'70 radio lamp not working

[Chris H.]

Hello, I have stock AM/FM radio, (non stereo) and the internal bulb is not working and I presume it's blown (no light even with radio on).

Can I replace the bulb without removing the radio, or does the radio need to come out?

Thanks, Chris

[Jack H.]

Re: '70 radio lamp not working

The main power connector to your radio has three lead wires in it. The center is ground and the two outer leads are power lines. One is battery voltage to run the radio and the other services the dial lamp (a GE 1893 bulb internal to the radio chassis--YES, you have to pull the radio and crack open the chasis to replace the lamp).

The lamp power lead varies in voltage based on the rheostat setting of your headlight switch. This makes all dash illumination vary in lockstep. I'd start first by checking the integrity of radio lamp's power lead, maybe you'll get lucky and have a simple wiring problem to fix and NOT have to pull the radio to replace the lamp...

Disconnect the 3-lead power connector from the radio. Measure voltage between the center lead (ground) and the two outer leads. One should remain constant (battery voltage) while the other varies in lock-step to the position of the headlight dimmer switch setting.

[Chris H.]

Re: '70 radio lamp not working

Jack, thank you for the in depth response. I was afraid I'd have to remove the radio. Chris