OT Trailer brakes

Got the dove tail out of the barn last night and hooked up the electric to the truck. Nothing. Worked on the contacts (corrosion) and finally got all the lights but no brakes. The send unit registers in the truck but can't figuare out how to test it. I've been all over the connector contacts again with no results. It's an older style 5 pin and really pushed for time to use the trailer. Anyone know how to test the brake sending unit ? Really could use some advice. Don't use the trailer that often but you need it , you need it. Thanks

Start off with the simple stuff first. Find which pin is the brakes. (female plug on truck) Put a test light or meter on that pin and press the brake pedal. (w/light or meter well grounded to truck chassis) Do you get current?

From my experiences, about 98% of trailer brake and/or lighting problems are ground issues.

Can't remember without looking but either the blue wire or the red wire feeds power to the controler.

The opposite wire should register voltage when the controler is activated.

If you have power coming out of the controler then jack up the trailer. Then supply power to the plug on the trailer with a battery charger or directly to a battery to the pin on the trailer that feeds the brakes.Remember to hook up a ground from the battery as well to the trailer.

If the brakes lock up using another battery then you have a wire issue or ground issue at the brake drums.

The brakes ground at the drum like to rust and loose contact.

Gary

Have you looked at the brakes themselves??. They are electro magnet actuated. rust on the magnets or the disk will prevent operation.

Speaking of trailer brakes, a friend of mine recently bought a 32 foot camper trailer at an auction in New Orleans and hauled it all the way up here to "uppa New Jork" behind his Diesel 1/2 ton GMC. He told me the brakes worked strictly off the brake light wiring and he has no brake controller in his truck. He said the brakes worked perfectly the whole trip. I admit I know practically nothing about the subject but I thought there had to be some kind of controller to coordinate the two braking systems?

Must be a controller with a pendulum in the camping trailer or something.

Has to have something to control the amount of force applied to the brakes.

Otherwise the brakes would lock up on the trailer with every little tap on the brakes.

Gary

MF Poor has pretty much summed up what you have to do.I do a fleet of twenty trailers every year for a friend of mine. Sometimes you think you have a ground but it is poor. I take a battery booster cable from the truck bumper or hitch to the trailer and the tale will be told. I usually use my grinder to make a small bare metal patch on the truck and on the trailer where it won't show. Lights will do the weirdest things if the ground isn't right.Both left and right will flash when you signal one way or the other, clearance lights will flash with the signals, brake lights will be dim..just weird stuff because th ground isn't right. Find that brake pin and ground the system.
You can always tell if trailer brakes have been working..3 ways...the face of the drum is shiny from the magnet rubbing it, the drum surface is shiny from the shoes rubbing them and the magnet will not light up your test light with the brake applied. If the magnet looks bluish it is likely cooked.Lube all moving parts in the brake, activating arm, shoe pivots, adjusters etc. Re grounds, I sometimes attach a wire from component to component on the trailer to ensure ground.For example I will metal screw a piece of wire to the inner fender and then to the frame of the trailer, this guarantees a ground even when rust breaks the original ground weld.

All the ideas I've read so far are good ones.

One other thought, comes from experience helping a friend get a new to him horse trailer ready to go. He tended to some other things while I repacked his bearings. Got all set to check things out and NO brakes! I (gently as I could) suggested that he dial the output on his controller up above zero and see how they worked.

Seen it happen enough it seemed worth bringing up.

P55, Your center pin should be your brake wire. The controller gets power from the "HOT" side of the brake light switch with the brake pedal depressed (No, we"re not talking trash about the switch"s ugly sister!) and usually comes ot of the center pin. I"m more familar w/the 7 pin units, but as others have said, try a known good battery and good hot and ground wires to the brake wires . Jack up the wheels one at a time and try spinning the wheel. They should lock up. Let us know what you find.

does it have a disconnect cable? If my camper comes disconnected the cable pulls out and locks up the brakes. I found out a couple weeks ago that it works. Pulled it apart hooking up the safety chains.