Ford B-600 High Beam Indicator Bulb Size

Additional Notes

• The Ford B-600 high beam indicator uses two distinct bulb sizes across its model years: the 37 and the 194, both of which are ANSI-standardized miniature wedge bulbs for the US and Canadian markets.
• The bulb 37 follows the T5 form factor and operates at 12V with a rated power of 1W, placing it among the lower-wattage indicator bulbs in automotive applications.
• The bulb 194 follows the T10 form factor and operates at 12V with a rated power of 3.78W, making it notably higher in wattage than the 37 despite both serving the same indicator function on this vehicle.
• T5 and T10 designations refer to the tubular envelope width of the bulb, measured in eighths of an inch, meaning the 194 has a physically larger envelope than the 37. These two types are not interchangeable due to differences in both physical size and wattage.
• The Ford B-600 used the 194 bulb for the high beam indicator across the 1980-1989 model years, with the exception of 1990 and 1991.
• The 37 bulb was specified for the 1990, 1992, 1993, and 1994 model years, while 1991 returned to the 194 specification, indicating that the two bulb types alternated during this period rather than representing a clean transition.
• Because the 37 and 194 share the same wedge base style but differ in envelope size and wattage, substituting one for the other risks fitment failure or incorrect electrical load on the indicator circuit.