OBC Light FIX! (modification)
11-03-2004, 06:46 PM
#1
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Thread Starter
OBC Light FIX! (modification)
Having endured an intermittent on board computer light for the last six months (more off than on), today I decided to fix it.
I first removed the Tach by disconnecting the battery, then leaving the car for half an hour to let the Air bag discharge. Then removed the steering wheel, stalk surrounds and then pulled the tach out. Easy so far.
I then removed the back of the Tach and simply changed the bulb AND the transistor (BC327) just to be sure it would work when it went back together!
Long story short; it worked for less than 30 seconds!
Removed it all again to perform the following modification:
Took the back off the tach as you would to change the bulb. I then unscrewed the PCB that holds the indicator and high beam warning lights and put it to one side.
I then carefully cut the tracks on the pcb that provide power to the OBC light, soldered two three inch wires to the bulb cut out (on the PCB) and connected the other ends to the tracks that lead to the back lighting bulbs of the tach.
Once put back together, the OBC now lights up with the rest of the dash lights and is also fully dimable (unlike the original)! Sorry i have no pictures but it's really easy and took no more than 45 mins.
Any questions let me know.
Alan
I first removed the Tach by disconnecting the battery, then leaving the car for half an hour to let the Air bag discharge. Then removed the steering wheel, stalk surrounds and then pulled the tach out. Easy so far.
I then removed the back of the Tach and simply changed the bulb AND the transistor (BC327) just to be sure it would work when it went back together!
Long story short; it worked for less than 30 seconds!
Removed it all again to perform the following modification:
Took the back off the tach as you would to change the bulb. I then unscrewed the PCB that holds the indicator and high beam warning lights and put it to one side.
I then carefully cut the tracks on the pcb that provide power to the OBC light, soldered two three inch wires to the bulb cut out (on the PCB) and connected the other ends to the tracks that lead to the back lighting bulbs of the tach.
Once put back together, the OBC now lights up with the rest of the dash lights and is also fully dimable (unlike the original)! Sorry i have no pictures but it's really easy and took no more than 45 mins.
Any questions let me know.
Alan
11-03-2004, 06:54 PM
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Join Date: Feb 2004
Location: Boone, NC
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How readable is the display during the daytime when the dash lights are off?
When mine was in the flashing point of failure, if the light was off I could barely read the display even in the daytime. At this point, it is in the always on mode of failure. I can easily read the numbers day or night. It's just that the light stays on continuously, even when parked with the ignition off. Since I drive the car every day, I havn't worried about it too much since the buld is such a low wattage. Whenever the buld burns out, I guess I'll get around to fixing the problem.
When mine was in the flashing point of failure, if the light was off I could barely read the display even in the daytime. At this point, it is in the always on mode of failure. I can easily read the numbers day or night. It's just that the light stays on continuously, even when parked with the ignition off. Since I drive the car every day, I havn't worried about it too much since the buld is such a low wattage. Whenever the buld burns out, I guess I'll get around to fixing the problem.
11-03-2004, 08:00 PM
#3
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Thread Starter
I always have my lights on during the day as it greatly improves my visibility to others.
You could simply wire the bulb up to the ignition instead of the dash lights though.
You could simply wire the bulb up to the ignition instead of the dash lights though.
07-15-2014, 11:12 PM
#4
I ran into the same issue as Alan. I changed out the transistor twice and it only lasted a little while each time.
I will caution you all to look carefully at the bulb function before you get power from it. On the first try I jumped from a turn signal bulb because it was easier to get to the solder connections on the PCB but it blinked on with the turn signal! I pulled it apart again and found the correct bulb (yellow base for constant switch-on backlighting). It's tricky to solder to this so here is what I did:
1. Remove the back of the gauge as per normal instructions. Remove the three screws and carefully pull out the PCB that holds the turn signal, high beam, backlights etc. It's the next layer of board that you see still in the main gauge body (i.e. this is not the same board that holds the transistor). Note that it has some sliding contact pins for the tach input so lift straight up to remove.
