Got another bug knocked off the screen... my truck is finally coming together! Anyways, I had my airbag idiot light on for awhile now. I noticed the PAS (passenger airbag switch) wasn't lighting. I just figured it was a bad switch. For awhile, there was no airbag idiot light, but there was an annoying ding that would come up occasionally... come to find out, since it couldn't light, it would ding. A new bulb and the dinging went away. Now, I just had an idiot light. I put up with it for awhile, but I got AE and found out that there was a specific code for my problem... the bulb in the switch was burned out. Well, after some research, I found out this was common. The common fix was to just get another 12V lamp and solder it onto the board. But I didn't wanna fool with it again so I decided I was gonna try to make an LED work. Now, I know an LED won't run off 12V... it's more like 2.1V (at least the yellow one I got from Radio Shack was that way). There are numerous calculators online that will give you a resistor value to use an LED with any given voltage. My specs were a 14V power source, 2.1V LED, and 30mA MAXIMUM current. I came out with a 470ohm 1/2W resistor. When all was said and done, I checked the voltage while running the truck's RPM's up and the voltage across the LED was at 1.9V and 3.9mA... that's JUST under the ratings. I took some pictures so I hope that you'll get a good idea of how I did it. I'm picky when I do things and I like to make them look like they were meant to be that way so you don't have to go as far as I did. Anyways, enjoy!

Here's the switch... to get it off, you have to pop the bezel off and undo the connector and three screws that hold the switch onto the back of the bezel. As a quick note, there are two screws that hold the bezel on that're in the top of the radio cavity. I took my screws out since I have an aftermarket radio with the adapter because removing the adapter too many times will break it. My truck is in some pretty harsh places and I have had NO problems at all. But anyways... just so you know. Here's the switch (note the top is popped off):




Here's the board... there's a yellow filter on the bulb that you have to roll off the bulb inside-out like you would your sock. Hang onto it because you'll need it... I'll explain later. Looking it it, the switch just ain't worth the $100+ the dealer wants for it... there's nothing to the switch!


Now, the bulb is in a circuit of its own and isn't tied in with anything else on the board. There are two copper strips in the board, each running to a different pin in the connector. What I wanted to do was solder the resistor on the bottom of the board using two existing solder points, but there would be an "easy path of travel" if I ran it in parallel with one of the copper strips. So, I had to create a break in it... the pictures will help to better explain. It's fairly easy to do... just take a sharp blade and scour the copper strip in two places. Then peel the strip off the board like you would if you were peeling an apple. See where I peeled it off?




Then, I just soldered the resistor in using two existing solder joints... it looks like it belongs there. Now, for those of you who are keen, yes, that's a 560Ohm resistor in the picture. I had entered different info into the calculator I used because the values I got off the internet for LEDs were different than the LED's I got from Radio Shack. After refiguring the values, I got 470ohm. The voltage in my circuit was much closer to the LED's specs than it was with the 560ohm (it had plenty of headway in regards to the LED's ratings). So, I ended up putting in a different value. I had tried to increase the resistance of the resistor so the LED wouldn't glow when off, but I was up to 1Mohm before it went out in the "On" position. When I turned the switch "Off", you could hardly see the LED light! I ended up remembering the yellow filter that was on the other bulb and when I put that on the LED, it fixed the problem and the LED worked like a charm!


Then, it's just as simple as soldering the LED in where the bulb was. Note the black dot it put on the side of the board nearest to the camera... that's the negative side of the circuit (I rung it out with a voltmeter). Make sure that you put the shorter terminal of the LED on this side. Otherwise, it won't work. The positive terminal of the LED is the longer terminal.


Make sure to put that yellow filter back on the LED before you reinstall it. The reason is because I tried the thing without the filter and there was a yellow circle in the face of the "Off" indicator when in the "Off" position and there was also a faint glow when the switch was in the "On" position. The reason this is is because there's always a slight current going through the system to make sure the bulbs aren't blown, but also, and LED takes ALOT less current to light than a bulb. The filter makes the slight "On" glow not visible and it also makes the LED fill out the face of the lens when in the "Off" position. Just roll the filter back on the way you took it off:


I'm VERY pleased with this mod... I won't have to deal with it burning out again and it saved me a TON of money! As far as supplies go, here's what I bought:

Pack of 5mm Yellow LEDs
Pack of 470ohm 1/2W Resistors

Less than $5-worth of stuff! Took some time to figure out, but it worked great!

While I was in the mood, I replaced the LED in my headlight switch as well because it was getting pretty dim... it had to be VERY dark out to be able to see it. Here's a few pictures of where it is located in regards to the switch:




It also uses a 5mm LED, but this one is green... it made a BIG difference and the switch is now obvious at night. But anyways, let me know if I can clarify anything!

 

Hey Jon thanks just did this in a half hour and saved 100 bucks

 

GREAT!!!!!!
you saved me a BUNCH of money on this!
one question:
how does the switch attach to the dash?
can i get it out without taking the dash apart by reaching through the radio hole?
sorry for the thread revival but this may help a lot more people anyway

 

No, you can't... I wish it was that easy! You have to pull the radio out and undo those to screw on the underside of the top edge of the radio opening. Then you have to pull the bezEl out enough to get a nut driver or ratchet in there to undo the screws that hold the PAS in there (it's two or three... can't remember). Also, undo the harness and then you're set!

 

i answered my question

 

worked great! the hardest part was getting the courage to pull on the dash cover.

 

JonathanN, Thanks for posting this. Worked great on my 2000 F250.

 

Thanks for doing the hard work on this one Jonathan. Was very simple to do after reading your post. I'd say took me 30 minutes all together. Very please with a less than $5 fix, compared to the dealership part/price.

Airbag light is off

Edit: I went with a yellow LED from Radioshack. This eliminated the need to mess with the yellow roll-on cover.

 

Now that's a good idea... do you have an issues with that really slight glow when the "off" indicator is off? I do, but I'm not sure how to eliminate that... the PCM must use a constant current to determine whether or not the system (indicators and all) are working correctly. While not much current, it's enough to light an LED. Kinda aggravating!

 

I remember reading this from your first post, I thought that was why the resistor was added. I've not looked at mine in the dark, but I have yet to notice any glow from the light unless the passenger airbag is de-activated. Do you have an aftermarket head unit? The glow or light may be coming from another component possibly....

Funniest thing about my switch was the bulb 'apeared' to be good. The airbag trouble code is what made me cut the incandescent off and go with the LED. I plan on doing the headlight switch in the future.

 

The resistor is because the LED uses less current, but it also uses a quarter of the voltage as well. However, the "test voltage" that's constantly on the system still will light the LED ever so slightly. I can only see it at night and I have to be looking for it... that's just me being picky, though. I decided to use a potentiometer to see what I'd have to use for a resistor to make the LED be completely "out" and it was quite a bit, actually. However, because the LED uses so little current, when I'd turn the PAS off, the LED would barely light! So, yeah... kinda funky.

 

Nice write-up! Reps sent.

 

FYI, i put in a socketed 12v bulb so that no resistors were necessary when i did mine.
i just de-soldered the bulb and put in one that had a socket. that way if it ever burned out again, i can just replace it.
i'd have used an LED but i didnt have one laying around, whereas i had about 50 regular bulbs laying around from various dis-assembly projects

 

I might have to try that sometime if I ever run across another truck...

 

A bulb is only easier if you don't want to solder two more connections. No doubt it will work, but the long life of the LED is what I was after. Never again will I have to pull that box apart

Also, did you install a resistor into the headlight LED? Would like to see any more pics you have related to the headlight switch if you have any.