Weak Braking w/ Tekonsha P3

tom496 wrote:

DiskDoctr wrote:
Tip: Using a 12v battery and a couple pieces of wire with the ends bare can be used to test your trailer wiring directly, using your trailer's connector, sans vehicle and controller.

Can anyone direct me to instructions for this procedure?

I'll be reviewing this thread for other possibilities, including doing the mechanical adjustments on each wheel as has been suggested. However, as I mentioned earlier, last fall I could lock up the wheels with the manual lever and now the lever hardly slows the rig. It's hard to imagine that the mechanical adjustments are the problem.

Any other suggestions appreciated. Thanks.

Pretty straight forward.

1. Disconnect your trailer pigtail from your TV

2. Get a diagram for your connector. Remember, the trailer end is OPPOSITE of the TV end ;)

3. Use 12V battery and connect a piece of wire to connect from the Ground (-) of battery to the ground pin of your wire harness. I use stranded wire and find that stripping a little over twice the length I need, then folding the stripped area in half allows a nice rounded profile when inserting the wire, provides some good friction due to the shape of the wire, and keeps the ends of the strands out of the connector, preventing the wires from getting stuck in the connector.

4. Use a piece of wire (I have one with a momentary switch in the middle, which helps) and connect it in a similar manner to one of the light pins, such as running lights (which are easy to see from the front of the trailer). Touch the other end of that wire to the battery Positive (+) terminal. DO NOT FASTEN THE WIRE TO THE BATTERY (+) TERMINAL. Far toooo easy to short it out that way. Just touch it, it won't shock you. Make sure the lights come on and the pin layout matches your diagram.

5. Here's where I take a few moments to draw a diagram of the connector and pinout, move the (+) wire to each of the other connectors (except ground, which is *sometimes* on the middle pin, check your diagram) and verify pinout and proper operation of lights, turn signals, etc. Tip: if you place something white or reflective about a foot behind your tail lights, you should be able to see the reflection when they are on.

I also make notes on this sheet as I go. Any weak or intermittent operation is noted. Remember, we are also looking for a weak ground.

6. I jack and block up one side of the trailer. Have a buddy spin one of the wheels and touch the Brake pin wire to the (+). Keep in mind, you are only using ONE hot wire in addition to the ground and moving it around. Be sure not to touch them together.

The wheel should stop instantly and firmly. Repeat for the second axle on that side. For each, try to force the wheel to turn. It shouldn't. Also make sure they spin freely with no dragging or gritty sounds when the power is not applied.

Repeat for other side.


Now some items.

1. If lights are weak or don't function properly, you will need to test your ground line. I ALWAYS run a ground through the plug pin. It has a spot for it and is marked.

You can have a buddy help. Attach ground terminal to ground pin (hold it in place). Use your meter to check DC voltage between terminals on battery, write that number down. Do not connect the positive wire, instead, use your meter to touch one end to a pin on the connector (lights, brakes, whatever) and the other end of your meter to the battery +. Write this number next to the pin you used on your diagram. Repeat for each pin.

You may notice a small drop in voltage due to lights and other resistance. Not a big deal as long as it is small. You ARE looking for a DIFFERENCE in this drop on different pins that is more than a few tenths of a volt. This will help you isolate a bad circuit.

**

That is the BIG version. Proceed until you find the problem ;)

But FIRST, I'd suggest getting some good electrical cleaner and a fingernail file and thoroughly CLEAN the TV end of the connector (each pin, be very GENTLE with only a few strokes of the file, liberal with the spray cleaner), and do the same with the trailer end.

The connectors should be SHINY. Dull looking brass may look clean, but doesn't make good electrical contact. You are looking not to polish them to a high gloss, rather break through the dull coating and let the electrical connector do the polishing.

You can also pull the cover off your trailer connector if you wish to inspect the connectors. A pin with a problem circuit will often have green or white corrosion on the pin or the connector.

The connectors are often held on by a small screw near the keyed section, sometimes on the face, and often with a clamp style connector at the back of the connector that clamps the connector opening to the whole cable (strain relief).

