Inside lighting problems
mamacows
07-06-2006, 08:18 PM
Just recently our 1998 GMC safari mini van has lost the dashboard lights. We started looking around and noticed that the rear stereo controls aren't lighting up and now the rear running lights don't light up. I have checked fuses and none seem to be blown...is there anybody out there that can point me in the right direction please!!
Thanks
Thanks
old_master
07-14-2006, 09:26 PM
Welcome to the forum! The absolute best way to test fuses is with a voltmeter. The fuses do not have to be removed to test them. Testing in this manner will also check the integrity of the terminals and connections in the fuse panel itself.
The headlamp switch is supplied with power through a fusible link. If the headlamps are working, the fusible link is good. The switch supplies power for the tail lights through a fuse and then on to the tail lamps. The instrument lamps are supplied power from the tail lamp circuit and then through the dimmer switch, and then on to the lamps.
The two fuses for tail lamps and instrument lamps will only have power when the headlamp switch is on. Check your owner’s manual for the fuse location in the fuse panel. Connect the voltmeter negative lead to a good clean body ground. Connect the positive lead to one side of the fuse and turn the headlamp switch on and off. You should see the voltage change from zero to battery voltage as you turn the switch on and off. Use this same procedure for each terminal of the two fuses.
It's possible that the headlamp switch is unable to supply power to the tail lamps and as a result, power can not be supplied to the instrument lamps. If this is the case, the headlamp switch will need replacement. If testing the fuses shows that power is being supplied to both fuses, and the lights are still inoperative, there is an open circuit in the tail lamp AND instrument lamp circuits. The odds would be astronomical that two problems occur at the same time, especially with circuits so closely related to each other. If the vehicle has an aftermarket radio, or a trailer wiring harness, after checking fuses, I would concentrate efforts in those areas. Hope this helps.
The headlamp switch is supplied with power through a fusible link. If the headlamps are working, the fusible link is good. The switch supplies power for the tail lights through a fuse and then on to the tail lamps. The instrument lamps are supplied power from the tail lamp circuit and then through the dimmer switch, and then on to the lamps.
The two fuses for tail lamps and instrument lamps will only have power when the headlamp switch is on. Check your owner’s manual for the fuse location in the fuse panel. Connect the voltmeter negative lead to a good clean body ground. Connect the positive lead to one side of the fuse and turn the headlamp switch on and off. You should see the voltage change from zero to battery voltage as you turn the switch on and off. Use this same procedure for each terminal of the two fuses.
It's possible that the headlamp switch is unable to supply power to the tail lamps and as a result, power can not be supplied to the instrument lamps. If this is the case, the headlamp switch will need replacement. If testing the fuses shows that power is being supplied to both fuses, and the lights are still inoperative, there is an open circuit in the tail lamp AND instrument lamp circuits. The odds would be astronomical that two problems occur at the same time, especially with circuits so closely related to each other. If the vehicle has an aftermarket radio, or a trailer wiring harness, after checking fuses, I would concentrate efforts in those areas. Hope this helps.
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