2. Melt a little hot solder blob on the metal semicircular contact on the PCB where the bulb gets power. Make sure you attach the wire at a location on the contact that allows you to remove the bulb. If it's not clear, remove the bulb and observe which way it rotates so you can see where it is clear to attach a wire. If you drip a little solder blob onto the board before trying to attach the wire it goes easier. There is more room on the yellow-base backlight bulb from which you will borrow power so it is easier. With that part done, I carefully routed the wires so they could avoid all the other pieces and end up near the OBC backlight bulb, and re-attached the PCB to the rest of the gauge housing.
3. Things were a little tighter for the green-base OBC backlight bulb because the base covers the whole contact, so I had to set the wire next to it and spread the solder outward to catch the wire just outside the perimeter. Then I smoothed it over where the bulb contacts so it can engage fully. I also cut the tracks to this bulb so it could not longer receive or send power to the transistor etc.
4. With that, I reattached the back of the gauge and wiggled it back into the dash. You can do this without pulling the wheel if you use something like Armor-all to slick up the plastic steering trim and gauge rim. Then gently work the gauge out just far enough to remove the rubber gasket. That buys you just enough space to wiggle it out and start heading to the right. You can push down on the steering wheel to free up more space and it will just barely make it out. Be careful not to force it or it will damage the soft alloy bezel. Reinstall is the opposite, including putting the rubber gasket on just before it goes all the way in. Good luck!
I will caution you all to look carefully at the bulb function before you get power from it. On the first try I jumped from a turn signal bulb because it was easier to get to the solder connections on the PCB but it blinked on with the turn signal! I pulled it apart again and found the correct bulb (yellow base for constant switch-on backlighting). It's tricky to solder to this so here is what I did:
1. Remove the back of the gauge as per normal instructions. Remove the three screws and carefully pull out the PCB that holds the turn signal, high beam, backlights etc. It's the next layer of board that you see still in the main gauge body (i.e. this is not the same board that holds the transistor). Note that it has some sliding contact pins for the tach input so lift straight up to remove.
2. Melt a little hot solder blob on the metal semicircular contact on the PCB where the bulb gets power. Make sure you attach the wire at a location on the contact that allows you to remove the bulb. If it's not clear, remove the bulb and observe which way it rotates so you can see where it is clear to attach a wire. If you drip a little solder blob onto the board before trying to attach the wire it goes easier. There is more room on the yellow-base backlight bulb from which you will borrow power so it is easier. With that part done, I carefully routed the wires so they could avoid all the other pieces and end up near the OBC backlight bulb, and re-attached the PCB to the rest of the gauge housing.
3. Things were a little tighter for the green-base OBC backlight bulb because the base covers the whole contact, so I had to set the wire next to it and spread the solder outward to catch the wire just outside the perimeter. Then I smoothed it over where the bulb contacts so it can engage fully. I also cut the tracks to this bulb so it could not longer receive or send power to the transistor etc.
4. With that, I reattached the back of the gauge and wiggled it back into the dash. You can do this without pulling the wheel if you use something like Armor-all to slick up the plastic steering trim and gauge rim. Then gently work the gauge out just far enough to remove the rubber gasket. That buys you just enough space to wiggle it out and start heading to the right. You can push down on the steering wheel to free up more space and it will just barely make it out. Be careful not to force it or it will damage the soft alloy bezel. Reinstall is the opposite, including putting the rubber gasket on just before it goes all the way in. Good luck!
07-19-2014, 05:27 PM
#6
Pro
Thread Starter
When I read this I thought - wow - I seemed much better educated than I feel now!
Still have the baby in the garage and the OBC light hasn't given me any trouble since!
Still have the baby in the garage and the OBC light hasn't given me any trouble since!
10-28-2019, 10:50 AM
#7
I ran into the same issue as Alan. I changed out the transistor twice and it only lasted a little while each time.
