Brake Warning Switch Again

-
mydart270

mydart270

myDart270
Joined
Mar 18, 2014
Messages
190
Reaction score
7
Location
Brattleboro, VT
Hi and Hello:

Hate to keep asking but this subject but learned a lot about these safety devices. My questions deal with the "gold" brass distribution and warning switch (its not a proportional valve!!!) located on the frame, drivers side. My car is a 1968 Dodge Dart 270 drum brakes all 4 wheels, SL-6.

(a) what ohms reading do you measure from the "black" threaded stem to frame ground? I have (2) "original " BWS and they measure "infinite" resistance, thus brake light is OFF,

(b) i installed a new BWS from InLine Tube (long story, don't ask why I purchased) and I measure about 6 M ohms...dah!!!!. Currently Brake Light is OFF. Pedal pressure is firm (best it has ever been, road test today) after vacuum bleeding.

Curious about this. The forum conversations say these aftermarket BWSs are junk from InLine. I cant return because all ready used and a pain to uninstall and re-bleed brakes with new installed "original" BWS. I called InLine and they are clueless with my question and really no help!!!!! Will call Right Stuff today, they have awesome tech help and articles.

Maybe reposition BWS to "middle" position will make a higher ohms reading?? I could remove existing "black" switch and replace with "original" but again a real pain. Brake light is ON when I ground the "boot" lead removed from BWS so electrical is OK.

Sorry for long verbiage. Just curious. Thx for reading. Any thoughts, comments, recommendations appreciated for above curiosity and findings.

Thx guys...BTW...i purchased MityVac Bleeder MV8000 (don't buy junk but usable), purchased TGR Brake HT-16000 flaring tool for perfect flares, reformed brake lines w/ marginal flares and leaks (another don't ask), and now ready to go I hope. Your input greatly appreciated for all my new tools !!!!!!!

Happy Mopar..Enjoy Fall..

.
 
I would not worry about it it can just be the meter is measuring the actual brake fluid. 6Meg is almost open in your situation.
 
halifaxhops said:
I would not worry about it it can just be the meter is measuring the actual brake fluid. 6Meg is almost open in your situation.
Click to expand...
Thx...that's what I thought. If the shuttle valve in the BWS is centered, its an OPEN ckt for sure. Maybe aftermarket BWS do not center properly but positioned enough to cause an OPEN ckt to brake lamp, thus measuring continuity thru brake fluid. After market BWS supposed to be centered according to InLine.
 
"It should" be infinite, but...........were you maybe touching the probes with your fingers? Body resistance. Even only 1K ohms is not going to light that light bulb and won't even cause much "parasitic draw" on the battery

Ohms law............I= E/R

Pick it out of the air a 194 bulb is shown as .27A at 14V. Solving for resistance (which changes) gives us about 52 ohms for the bulb. The "leak" R of the bulb and the switch are in series.

So the other "I picked out of the air" the 1K example added to the 52 ohms of the bulb the parasitic draw if you have 1052 across 12.6V is I= 12.6/ 1052 comes out .012A or 12 mA. That might run the battery down "in a month."
 
halifaxhops said:
I would not worry about it it can just be the meter is measuring the actual brake fluid. 6Meg is almost open in your situation
Click to expand...
It would only draw 0.0021 mA (0.0000021A)


You could do a test.

Measure one of our old ones, see what the resistance is between post and body of switch. Then push in the button and see what the resistance is.

If there is no change than the spool does the grounding, but i suspect the button makes or brakes a switch contact and has no connection to brake fluid.

The spool is self centering, but it could be less than free to move being new.
 
Last edited:
Also the switch may be "seeping" brake fluid and brake fluid may be somewhat conductive, don't know
 
67Dart273 said:
I come up with 0.0000021 for 6M ohms but it's still a tiny amount LOL
Click to expand...
My bad, i did 1,000,000 ohms corrected above.

Just measured brake fluid, definitely in the meg ohm range.

Salt water in the kilo ohm range.
 
Last edited:
You must log in or register to reply here.
-

Back
Top