HELP!

Okay, so like forever ago I modded my factory security LED from red to blue. Well, after about a month, the first LED went out. So I bought a different one (brand & size). This one worked for a while, then went out as well. I ignored it for a while. I finally decided to fix it again. This time, back to normal. Here's my problem. I pulled out the socket, and attempted to install the original red LED. I put it, nothing. So, I had an idea. I took the 12v battery out of my garage door opener, hooked it to the LEDs (old and new) and they both worked. I am guessing something is dead in my wiring from the brain to the end of the LED socket. Does anyone know if there is any sort of "hidden" fuse to the LED light? I looked in the fuse panel, I checked them all. I looked at the alarm fuse under the hood in the little black box on the drivers side. They were all fine. Where would the "brain" for the factory alarm be? I was thinking I could go to the "source" and hook up a couple of wires and test the LED and find out if it's the wiring or the whole alarm brain is jacked up.

Oh, and other than the LED the alarm works fine. Any ideas?

 

Maybe you hooked up the LED leads backwords? Just a thought

 

Yeah, make sure the leds polarity is right, that it is around 3-4 VOLTS and that the resistor is still in the rubber socket that the led sits in. IF all else fails buy a cheap multimeter and measure for voltage. Multimeter is a very usefull tool. I couldn't live w/o mine. I usecd the Radioshack led part # 276-316 for my security light. VERY BRIGHT!!

 

Thanks to both of you,

Actually, I originally hooked the LED up both ways just to make sure, and nothing. But the same LED works with the battery, so it must be the wiring or alarm brain. (using the word "must" very freely, as in, it must be this way because I don't know any better, "must" is subject to correction)

I don't have a multimeter, so I guess I'll go get one today and see what comes up.

 

Yeah, use the multimeter also make sure that the resistor is still in the rubber socket and hasn't fallen out. I was curious about your leds in the A/C unit. DO you have the AUTO a/c unit? If so did you just change the ones that show a button is pressed or did you hook up the leds so that the buttons lettering lights up blue? Thanks.

 

About the resistor...uh, is it really important? 'cause I got rid of it a long time ago, like the first time I replaced the LED. I got mad at the little gray rubber thing so I just directly soldered my LEDs to the posts in the socket. Bad idea? If so, can I replace the resistor, and if so to that, why type/kind is it? The LEDs did work for a while without this resistor on it. I guess I could replace it, and just solder it back on. Was it on the + or - terminal?

I have the plain jane manual A/C unit. I replaced the lights that are below the push buttons, the ones that light up showing the selection you have made. They are normally green, they are now blue. The lettering is actually done with very tiny light bulbs with little blue condoms on them. I don't think anyone has replaced those yet.

edit: WOO HOO! My 50th Post!

 

Yeah, that little resistor is very important. If you have a 4 volt led and you supply it with the 12 volt led output of the alarm you cook your new led. The math works like this, and the resistor is known as a 'dropping resistor' because it eats up the unwanted voltage. Existing Voltage - Led voltage = Voltage to be dissapted. In this example 12 - 4 = 6. So you have 6 volts to eat up. More than likely your led draws .02 amps. So to calculate the resistor value divide the voltage by the current to get resistance. (ohm's law) For our example 6/.02=300 So you will need to solder a 300 ohm resistor in series w/ the led. The actual resistance of the resistor from the factory is around 600 ohms if I remember right. You will be fine using anything between 300 - 600. I know Radioshack sells a 330 ohm 1/4 watt resistor and that should be fine.
Thanks for the info. on the A/C unit. I have the Auto unit and have tried everything to get that shate blue:leds, glass stain etc. It's close but not like my switches. Good luck w/ your security light.

 

Okay...I bought myself a multimeter. Pretty nifty device.

Anyway. I hooked it directly to the two wires that supply power to the LED. It's an auto sensing multimeter, but the auto sense didn't work. So I put it on DC - Volts, correct? I hit the lock button, which would cause the LED to be solid on. The meter registered .002V. Does that sound correct? I know the meter works properly since I hooked it to the light bulb socket in the door, which registered something around 13.7V, which I am also assuming is correct.

I will run to radioshack tomorrow and go ahead and get a new resistor so I have it. Would the resister go on the positive or negative side?