If you do this carefully, you should be able to slide the outside cover further onto the cable, exposing the wiring connections inside the plug end for inspection. About an inch or two should be enough. If you decide to do this part, do yourself a favor and spray the connectors with electrical cleaner, let them dry, then add a dab of dielectric grease to each before replacing the cover (remember, it is keyed to fit only one way).

Dielectric grease is NOT a conductor. It is more of an anti-corrosion protector. Anti-oxidant, specifically, but more folks are familiar with the term corrosion ;)

Back to brakes- mechanical.

If you remove the wheel and outer hub, inspect for any major rust or obviously compromised/broken wires, parts, etc.

You should be able to move to long "crooked L-shaped lever" attached to the brakes DOWNWARD. Don't go too far, but verify that each moves with minimal, primarily spring-type resistance and that the brake pads move outward. They often only move a small distance.

The pads will likely not move concentrically and only one may move. That's fine. Just help them back to center when you release the lever. They push against the inside of the hub and center themselves.

Important note: The electric brakes will NOT WORK with the hub off. You surely understand this now that you know the magnet grabs the hub, the hub rotates forward, the brake arm is pulled downwards, the pads are pushed outwards against the inside of the drum/hub.

Also take a moment to see that the crooked L-shaped lever is FACING FORWARDS on every assembly. That's why they are marked with Left and Right ;)

You can take two hubs off at the same time and compare them. Check for broken springs, missing brake liner on the pads, etc.

Yes, the magnets fit loosely on their center pin.

Hope this helps.

The theory about the settings having been turned down was correct, but that apparently occurred between the time I took the readings in my original post and when I took the second set of readings that I posted. When I turn the power setting back to the maximum (13.3), I get the same readings on the P3 that are in my original post.

I now have power to all four wheels, but I now think the lack of current with the compass test on one of the wheels was an anomaly or intermittent. I think I'm basically where I started out, but at least getting educated.

DiskDoctr wrote:
Tip: Using a 12v battery and a couple pieces of wire with the ends bare can be used to test your trailer wiring directly, using your trailer's connector, sans vehicle and controller.

Can anyone direct me to instructions for this procedure?

I'll be reviewing this thread for other possibilities, including doing the mechanical adjustments on each wheel as has been suggested. However, as I mentioned earlier, last fall I could lock up the wheels with the manual lever and now the lever hardly slows the rig. It's hard to imagine that the mechanical adjustments are the problem.

Any other suggestions appreciated. Thanks.

I made this observation last night --

Tom496 wrote:
I also put my multimeter on the cut ends of the trailer-side leads to the magnet. With the controller manual lever pushed all the way to the left, I read 4.5 volts. (The reading on the Tekonsha was 6.0).

I didn't recall previously seeing the setting at 6. Then Longtrace and bartlettj both suggested that the P3 may have had the power level turned down inadvertently. I think that may be what is going on. In reviewing the Tekonsha instructions, I noticed that the procedure for adjusting the power level suggests starting on level 6, and then adjusting up or down as needed. I now think that 6 is the default and my unit somehow got reset to the default. I guess I didn't suspect this possibility earlier because it had never happened in the 4-5 years I've owned it, including when I re-installed it in a second TV.

This does not explain the compass not picking up current on one of the wheels, but I plan to clean up the points of contact between the magnet and actuator arm, as outlined here. An intermittent short there might explain why both the magnet and the wires energizing it passed my tests.

I will report back. Thanks again for all the excellent advice and suggestions.

bartlettj wrote:
There are two adjustments on the P3- boost and braking power(voltage). They are not the same. Did you or someone turn the braking power down? Parked and applying the brake you should not get much voltage out, only what the boost setting tells it based on the brake light. Actually moving and stopping the unit will apply more voltage based on how hard you are braking the vehicle.

I have the Tekonsha Prodigy. The proportional braking does work as you describe, but when applying manual lever, it maxes output up to the dial setting.

