AMT Posted November 15, 2015 Share Posted November 15, 2015 Hello ...1992 MACK RD. Service Brake Lights not working. Tail/ directional / flashers/ and park brake lights are ALL working, hence probably eliminating the chassis wiring and bulbs. I'm thinking possible service brake light switch .....I've located two air pressure switches near steering column. Both when grounded activate low air pressure buzzers, not stop lights. ... Is there a separate service brake light switch? Where would it be located ? ......Thoughts , suggestions is appreciated AMT Quote Link to comment https://www.bigmacktrucks.com/topic/42679-service-brake-lights-not-working/ Share on other sites More sharing options...
felicello122 Posted November 15, 2015 Share Posted November 15, 2015 There should be one on the outside firewall behind the head left side, this usually is the one to change, just put one on my 2000 rd Quote Link to comment https://www.bigmacktrucks.com/topic/42679-service-brake-lights-not-working/#findComment-311570 Share on other sites More sharing options...
ekennedy21 Posted November 15, 2015 Share Posted November 15, 2015 there is one for the parking brake and one for the service brake. If you remove one and then step on the brakes air should come out the hole. If air comes out without stepping on the pedal then you have the parking brake switch. Air pressure makes the commotion on the service brake switch and interrupts the commotion on the parking brake switch. Good luck!! Quote Link to comment https://www.bigmacktrucks.com/topic/42679-service-brake-lights-not-working/#findComment-311577 Share on other sites More sharing options...
AMT Posted November 21, 2015 Author Share Posted November 21, 2015 Thanks for the good information .. you're right on the money ...switch location too .. bench tested the switch .. NG, replaced ...service brake lights now working BTW need to replace the radiator .. This truck has a snow plow PTO drive shaft through he radiator supports .. Do you know of a knowledgeable rebuilder I can contact ...AMT Quote Link to comment https://www.bigmacktrucks.com/topic/42679-service-brake-lights-not-working/#findComment-312363 Share on other sites More sharing options...
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