Thanks again!

 

Would the resister go on the positive or negative side?

Thanks again! [/B][/QUOTE]

I don't think it matters - but I have always put it on the positive side. If you look inside the leds housing you'll see two posts that resemble Pl The l is the positive side. Hope your light works. As far as the reading of .002 that is not right. You probably tried measuring the voltage while the led would have been flashing. It is hard for your meter to record the actual voltage, since it's so quick. TO get a better measurement, try getting inside the car, opening the door, close the door and lock it but DON'T push the lock button on your remote, and then for about thirty seconds the led should read a steady 12 volts.

 

Just a note, 12-4 = 8 so your calculations are just a bit off, but probably wont make much of a difference

put the resistor on the anode (+) side of the LED and you'll be fine

 

Okay, another try.

I once again connected my tester. I sat in the car, hit the lock button. The test still read .002, sometimes it would jump to .004 or .005 for a second, but would always be steady at .002. I unlocked the car. Tester said .000. Hit the lock button on the remote, doors locked, dome light went out, hazards blinked, meter read .002 again.

So, I'm thinking there is something wrong with the alarm. Would you (or anyone else) have any idea where the LED wires (yellow and green) "end up" in the car. I figure I could go to the source and check it there, maybe the wiring has gone bad somewhere?

This kinda puts a whole new light on the joke how many [whatevers] does it take to change a light bulb. UGH!

Thanks again for any help!

 

I guess that's why I'm back in school. DOH!!! Yeah, you're right - it still shouldn't make too much difference. 8/.02 = 400 ohms. So still in range of 300 - 600. I'm so dumb
Also, BPinson - I don't know what color the wires are but the led is run off of the bcu which is near the ecu in the center console. I would still try the led/resistor first. That's easier than getting access to the bcu and if it works then you're done, if it doesn't then check the bcu. I'll look in my FSM when I get a chance to see if I can get the wire colors at the bcu. Good luck.

 

Damn.

Nothing...

I got myself a resistor and soldered it onto the + side of the LED assembly. I then used my 12V battery and hooked it up to the LED, I got a light. So, I went down to my car. I hooked the LED up, with the resistor still soldered inline, hit the lock button on the remote, and nothing. Still no LED.

Ugh. I'm tired now, I'm going to bed. If there are any new ideas, I am open to trying them.

Thanks as usual.

 

Try reversing the led wires in the car. Other then that I would suspect you damaged the led output of the alarm by running the previous led without the resistor. I'm still looking for my fsm - but if the led doesn't work I would assume the led output was fried. Sorry to say.

 

Thanks. I tried it both ways. I kind of figured that I may have done something to the alarm. I guess I will have to get used to not having an LED. I could always get an aftermarket alarm, but to be honest, my Max has high mileage, several scratches, needs new tires, a tune up, and is still financed. Sad that I would get more from the insurance company than I would from a car dealership. Not that I want anything to happen to my car...I just don't want to spend any more money than I have to so that I can just trade it in for a new one! Woo hoo!

Can the alarm brain be replaced on the car? Such as just calling and getting the new part, plugging it in and reprogramming the remotes? The bad thing is the more I think about it the more I figure it's a waste of money to buy a new brain just for the LED. I think I am going to leave it as is...I think I will just go buy some new speakers...Yep...that's what I'll do.

Thank you very much for all your help. It's been a good lesson in LED/electrial technology.

 

Sorry to hear your luck. Enjoy those new speakers. BTW, when you're looking at speakers you may ask about flashing led's. I've seen some that just need 12 volts and they blink on their own. They even come in crazy colors. THis could simulate your alarm's led???
I don't know if you can buy a replacement bcu - it probably wouldn't be worth it. Glad to help with what I could. Take care.

 

Regarding your LED, nobody mentioned the fact that without the dropping resistor, you were pulling excessive current from the circuit that lights and flashes the LED. Most likely you have burnt out that circuit on the brain itself. Your not getting any voltage from the brain because the circuit is now dead. Sorry but I think your S.O.O.L.

Radio Shack does sell a flashing led. You could just hook that baby up to 12V, use a dropping resistor if you need to step down the voltage to whatever the LED requires. Hook a toggle switch up to it and just manually turn on the flashing led.

Hey the thieves will never know.......