Ford Aerostar Parking Brake Indicator Bulb Size

Additional Notes

• The Ford Aerostar parking brake indicator uses two distinct bulb types across its production run: the 194 and the 37, both of which are ANSI-standard miniature wedge bulbs rated for 12-volt systems.
• The 194 bulb follows the T10 wedge form factor and draws 3.78 watts, making it the higher-wattage of the two types specified for this application.
• The 37 bulb follows the T5 wedge form factor and draws 1 watt, a notably lower power draw than the 194.
• Although both bulbs share the same 12-volt operating voltage, their differing wattages and T10 versus T5 form factors mean they are not interchangeable with one another.
• The 194 bulb is specified for the 1994-1997 model years, as well as for 1988-1989.
• The 37 bulb is specified for 1986-1987, 1990-1992.
• The 1993 Ford Aerostar is the only model year in these specifications where the correct bulb size depends on instrument cluster type, with the 37 applying to vehicles fitted with a digital instrument cluster and the 194 applying to those without one.
• The T5 designation of the 37 bulb refers to a tubular glass envelope that is 5/8 of an inch wide, while the T10 designation of the 194 refers to a 10/8-inch (or 1.25-inch) wide envelope, reflecting a physically larger bulb body.
• Both the 194 and 37 bulbs use a wedge base, meaning the electrical contacts are formed by the glass pinch at the base of the bulb rather than by a separate metal cap or bayonet fitting.
• ANSI standardization for both bulb types indicates that conforming replacements from different manufacturers are expected to share the same electrical and physical specifications within the US and Canadian markets.