I'm in the middle of setting up my '90 F250 w/ an electric brake control. It doesn't have any factory provisions for trailer wiring so I've been doing it all from scratch. I ran a full harness from the 7 pin connector straight up the chassis into the engine bay. Tonight I got the main wires tied into the system so now when I step on the brake pedal the red LED glows on the brake controller.

I jammed a windshield squeegee into the brake pedal so that I could measure the voltage at the pin on the 7 way. I only got about 3 volts. My question is- is this normal? I'll get a helper tomorrow and measure the voltage with the 'emergency stop' level pushed all of the way over to see if I get a full 12V but I have no idea of how much voltage should be back there when just the brake pedal is applied.

 

Depending what brake controller you have, 3v is all you will get. Alot of controllers out there have a pendulum inside to swing forward(when moving and brakes applied) and this will send more voltage to the trailer the farther the pendulum swings. It is really a STUPID idea. If yo hit and hold the override, it will send the full 12v to the trailer

I really like brake controllers that read the trucks brake pressure then sends equivalent voltage to the trailer. That way the truck and trailer stop in unison

 

Thanks for the help. I had one of those hydraulic type of controllers years ago, it was probably the best controller I've ever had. I've always wanted to develop a hydro-electric brake system. It would use an inertia based electric controller which would operate an electric servo to push in on a master cylinder mounted on the trailer chassis. Think of it as a combo of a surge brake w/an electric controller.

 

The electric over hydraulic brake system you describe already exists in some high end fifth wheels and yes, 3 volts is the normal maximum you will see using the brake pedal at rest in a brake controller with an accelerometer as found in all moderately priced to high end controllers.

You can buy a controller model that reads brake pedal pressure in your truck and operates the trailer's electric brakes, if you like MaxBrake™ - Hydraulic over Electric Variable Brake Controller

The best high-end electronic controllers do an amazing job of matching trailer brake output to the rate at which your truck is stopping and with their built-in diagnostics make troubleshooting a breeze.

My two cents,

Steve

 

I put a Maxxbrake in my pickup, It was by far and away the best $250 I spent on the truck

 

[QUOTE=Diesel_Brad;12002166]I put a Maxxbrake in my pickup, It was by far and away the best $250 I spent on the truck[/QUOTE

Have never owned one, but owner reports seem consistently good.

Steve

 

Thanks for the reply! I don't know what type of controller I have, it came out of a parts truck from last summer, I'm sure it's not a high end unit but it will work for now. I will definitely look into the hydro over electric controller.
At least it seems that my hybrid brake system was a decent idea!

 

Your hybrid system is interesting. What lots of folks who RV and have them don't know is the industry did not design them to improve braking ability, which they think electric brakes by themselves can easily handle.

The hybrid idea came about as they were searching for a way to improve reliability due to folks not maintaining their electric systems. From their perspective, the hybrid systems used disc brakes in RVs actually react more slowly than the all electric system as the hybrid has to operate a pump to activate the brakes. Not really a great difference, but I thought it was an interesting bit of trivia.

Steve

 

I ran into an interesting glitch today. I accidently turned on the hazard lights and I noticed that the red LED on the brake controller was blinking in unison with the dash board indicators. It doesn't do it w/ the turn signals, just the hazards.

I'm gonna go out on a limb and assume that it isn't supposed to do this? I tapped into the 'cold' wire on the brake light switch for the brake signal for the controller so I'm at a loss as to what the issue might be.

 

I think you need a "pulse preventer." You can probably find one at most places that carry electric brake controllers.

 

Yup, you need a pulse preventer. The hazards are backfeeding the brake light circuit, and the controller thinks you're pushing the brake pedal...