Can I bench test a stop light switch that is an inline switch activated by the pressure from a hydraulic cylinder-? I can feel the plunger/shuttle go in and out, when removed, by pushing a nail through the hole where the fluid activates the switch. If I push the plunger/shuttle in and test across the two electrical contacts, should I get a reading on my continuity meter which would show that the contact was closed thus completing the circuit-? I have tried doing this but I get no reading whatsoever-? I have also tried placing this and another switch I bought in a 12V circuit to see if this would activate a 12V test light when the plunger is activated. It did not. I would think that by pushing in the plunger-shuttle by had it would simulate the pressure from hydraulic fluid and indicate the switch closed and completed the circuit-? Or, do I just have a couple of bad switches-? This problem is driving me nuts. My guys at the parts store think I don't know what I'm doing by buying all these stop light switches. I'm beginning to agree.

Your on the right track with your bench test but it looks like your switches are bad......take your meter to the parts store with you and show them...test every switch they got untill you find one that works.

Doc here,

IF you tested the First switch, IT may be dead..(the reason you were drawn to the repair..) Toss that one in the trash.

Take ANY of the new switches, and your test lamp, or meter, go to the gas station, hook either the test lamp ACROSS the terminals (if the lamp has it's own battery's) OR your Meter set for continuity / Beep..

Insert the air nozzle into the switch orifice and give it a blast..The lamp should light, Or the the meter register/beep..IF not the switch (s) is / are Defective..(and a bad batch from the same store would not surprise me).

If it does light, you need to inspect the differential valve or proportioning valve on the line from the master cylinder..



Also remember: Front pressure will Be slightly LOWER than rear pressure..which may be the problem..

Doc

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