1976 C30 Trailer Brake Controller

[ProRedneck]

I would like to add a trailer brake controller and 7-pin connector to my '76 C30 Silverado. Any suggestions on the best way to go about that? Thanks in advance.

 

[MarineOne]

Pretty easy instal I have linked the products I would use. They just tap into factory tail lights

https://www.etrailer.com/Accessories-and-Parts/etrailer/ETBC7.html

https://www.etrailer.com/Brake-Controller/Chevrolet/C%2FK+Series+Pickup/1976/90885.html?vehicleid=1976202925

 

[75gmck25]

I’ve considered this upgrade to my K25, and it seems that one of the marine-grade fuse/relay boxes might be a good choice to hold everything. They are mostly waterproof, so I could locate it a variety of places. Something like this seems like it would work. https://www.amazon.com/dp/B08KHVHLL5/

Most of the installation is easy, but you will need to add a constant 12 volt fused power circuit and a trailer brakes circuit to have a fully functioning 7 pin controller.

7 pin plug upgrades
- constant 12 volt circuit, often with a 30 amp fuse and relays. Provides constant power to the trailer to charge battery, run aux lights, power a camper, etc.
Trailers set up for electric braking will usually have a small battery to power the brakes. If the trailer detaches and pulls the emergency pin it will activate the trailer brakes even if it’s no longer connected to the truck.
- trailer brake activation circuit, often 30 amp. Connect from plug to controller using a relay and use it to actuate the electric trailer brakes
- ground wire (upsize it from what is used on the small 4 pin connector)
- backup lights (these are not part of a standard 4 pin plug)

These wires are in a standard 4 pin plug, and can be directly connected to the truck, or you can use relays. I recommend using relays.
- left turn/brake
- right turn/brake
- running/tail lights
- 4 pin plug will have a ground wire also, but it’s probably undersized for trailer brakes

 

[Buck69]

I remember having aftermarket brake controllers in older squares that tapped into the brake line and worked proportionally directly with the brake line pressure. Is that not a thing anymore? It is still built into newer vehicles that way.
I ask, because it is something I would like to add for a 7,000 lb trailer with an EH brake system. It appears the ones available nowadays only use an adjustable (calculated) delay and max gain triggered off of a on/off switch? I could see them being a problem in an emergency situation when immediate and hard braking is required on poor road conditions.

 

[HotWheelsBurban]

I’ve considered this upgrade to my K25, and it seems that one of the marine-grade fuse/relay boxes might be a good choice to hold everything. They are mostly waterproof, so I could locate it a variety of places. Something like this seems like it would work. https://www.amazon.com/dp/B08KHVHLL5/

Most of the installation is easy, but you will need to add a constant 12 volt fused power circuit and a trailer brakes circuit to have a fully functioning 7 pin controller.

7 pin plug upgrades
- constant 12 volt circuit, often with a 30 amp fuse and relays. Provides constant power to the trailer to charge battery, run aux lights, power a camper, etc.
- trailer brake power circuit, often 30 amp. Connect from plug to controller using a relay and use it to actuate the electric trailer brakes
- ground wire (upsize it from what is used on the small 4 pin connector)
- backup lights (these are not part of a standard 4 pin plug)

These wires are in a standard 4 pin plug, and can be directly connected to the truck, or you can use relays. I recommend using relays.
- left turn
- right turn
- brake lights
- 4 pin plug will have a ground wire also, but it’s probably undersized for trailer brakes

4 pin also has a running/parking lights circuit.

 

[75gmck25]

My error. You are correct, the fourth wire is running lights, not a separate brake wire. I also clarified that the turn signal/brake bulbs are a dual duty circuit.

I think they stopped connecting into the truck’s hydraulic vehicle brakes to measure braking a long time ago because it was considered a safety hazard to modify the OEM vehicle braking system. Some of the new trucks with built in controllers might work that way, but it was designed into the truck.

The newer electric controllers are usually one of two types:
- all electric, with an internal algorithm to control brake activation (time the pedal is pressed, rising voltage, etc.) . They can be user-adjusted for sensitivity.
- mechanical activation switch inside the electric controller. The one I have is a simple pendulum mechanism inside that swings forward and activates the trailer brakes when you stop the truck. It has a slider control in the front panel to set sensitivity. I’ve used on my Ford Expedition, but never on my K25.

 

[SirRobyn0]

I remember having aftermarket brake controllers in older squares that tapped into the brake line and worked proportionally directly with the brake line pressure. Is that not a thing anymore? It is still built into newer vehicles that way.
I ask, because it is something I would like to add for a 7,000 lb trailer with an EH brake system. It appears the ones available nowadays only use an adjustable (calculated) delay and max gain triggered off of a on/off switch? I could see them being a problem in an emergency situation when immediate and hard braking is required on poor road conditions.

