radio very dim, new bulb didn't fix it

[hammer2]

2000 SE the radio/clock was very hard to see. had to have sunlight hit it just right. read around here and elsewhere and ended up replacing the backlight with a radio shack bulb. maybe helped a little but still not very good so shelled out $8 for the GM bulb. still not good. the bulb is good, tested it with battery. what else could it be? you can see display if you get right next to it and if lighting is just right.

[richtazz]

the PCB that the bulb plugs into may be bad.

[doctorhrdware]

IF you can measure the voltage at the pcboard, you should get approximately 12Vdc at the connection for the display lamp. That will also dim with the interrior light dimmer. If the voltage is missing check the wirring going to the radio. There might be a problem with the wire that supplies the voltage for the display back light. Does the bulb light up at all. Also are the rest of the dash lights, on and are they bright?

[hammer2]

can't really measure the voltage because to get to the contacts, you have to take face plate off and there are several connectors that get disconnected as faceplate comes off. so unless you want to run jumpers from all these pins and hope that nothing shorts, you can't easily do this. all other lights work and brightness is fine. just the display is dim. I still have the plastic dash off. when it is night, if I trick the sensor into thinking it is daytime, I can see a white light come on through the holes in top of radio. then if I remove the light shining on sensor, after a while the light goes out. I think I am gonna remove the bulb and see what happens to determine if that is the bulb that is lighting up. should the backlight bulb be lit all the time? or only during daytime? let you know of results.

[hammer2]

OK I had it wrong. here is what happens
at night if turn radio on I can see a white light through the holes in top and L side of radio. it dims when I dim dash lights. if I then trick the sensor into thinking it is daylight, the light goes out. and when I removed the brand new LCD backlight--nothing changed! so I don't think the backlight is coming on, and the other light I see is the backlighting for buttons on the radio--they wouldn't need backlighting during daytime and that is why they go out when I trick sensor. The LCD WOULD need backlighting during day-actually brighter light during day. it should then dim when it is nighttime, and dim further with the dash dimmer also. at least that is how i remember it working.

so I guess something else wrong (PCB?) not likely worth fixing.

[rkvons]

Originally Posted by hammer2

OK I had it wrong. here is what happens
at night if turn radio on I can see a white light through the holes in top and L side of radio. it dims when I dim dash lights. if I then trick the sensor into thinking it is daylight, the light goes out. and when I removed the brand new LCD backlight--nothing changed! so I don't think the backlight is coming on, and the other light I see is the backlighting for buttons on the radio--they wouldn't need backlighting during daytime and that is why they go out when I trick sensor. The LCD WOULD need backlighting during day-actually brighter light during day. it should then dim when it is nighttime, and dim further with the dash dimmer also. at least that is how i remember it working.

so I guess something else wrong (PCB?) not likely worth fixing.

You should look carefully at how the bulb is mounted. Mine was originally soldered in and had to be un-soldered and then twisted to remove it. You could solder a couple of pieces of wire where your bulb is supposed to hook up and bring them out of the radio. Then install the radio and once it's on, measure the voltage across this new set of wires. Did you verify that your old bulb was burned out? I would make sure the bulb contacts are connected to the PCB contacts.