Re: stop light switch 56 pat

Posted by Bowman Davis On 2007/10/25 11:47:50

I use my air compressor. I did the test with the switch not installed in the brake line. I just screw the 1/8" threaded male sw conn into the air gun I use for blowing away dirt, etc. connect a ohmmeter or conductivity light to the common and N/C contacts and then adjust the pressure until the switch activates.
I found the wells RB402 brake switch will activate the N/C T/L contacts at about 38 to 40 psig, causing them to become open. I then connected the wires to the switch, 12v (pink) to common (center term), LT Grn to right term, Dk Grn to left term. I then presured to 40 psig, thereby killing power to the T/L switch. I figured the other terminal contacts for the brake lights should activate at the same pressure, but there was no change "no power to DK. Green wire to the brake lights", so I increased the pressure incremetally "about 5lbs at a time, didn't want to blow the diaphragm" until I reached 70 or 75 lbs, still no power to the dk grn wire. I moved all 3 wires to different terminals but, I never could get term 3 (left)to change status with the common or the N/C term which makes me believe the switch is faulty. I don't know how they calculate the pressure it takes to stop the vehicle but, I'm sure the equation includes mechanical aspects such as shoe or rotor size,etc. Anyway, I'll check it when I get the new switch and let you know the results.