Interpretation ID: nht89-3.55

TYPE: Interpretation-NHTSA

DATE: December 15, 1989

FROM: R.R. Chestnut -- Supervisor, Modified Vehicle Engineering Dept, Ford Motor Company

TITLE: Re Splicing Into The Stop Lamp Electrical Circuit

ATTACHMT: Attached to memo dated 6-6-90 from Tekonsha Engineering Company; Also attached to letter dated 8-31-78 from J.J. Levin, Jr. to L.F. Henneberger; Also attached to letter dated 5-2-84 from F. Berndt to L.F. Henneberger; Also attached to letter da ted 11-30-81 from F. Berndt to K.G. Moyer (A23; Redbook 3; Std. 108); Also attached to letter dated 9-10-90 from P.J. Rice to L.F. Henneberger (A36; VSA Sec. 103 (d); Std. 108); Also attached to letter dated 6-22-90 from L.F. Henneberger to P.J. Rice (OC C 4927)

TEXT:

Splicing Into The Stop Lamp Electrical Circuit

This bulletin emphasizes the importance of QVM Bulletin #8, issued October 13, 1989, which cautions builders concerning altering of connecting to stop lamp circuits. The stop lamp switch and related wiring not only control the stop lamps, but also provi de the brake on/off input to the electronic modules of the EEC, EAOD, speed control, and anti-lock brake systems. Splicing into a location that interrupts the signals to these modules can interfere with their proper functioning, including:

1. Affecting EFI engine idle speed quality 2. Preventing the EAOD torque converter clutch from applying at throttle openings less than half throttle 3. Deactivating anti-lock brake system operation 4. Preventing the speed control from disengaging upon braking

Attachments I, II, and III of this bulletin illustrate acceptable locations to splice into the stop lamp circuits of Econoline and F-Series vehicles.

Note that when stop lamps are installed in addition to the OEM stop lamps, the additional load must not exceed 6 amps (3 bulbs), yielding a total circuit draw not exceeding 10.4 amps (5 bulbs). Loads exceeding 10.4 amps can damage the stop lamp and/or t urn signal switch.

If you have any questions regarding this issue, please call the Body Builders Advisory Service Hotline on 1-800-635-5560.