, door courtesy lights, trunk, and fog lights... and haven't had a single problem.

Wavehogger

Must have been a fluke.. I'll try again in the spring when I start my modding.

CleanCL

iTrader: (4)

By the way, whatever voltage is supposed to be going to those bulbs, is still going there. Just because you put LEDs into there, has NO effect on the car sending the voltage it wants to that socket. The LEDs you purchased should have come with resistors built-in. On the other hand if your car has a problem where it is sending too much voltage or too little, that is an issue totally unrelated to your LEDs.

Only the turn signals and brakes wiring is designed to 'look' for a certain amount of resistance because of safety issues. The door courtesy light/trunk light, the car could care less, it's just going to shoot whatever voltage it wants to that socket.