Trailer Brake or Truck Problem?

[thomasmnile]

2005 Ram 3500 QC, Prodigy P3 brake controller (plug n play to truck harness) 2013 Jayco White Hawk 27DSRL (Dexter Axles/Electric Brakes)

Recently did a quick weekend to St. Augustine. Hooked up trailer doing brake check and manually activate trailer brakes, brake controller says trailer not connected. Checked 7 pin connector, went under trailer checked brake wiring no problems seen. Two 30 amp fuses at trailer positive cable battery connection, checked them, no problem (what are those fuses for anyway? They are on wiring between battery and a junction box of trailer frame, the tongue jack is separately fused). 90 minute trip up the road, flat terrain, good weather, truck brakes have plenty of whoa for truck and trailer so off we went. Got to campground and checked the truck's fuse for the trailer brake cicuit, it was blown. Replaced the fuse, hooked up the this morning and all is good. Brake check, manually activate the trailer brakes, no problem. Had the voltage output on the controller set to 8 volts. Brakes worked fine, typically drawing 5.9 volts when I hit the whoa pedal. Get off I-95 to head home apply the brakes and controller once again says trailer not connected. Haven't checked the fuse on the truck yet, but pretty sure I'm going to find it's blown.

I hope I provided enough info for the mechanical sleuths out there, but I'm at a loss for where to begin. In 3 years, I've had zero issues with the trailer brakes, and am inclined to think the problem is with the @#$%^& truck. The only thing I did to the trailer brakes prior to leaving was adjust them. Any thoughts, suggestions, quick cures? Thanks.

[BenK]

You have an intermittent short/open...toughest thing to find on electrical
systems...

[thomasmnile]

The plot thickens........Last night drove about 9 miles to a local restaurant in a thunderstorm (not especially heavy rainfall by Florida standards) and I suddenly notice the display on the P3 controller flashing a message stating 'Warning' Short to Battery No Brakes! In 8 years I have NEVER seen that message, with or without the trailer connected. All good info. but the trailer wasn't within 15 miles of the truck, let alone connected to the truck. Checked the electric trailer brake circuit in the truck fuse panel (the previously blown 30 amp)and it was fine. Matter of fact, when I reinserted the fuse then checked the brake controller, it had reset itself from the warning message and was displaying the normal home screen shown when the truck's ignition is on.

What in Gawd's name is going on? Inclined to take the truck to my mechanic, but would really like to have some idea of how to explain this weirdness so they aren't flying completely blind attempting to diagnose what may be happening.

[kaydeejay]

gkainz wrote:

CampingN.C. wrote:
Can't argue with the ol' Ohms Law !

Well... you can ... but resistance is futile. 🙂

Oh my, that is shocking!!!

[gkainz]

CampingN.C. wrote:
Can't argue with the ol' Ohms Law !

Well... you can ... but resistance is futile. 🙂

[CampingN_C_]

kaydeejay wrote:

Perrysburg Dodgeboy wrote:
Just a question for the electricians here. If a lose connection creates heat and it does would it not also increase the amps needed to power the circuit? Almost every campsite electrical box is worn out and some are so bad that it will even melt the cord. The ones like this all would trip the breaker. Heat is a sign of heavy draw right?

Don

Heat is the result of a high resistance connection, not an increase in current flow. In fact the reverse is true, current may be limited by that high resistance connection. A voltage drop across the connection will ALWAYS create heat, the amount will be a function of the current flow.

Many campsite receptacles are worn to the point that they make poor contact with the plug, aka high resistance, hence heat, resulting in melting the plug.
For example, if there was a 10 volt drop across the connection, drawing a 30amp current, then 300 watts of heat is going into that plug. I think you can imagine the result!!

Can't argue with the ol' Ohms Law !

[Perrysburg_Dodg]

kaydeejay wrote:
When did the 110volt side if your system come up??
Everything we have been talking about re your truck and trailer, especially brakes, is 12 volts.
I still say you have a chafed wire that is creating an intermittent short in your brake circuit.