When adjusting, I move about 5-7 mph with one wheel on the gravel on side of road on level section. Apply lever to max (boost is 0). I adjust until I get the desired setting. On lighter flatbed trailers, I set it to the tires on the gravel side just skid, then back off a touch.

On the camper, I drift on level, apply lever and set dial where I feel aggressive and strong pull, but not violent jerking. Then I use B3 (max boost) to be more aggressive on the proportional application of trailer brakes.

Not sure if the P3 is the same?

FYI. I used the manual override when one of my flat trailer brakes malfunctioned and it kept reading 'SH' (short). Forced other brakes to work. Found out later the wire on one magnet broke off and was occasionally shorting inside the drum. Hence my earlier comments about the wires on the magnet ;)

Hope this helps.

There are two adjustments on the P3- boost and braking power(voltage). They are not the same. Did you or someone turn the braking power down? Parked and applying the brake you should not get much voltage out, only what the boost setting tells it based on the brake light. Actually moving and stopping the unit will apply more voltage based on how hard you are braking the vehicle.

The way I adjust my P3 is to first make sure the trailer brakes are adjusted properly, then turn off the boost function and adjust the voltage until I get enough braking power so that it stops well and doesn't lurch, but I can still feel that I apply more pedal with the trailer than without. Then I turn the boost function up until for most stopping situations I can't feel the trailer.

tom496 wrote:
I am just getting back to this problem after a few days. Thanks for the comments I received in the meantime.

When I placed a compass next to each wheel and engaged the controller, the needle turned a full 90 degrees on three of the wheels and didn't budge on the driver's side rear wheel.

No magnetic field = no braking - on that wheel. But total failure of one brake should not prevent the other three from having enough force to lock the wheel. Total brake performance will be less, though.

I inspected the wires and saw nothing suspect. I pulled the wheel and inspected the magnet and, although grimy inside the drum, there was no grease or any heavy rust anywhere.

I removed the magnet by cutting the wires. Here's what it looks like:

Looks fine - but that doesn't mean much. :)

I performed the tests recommended here: http://www.etrailer.com/faq-testing-trailer-brake-magnets-for-proper-function.aspx using a 12v battery and multimeter. I was outside the specs:
My reading: 2.9 amps
Recommended reading: 3.2-4.0 Max amps at 12-13 volts
Resistance - my reading: 4.7 ohms
Recommended reading: 3.0-3.8 ohms

It is outside the spec. - but just. The compass should still swing around with that much current flowing. Therefore, the problem must be lack of supply power to that magnet.

I also put my multimeter on the cut ends of the trailer-side leads to the magnet. With the controller manual lever pushed all the way to the left, I read 4.5 volts. (The reading on the Tekonsha was 6.0).

That is not a very trustworthy measurement. Your meter has will read fine if there is a connection so poor that only 1/4 of one 28 AWG strand in the cable is still connected - but the brake magnet won't have enough power to do any work. I'm also puzzled because in an earlier post you said the P3 reported 12.1 V with the manual lever fully applied.

The compass test clearly showed that one magnet was not doing it's job. That should be fixed. However, based on the P3 readings you posted earlier, I suspect there is more problems with your brake system than just the one non-contributing magnet. I would want to check the mechanical parts of all the hubs.

Also, I would expect the P3 to generate 13.6 V - or at least the 12.1 it did before - when the manual lever is fully applied. Since I have never used one, I can't advise you much, but it sounds to me like maybe there is a max-power adjustment that is "turned down".

Regarding further tests... I would measure the voltage at the magnet connection, comparing magnet-connected and magnet-disconnected - both while applying the manual lever on the P3. It should be a little less than when the magnet is not connected. If it is a lot less, then there is wiring troubles - probably corroded or damaged connections. You could also use the compass, though if there is current though the magnet there will be a magnetic field.

I would also check the ground connection through the trailer-to-tow-vehicle connector. If it's bad, the ball and coupler will often supply a ground path - but not a very dependable one.