I will caution you all to look carefully at the bulb function before you get power from it. On the first try I jumped from a turn signal bulb because it was easier to get to the solder connections on the PCB but it blinked on with the turn signal! I pulled it apart again and found the correct bulb (yellow base for constant switch-on backlighting). It's tricky to solder to this so here is what I did:
1. Remove the back of the gauge as per normal instructions. Remove the three screws and carefully pull out the PCB that holds the turn signal, high beam, backlights etc. It's the next layer of board that you see still in the main gauge body (i.e. this is not the same board that holds the transistor). Note that it has some sliding contact pins for the tach input so lift straight up to remove.
2. Melt a little hot solder blob on the metal semicircular contact on the PCB where the bulb gets power. Make sure you attach the wire at a location on the contact that allows you to remove the bulb. If it's not clear, remove the bulb and observe which way it rotates so you can see where it is clear to attach a wire. If you drip a little solder blob onto the board before trying to attach the wire it goes easier. There is more room on the yellow-base backlight bulb from which you will borrow power so it is easier. With that part done, I carefully routed the wires so they could avoid all the other pieces and end up near the OBC backlight bulb, and re-attached the PCB to the rest of the gauge housing.
3. Things were a little tighter for the green-base OBC backlight bulb because the base covers the whole contact, so I had to set the wire next to it and spread the solder outward to catch the wire just outside the perimeter. Then I smoothed it over where the bulb contacts so it can engage fully. I also cut the tracks to this bulb so it could not longer receive or send power to the transistor etc.
4. With that, I reattached the back of the gauge and wiggled it back into the dash. You can do this without pulling the wheel if you use something like Armor-all to slick up the plastic steering trim and gauge rim. Then gently work the gauge out just far enough to remove the rubber gasket. That buys you just enough space to wiggle it out and start heading to the right. You can push down on the steering wheel to free up more space and it will just barely make it out. Be careful not to force it or it will damage the soft alloy bezel. Reinstall is the opposite, including putting the rubber gasket on just before it goes all the way in. Good luck!
I will caution you all to look carefully at the bulb function before you get power from it. On the first try I jumped from a turn signal bulb because it was easier to get to the solder connections on the PCB but it blinked on with the turn signal! I pulled it apart again and found the correct bulb (yellow base for constant switch-on backlighting). It's tricky to solder to this so here is what I did:
1. Remove the back of the gauge as per normal instructions. Remove the three screws and carefully pull out the PCB that holds the turn signal, high beam, backlights etc. It's the next layer of board that you see still in the main gauge body (i.e. this is not the same board that holds the transistor). Note that it has some sliding contact pins for the tach input so lift straight up to remove.
2. Melt a little hot solder blob on the metal semicircular contact on the PCB where the bulb gets power. Make sure you attach the wire at a location on the contact that allows you to remove the bulb. If it's not clear, remove the bulb and observe which way it rotates so you can see where it is clear to attach a wire. If you drip a little solder blob onto the board before trying to attach the wire it goes easier. There is more room on the yellow-base backlight bulb from which you will borrow power so it is easier. With that part done, I carefully routed the wires so they could avoid all the other pieces and end up near the OBC backlight bulb, and re-attached the PCB to the rest of the gauge housing.
3. Things were a little tighter for the green-base OBC backlight bulb because the base covers the whole contact, so I had to set the wire next to it and spread the solder outward to catch the wire just outside the perimeter. Then I smoothed it over where the bulb contacts so it can engage fully. I also cut the tracks to this bulb so it could not longer receive or send power to the transistor etc.
4. With that, I reattached the back of the gauge and wiggled it back into the dash. You can do this without pulling the wheel if you use something like Armor-all to slick up the plastic steering trim and gauge rim. Then gently work the gauge out just far enough to remove the rubber gasket. That buys you just enough space to wiggle it out and start heading to the right. You can push down on the steering wheel to free up more space and it will just barely make it out. Be careful not to force it or it will damage the soft alloy bezel. Reinstall is the opposite, including putting the rubber gasket on just before it goes all the way in. Good luck!
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11-15-2019, 03:18 PM
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