M35a2 Brake Light question

[Bigsbetter]

My brake lights increase in brightness the harder you push on the brake pedal. The voltage going into the pressure switch which is on the hydraulic side is 24-25 volts. Coming out of the pressure switch can range from 5 volts to 24 volts(depending how hard you press the pedal) and this is what the bulbs see. Is this normal? I would rather my brake lights come on FULLY bright like a normal car even if I’m just lightly applying brakes.

 

[Gypsyman]

It sounds like someone has installed a pressure sender like you would use on a gauge instead of a pressure switch (simple on/off).

 

[williamh]

It sounds like someone has installed a pressure sender like you would use on a gauge instead of a pressure switch (simple on/off).

I would replace the sender , it should be an on and off switch , lower voltages could cause a higher amperage issue ( lower volts=higher amps) and cause premature lamp failure. Plus I’ve never heard of a reostat (variable output switch for break lights )? I’m only pushing on the breaks s little do I only need a little red light. Not like laying on them and now it’s twice as bright. ( burning out bulbs ?). My 2 c.

 

[Bigsbetter]

It sounds like someone has installed a pressure sender like you would use on a gauge instead of a pressure switch (simple on/off).

That’s what I need to know. I’m a mechanic by trade, BUT I don’t know how these machines operate. Is it supposed to be a on/off switch and not a gradual pressure switch??

I would replace the sender , it should be an on and off switch , lower voltages could cause a higher amperage issue ( lower volts=higher amps) and cause premature lamp failure. Plus I’ve never heard of a reostat (variable output switch for break lights )? I’m only pushing on the breaks s little do I only need a little red light. Not like laying on them and now it’s twice as bright. ( burning out bulbs ?). My 2 c.

thanks guys, I didn’t think it seemed correct. I’ll look for the right switch and replace it.

 

[HDN]

It sounds like someone has installed a pressure sender like you would use on a gauge instead of a pressure switch (simple on/off).

They're interchangeable?

 

[KN6KXR]

It's busted. Save some money and don't replace the stock one. Get an air side switch and convert it to that. I think Big Mike has them. I replaced my busted hydraulic one and it failed again a few hundred miles later. Waste of money. Air side switch has worked fine since.

 

[cattlerepairman]

It's busted. Save some money and don't replace the stock one. Get an air side switch and convert it to that. I think Big Mike has them. I replaced my busted hydraulic one and it failed again a few hundred miles later. Waste of money. Air side switch has worked fine since.

PLEASE go and do as @KN6KXR recommends. It eliminates the hydraulically operated switch as a failure point for the single circuit hydraulic brakes as well. The OEM switches can break the bakelite/composite center and leak brake fluid.
Converting to an air pressure switch on the air side is not complicated and not much more expensive than a replacement hydraulic switch (the correct one; not the ones from NAPA for cars that cannot handle the pressure in a Deuce hydraulic system).

More info: https://www.steelsoldiers.com/threads/updated-brake-switch.69170/