A rat chewed off one of my brake wires. I repaired it and wondered if any other places were chewed. After pondering it for a while, I turned off the converter, unplugged the breakaway switch and hallelujah the Tri Metric indicated 12 amps of draw. Now this will not test the plug or guarantee that some other wire had some teeth marks, but it is a quick and easy way to check.

I've done the same myself but I never got to 12A.

3 amps per brake is normal maximum draw for electric brakes. At 12 amps, I'm figuring you've got 4 brakes.

I used to get out a compass and have DW hit the brake peddle. When I held the compass near the brake, the needle would swing. If it didn't, I knew I had found a bad brake. I do hope you found all the chewed wires. I hate that. Matt

*** The compass tickled me. Great abstract analysis !!!

joebedford wrote:I've done the same myself but I never got to 12A. The bath fan and some other parasite loads were still on. But close enough for me.

Found a new way to test brake wiring and magnets

11 Replies

joebedford
Nomad III
Sep 01, 2019
The integrated brake controller in my Silverado has a pressure sensor on the master cylinder to tell how hard I'm pressing the brake pedal. Unfortunately these things can fail (mine did) and the geniuses at GM decided that the brake controller shouldn't output anything if it doesn't know how hard I'm pressing - INCLUDING THE MANUAL CONTROL. So I'm rolling down the highway with a 20000lb toy hauler on the back with no brakes. What were they thinking? They did put a 'helpful' message on the DIC saying something like 'Check the brake system'.
rjsurfer
Explorer
Sep 01, 2019
Rcman46, thanks for the diag info.

Ron W.
Matt_Colie
Explorer II
Aug 31, 2019
My coach is way too old for that.
The brake control Kelsey Hayes and is Teed into the rear brakes and is activated by the brake pressure. I like it because it actually tracks the applied brake pressure.

Maybe I will look for something newer when the flints where out.
-OOPs wrong technology.

Matt
RCMAN46
Explorer
Aug 31, 2019
This is how to get current reading from a P3 controller.
rjsurfer
Explorer
Aug 31, 2019
RCMAN46 wrote:
That is what I love about my Prodigy P3. It has a diagnostic function that I use every morning before I start a trip.

With four brakes I have found it is 1 amp per volt applied. My max setting when I use the manual lever is 7.5 volts thus I should read about 7.5 amps with full lever travel for my setting.

How do you initiate this test, or is done automatically on power up?

Ron W.
RCMAN46
Explorer
Aug 31, 2019
That is what I love about my Prodigy P3. It has a diagnostic function that I use every morning before I start a trip.

With four brakes I have found it is 1 amp per volt applied. My max setting when I use the manual lever is 7.5 volts thus I should read about 7.5 amps with full lever travel for my setting.
joshuajim
Explorer II
Aug 31, 2019
joebedford wrote:
I've done the same myself but I never got to 12A.

The bath fan and some other parasite loads were still on. But close enough for me.
MEXICOWANDERER
Explorer
Aug 31, 2019
*** The compass tickled me. Great abstract analysis !!!
Matt_Colie
Explorer II
Aug 31, 2019
I used to get out a compass and have DW hit the brake peddle. When I held the compass near the brake, the needle would swing. If it didn't, I knew I had found a bad brake.

I do hope you found all the chewed wires. I hate that.

Matt
DFord
Explorer
Aug 31, 2019
3 amps per brake is normal maximum draw for electric brakes. At 12 amps, I'm figuring you've got 4 brakes.