GMC Caballero Dome Light Bulb Size

The GMC Caballero dome light requires a bulb size of 561 for the interior lighting system. Data for the specified component covers the range from 1978 through 1979.

The year-by-year compatibility chart below provides a quick reference to verify the correct bulb size for your vehicle.

Bulb Size by Year Range

Years	Bulb Size
1978-1979	561

Bulb Specifications

Description	Bulb Size
ANSI standard (US & Canada). Festoon bulb, 44mm length, end-cap contacts. 12V, 12W.	561

Other Locations

Additional Notes

The 561 is a festoon-type bulb, meaning it is cylindrical in shape and makes electrical contact through metal caps at each end rather than through a base socket.
The 561 bulb follows ANSI standards, indicating it conforms to a recognized North American specification used across the United States and Canada.
The 561 operates at 12 volts and 12 watts, which is consistent with standard automotive electrical systems of that era.
The 561 has a 44mm length, which is a critical fitment factor for festoon bulbs, as the distance between the contact points in the housing must match the bulb length precisely.
The GMC Caballero used the 561 bulb size for the dome light across the 1978-1979 model years.