The 110V was never an issue, I had made a comment about heat and used the campground power supply overheating my plug and tripping the circuit breakers.

The OP does not have a AC electrical problem. Sorry if my analogy confused anyone.

[BenK]

Careful...

Modern vehicles and their computers can be FRIED by some testers....especially those with a 9 volt battery inside it

Some Signal level voltage can be less than one volt...or be current sensing (milliamp)

Ben
Via smartphone phone...excuse my fat finger typos

[kaydeejay]

thomasmnile wrote:

kaydeejay wrote:
When did the 110volt side if your system come up??
Everything we have been talking about re your truck and trailer

Um, not quite. Go back 1 page. Since I had the truck in for the Takata recall, service writer asked if there was anything else. Told him about the trailer brake issue, and could they check the truck wiring and replace the fuse. They had the truck two days, wasn't done.

Once bitten, twice shy with this dealership. Took it there to run down a problem with the electrical system last September, dash volt meter was showing less than 12 volt output. Had it all day, scanned it they said could find nothing wrong and collected $105 for their 'effort'. Problem persisted, took it to the mechanic in Orlando that regularly services the truck, they found a problem with the cooling fan clutch and replaced it. No voltage output problem since,normal 14.2 v output. Don't pretend to understand that, but I do know the cooling fan now works, I'm not certain it ever has in the last couple of years.

What does any of this have to do with 110 volts?

[thomasmnile]

kaydeejay wrote:
When did the 110volt side if your system come up??
Everything we have been talking about re your truck and trailer

Um, not quite. Go back 1 page. Since I had the truck in for the Takata recall, service writer asked if there was anything else. Told him about the trailer brake issue, and could they check the truck wiring and replace the fuse. They had the truck two days, wasn't done.

Once bitten, twice shy with this dealership. Took it there to run down a problem with the electrical system last September, dash volt meter was showing less than 12 volt output. Had it all day, scanned it they said could find nothing wrong and collected $105 for their 'effort'. Problem persisted, took it to the mechanic in Orlando that regularly services the truck, they found a problem with the cooling fan clutch and replaced it. No voltage output problem since,normal 14.2 v output. Don't pretend to understand that, but I do know the cooling fan now works, I'm not certain it ever has in the last couple of years.

[kaydeejay]

thomasmnile wrote:
Well, my issue isn't with the 110v power, but I bought a good test light today and will begin the detective work starting with the truck, which I just got back from the dealer for the Takata 'airbags of death' recall repair. Both driver and passenger bags replaced.

When did the 110volt side if your system come up??
Everything we have been talking about re your truck and trailer, especially brakes, is 12 volts.
I still say you have a chafed wire that is creating an intermittent short in your brake circuit.

[thomasmnile]

45Ricochet wrote:
Now they have another recall on your new bags I heard. I wish they would just tell me which fuse to pull right about now and I'll take my chances with only the seat belts :E

Dealership invoice indicates replacement of passenger side airbag and 'interim' replacement of driver's side airbag. :h

Wonder if I should just drive wearing a Kevlar helmet and flak vest? I do agree given the sheer number of vehicles and the continuing problem with bag inflators fragmenting among replacement units, wouldn't it have been smarter for the Feds to simply order airbags on subject vehicles be disabled until Takata gets it right once and for all?

[45Ricochet]

Now they have another recall on your new bags I heard. I wish they would just tell me which fuse to pull right about now and I'll take my chances with only the seat belts :E

[thomasmnile]

Well, my issue isn't with the 110v power, but I bought a good test light today and will begin the detective work starting with the truck, which I just got back from the dealer for the Takata 'airbags of death' recall repair. Both driver and passenger bags replaced.

[kaydeejay]

Perrysburg Dodgeboy wrote:
Response not resonance LOL darn smart phone!

I figured ! :R