RCMan, these are the readings from the P3's diagnostic mode with one of the magnets disconnected:

OUTPUT VOLTAGE
No braking -- 0 V
Brake pedal fully depressed – 1.4 V
Manual lever pushed fully to the left – 6.0 V

OUTPUT CURRENT
No braking -- 0 A
Brake pedal fully depressed -- 0.5 A
Manual lever pushed fully to the left – 3.5 A

I'm not whether this was what you were saying I should measure. If not, where were you suggesting I take that current reading? Thanks.

Spike, thanks for those links. That's nice looking rewiring you did on your trailers.

tom496 wrote:
I am just getting back to this problem after a few days. Thanks for the comments I received in the meantime.

When I placed a compass next to each wheel and engaged the controller, the needle turned a full 90 degrees on three of the wheels and didn't budge on the driver's side rear wheel. I inspected the wires and saw nothing suspect. I pulled the wheel and inspected the magnet and, although grimy inside the drum, there was no grease or any heavy rust anywhere.

I removed the magnet by cutting the wires. Here's what it looks like:


I performed the tests recommended here: http://www.etrailer.com/faq-testing-trailer-brake-magnets-for-proper-function.aspx using a 12v battery and multimeter. I was outside the specs:
My reading: 2.9 amps
Recommended reading: 3.2-4.0 Max amps at 12-13 volts
Resistance - my reading: 4.7 ohms
Recommended reading: 3.0-3.8 ohms

I also put my multimeter on the cut ends of the trailer-side leads to the magnet. With the controller manual lever pushed all the way to the left, I read 4.5 volts. (The reading on the Tekonsha was 6.0).

I'm not sure where to go from here and would be grateful for additional comments or advice. Is it likely that replacing that magnet will solve my problem? Does the 4.5 volt reading from the wires to the trailer suggest any additional tests that I should perform? Thanks in advance.

When you push the controller all the way with 6.0volts on controller what is the current with the one magnet disconnected?
Due to the PWD square wave output from the controller most volt meters will not be the same as what the controller reads.

.

To view instructions on brake adjustments to testing magnets, surf page 13 - 16 within - Click Here -

Note: Page 20 - 22 shows how to measure current flow in the Magnets.

If replacing brake wiring, I'd recommend removing the factory linear wiring and install much better STAR design. For more details, surf: - Click Here - - Click Here - - Click Here - - Click Here -

If wondering... I installed STAR wiring (outside the axle using thick 10 gauge wiring) under each of my Utility, RV/TT and boat trailers and their BEFORE and AFTER results are amazing. NO more weak brakes and their behaviour is now predictable. IMO, STAR design wiring inside plastic PEX piping and plastic loom (which doesn't rust) should be factory minimum build.

Hope this helps.

I am just getting back to this problem after a few days. Thanks for the comments I received in the meantime.

When I placed a compass next to each wheel and engaged the controller, the needle turned a full 90 degrees on three of the wheels and didn't budge on the driver's side rear wheel. I inspected the wires and saw nothing suspect. I pulled the wheel and inspected the magnet and, although grimy inside the drum, there was no grease or any heavy rust anywhere.

I removed the magnet by cutting the wires. Here's what it looks like:


I performed the tests recommended here: http://www.etrailer.com/faq-testing-trailer-brake-magnets-for-proper-function.aspx using a 12v battery and multimeter. I was outside the specs:
My reading: 2.9 amps
Recommended reading: 3.2-4.0 Max amps at 12-13 volts
Resistance - my reading: 4.7 ohms
Recommended reading: 3.0-3.8 ohms

I also put my multimeter on the cut ends of the trailer-side leads to the magnet. With the controller manual lever pushed all the way to the left, I read 4.5 volts. (The reading on the Tekonsha was 6.0).

I'm not sure where to go from here and would be grateful for additional comments or advice. Is it likely that replacing that magnet will solve my problem? Does the 4.5 volt reading from the wires to the trailer suggest any additional tests that I should perform? Thanks in advance.