Update on Trailer vs Prodigy Issue from below - Diesel Forum

AaronSEIA · 09-12-2009, 06:07 PM

So... I cut all the wires off the magnets leaving myself enough to re-wire. I've got approx 12v from the controler at the truck plug, same at the end of the trailer pigtail in the junction box. I've got approx 12v if I unhook the ground wires at the brakes and use my multi meter between the wire and the frame. Brakes are grounded to the frame of the trailer, and trailer is grounded to the truck through the 7 pin, not just the ball. When wife manually applies the slide bar Prodigy still says nc, but...I can hear the brake magnets buzzing. Is it possible I have 4 bad magnets? Anyone know how to test them? I use the ohm funtion on my tester and came up with 3.5 if I remember right. They are 10" Dexter brakes. Polished up all the connections and no difference.
AaronSEIA

94_turbo · 09-12-2009, 06:37 PM

i wonder, if you have a wire thats cut somewhere on the truck. not comp thru, just enough to cut the AMPS down, and aint applying the magnets strong?? also--take a batt back there, and apply full voltage to the mags. you shouldnt be able to pull a good putty knife off with a tank---

**Scottb NY** · 09-12-2009, 06:50 PM

I would take and run a wire outside the harness and test it. It sounds like the brake lead is corroded someplace. Voltage is only 1 component needed to allow the brakes to work. Current is the other one and a corroded wire will give you 12volts but will not have enough current to do the work. You could take a headlight bulb back to where you cut the leads and see if the controller will light it when manually applied.

the formula is E=IxR or Vlotage = current x resistance.

Quote:

Originally Posted by AaronSEIA

So... I cut all the wires off the magnets leaving myself enough to re-wire. I've got approx 12v from the controler at the truck plug, same at the end of the trailer pigtail in the junction box. I've got approx 12v if I unhook the ground wires at the brakes and use my multi meter between the wire and the frame. Brakes are grounded to the frame of the trailer, and trailer is grounded to the truck through the 7 pin, not just the ball. When wife manually applies the slide bar Prodigy still says nc, but...I can hear the brake magnets buzzing. Is it possible I have 4 bad magnets? Anyone know how to test them? I use the ohm funtion on my tester and came up with 3.5 if I remember right. They are 10" Dexter brakes. Polished up all the connections and no difference.
AaronSEIA

OT · 09-12-2009, 07:19 PM

Aaron..I have to ask...did you check each wheel (axle jacked up) eng. running & t. plugged in..applying manual (slider) brake..did each wheel stop? If not done, then.. If u got 12V reading at magnets..reading thru the 2 wires from magnet..should be enough V to activate good magnet. Scott may have point on amps, cause Im not sure? But....

Test is simple, but gotta take wheel/drum off. Need helper or something to hold brake pedal down..engine running/t.plugged in..stick at least a 10" crescent wrench to magnet..Does magnet hold wrench? Basic test at best, but if magnet dosent hold wrench, suspect bad magnet. Good luck!

btw..just following along cause I'll soon be upgrading my old voyager to prodigy.

**artkelly** · 09-12-2009, 07:58 PM

Here's an older thread on the subject of T/S'ing trailer brakes. Trailer Brake Adjustment

As I said there, an ammeter is a big help. Dexter brake magnets draw around 3 amps each at 12 VDC.

I can send you a trailer-brake manual if you PM me. (It's 9-1/2 magabytes.)

I checked the link to the clip-on ammeter that was in the older thread, but it no longer works. Camping World used to carry one made by Tekonsha, but it's no longer in their catalog. It's a shame they're hard to find--they are only $10-15 and completely adequate for T/S'ing brakes.

Sears has this one Craftsman Digital Clamp-On Ammeter on sale right now for $50. The lowest DC amps scale is 40, so you should easily determine if a magnet is working or not. The good thing about clamp-ons is that a brief short probably won't harm the meter.

Tekonsha sells test gear, but it looks expensive and they don't list their prices

. See item No 6565 at http://www.tekonsha.com .

As long as there isn't a short, you could use a VOM if it's rated at 3 amps X Number of axles. Put a 12 VDC lamp in series with the meter the first time. If it lights brightly, you probably have a short.

tinkerr · 09-12-2009, 08:14 PM

I don"t if this applies, but my prodigy would read nc, meaning no connection. the brakes on the trailer were not happy being grounded to the frame of the trailer. I ran a ground wire from the harness to each brake and problem solved.

Rick M · 09-13-2009, 01:24 PM

Quote:

Originally Posted by tinkerr

I don"t if this applies, but my prodigy would read nc, meaning no connection. the brakes on the trailer were not happy being grounded to the frame of the trailer. I ran a ground wire from the harness to each brake and problem solved.

That is what I have read about electric brakes, either direct wiring to the ground wire or both, but not through the frame only. One article I read even suggested equal lengths of hot wire to all brakes instead of the typical short wire to the brake on the side the main wiring is strung down with a long wire over or through the axle to the far side. Went on to recommend no quick connect taps but rather full crimp or better yet solder all connections. This is what I will do when I re-rig my brake and light circuits, strip, solder, multiple coats of liquid tape. A bit time consuming to do, but so much less stress when the lights consistently work as they should and the brakes give all the stopping power they are designed to.

**artkelly** · 09-13-2009, 08:44 PM

Must be FM.

**artkelly** · 09-13-2009, 09:00 PM

Brake magnets should be parallel wired for optimum system performance.

Also never use the trailer frame or brake cluster backing plate for the (-) brake negative current return. The negative (-) wire must be brought all the way through the trailer plug back to the tow vehicle negative for optimum system performance. Loose connections at the trailer plug, wire taps, and voltage drop from wiring that is too small can radically affect your electric brake system performance. Installation tip - Never use pinch type wire taps for electric brake wiring. They may be adequate for trailer lighting systems, but the high current draw for electric brakes require compression (crimpon) connectors or soldered wire taps for best performance.

From: ELECTRIC * HYDRAULIC * DISC TRAILER BRAKING SYSTEMS Contains information on electric AND hydraulic systems. Seems like a pretty good source of material.

Art

Rick M · 09-14-2009, 07:49 AM

Artkelly,

I had come across that drawing awhile back, but it did not make a lot of sense to me since it is showing a single string of magnets and most axles I have looked at have two magnets. Is this drawing and the article suggesting that one wire a tandem axle trailer in such a way that the first magnet in the drawing would be the left front, then the left rear, then the right rear, and lastly the right front? Or I guess it could be showing left front with the pair of wires over to the right front then to the right rear and then to the left rear. That drawing is clear electrically just not to the typical trailer. Dummy me.

olddieseldude · 09-14-2009, 10:30 AM

Quote:

Originally Posted by Rick M

Artkelly,

I had come across that drawing awhile back, but it did not make a lot of sense to me since it is showing a single string of magnets and most axles I have looked at have two magnets. Is this drawing and the article suggesting that one wire a tandem axle trailer in such a way that the first magnet in the drawing would be the left front, then the left rear, then the right rear, and lastly the right front? Or I guess it could be showing left front with the pair of wires over to the right front then to the right rear and then to the left rear. That drawing is clear electrically just not to the typical trailer. Dummy me.

That drawing is an electrical schematic. It is not a literal wiring diagram of a trailer. It is telling us that regardless of where we route the wires, each brake's magnet needs to attach to the negative and positive wires coming from the tow vehicle independently. No brake's magnet should depend on a circuit passing through another brake's magnet for either it's power or ground. This allows one wheel's brake magnet to short out (open circuit) without affecting the braking function of any other wheel.

(Edited: reread post)

A trailer brake install video...