No that is not a thing anymore.

Right so the modern ones use delay and gain, but the better ones have an accelerometer built into them so when you stab the brakes in the truck the trailer brakes apply just as hard. They work every bit as well as the old ones tied into the line, without the risk of fluid leakage. I have a prodigy trailer brake controller in my truck and regularly tow two axle flatbed. That controller is so much better than the ones without the accelerometer I used to have. I'll never go back.

 

[Buck69]

No that is not a thing anymore.

Right so the modern ones use delay and gain, but the better ones have an accelerometer built into them so when you stab the brakes in the truck the trailer brakes apply just as hard. They work every bit as well as the old ones tied into the line, without the risk of fluid leakage. I have a prodigy trailer brake controller in my truck and regularly tow two axle flatbed. That controller is so much better than the ones without the accelerometer I used to have. I'll never go back.

Does your trailer have EH brakes? Another concern I have with the current ones during normal operation, is what happens with the trailer (with EH) brakes while stopped at a traffic light? Does the controllers let the trailer brakes let off or do they sit at full pressure even though the tow vehicle has let off?
With my '08 2500's integral system, while stopped at a light, you can hear the pump on the trailer load/unload proportionately to what my foot is doing on the pedal.
Sorry, if my '86 can handle pulling my ocean boat, going to be dumping the '08.

 

[Turbo4whl]

I remember having aftermarket brake controllers in older squares that tapped into the brake line and worked proportionally directly with the brake line pressure. Is that not a thing anymore? It is still built into newer vehicles that way.
I ask, because it is something I would like to add for a 7,000 lb trailer with an EH brake system. It appears the ones available nowadays only use an adjustable (calculated) delay and max gain triggered off of a on/off switch? I could see them being a problem in an emergency situation when immediate and hard braking is required on poor road conditions.

As stated not a current item any more, but you can still get one. I towed a lot with my Kelsey-Hayes controller. Hard part about adding a new one now, no adapter fittings for the master cylinder.

You could cut the rear brake tube near the master cylinder, flare both ends and add the inverted seat tee fitting. Was easy back in the day, buy the controller, look on the chart and buy the correct adapter fitting for your master cylinder application.

This seller has new old stock for $50


https://www.ebay.com/itm/185610604344

You must be registered for see images attach

 

[SirRobyn0]

Does your trailer have EH brakes? Another concern I have with the current ones during normal operation, is what happens with the trailer (with EH) brakes while stopped at a traffic light? Does the controllers let the trailer brakes let off or do they sit at full pressure even though the tow vehicle has let off?
With my '08 2500's integral system, while stopped at a light, you can hear the pump on the trailer load/unload proportionately to what my foot is doing on the pedal.
Sorry, if my '86 can handle pulling my ocean boat, going to be dumping the '08.

If by EH you mean electrohydraulic no, if you mean electromagnetic then yes, as in they are fully electric no hydraulics involved in the trailer brake. I honestly have no idea what the trailer brakes are doing while stopped at a light, other than they are applied, but to what degree IDK. Given that the controller can tell if your facing up hill, down hill, flat, stopping or accelerating, I'd feel comfortable to say that they'd be applied as much as needed.

FYI my trailer and tractor combined are somewhere around 6,000LBS. Maybe, my trailer is an open trailer that the PO added 2 foot tall steel sides on to. I'm sure there is a couple hundred lbs of metal in the sides, so it's likely a bit more than 6K. Regardless my trailer is going to come in a touch lighter than yours. I have never, not even one time have I had an issue with the trailer brakes not doing what they are suppose to, unless it was my fault, for example unloading the tractor and forgetting to switch modes on the controller, resulting in the brakes locking up, but that's my fault not the controllers. You could look up the prodigy controller manual online or call the company to find out what it is doing at a stop light.

 

[Buck69]

If by EH you mean electrohydraulic no, if you mean electromagnetic then yes, as in they are fully electric no hydraulics involved in the trailer brake. I honestly have no idea what the trailer brakes are doing while stopped at a light, other than they are applied, but to what degree IDK. Given that the controller can tell if your facing up hill, down hill, flat, stopping or accelerating, I'd feel comfortable to say that they'd be applied as much as needed.

FYI my trailer and tractor combined are somewhere around 6,000LBS. Maybe, my trailer is an open trailer that the PO added 2 foot tall steel sides on to. I'm sure there is a couple hundred lbs of metal in the sides, so it's likely a bit more than 6K. Regardless my trailer is going to come in a touch lighter than yours. I have never, not even one time have I had an issue with the trailer brakes not doing what they are suppose to, unless it was my fault, for example unloading the tractor and forgetting to switch modes on the controller, resulting in the brakes locking up, but that's my fault not the controllers. You could look up the prodigy controller manual online or call the company to find out what it is doing at a stop light.

The trailer is electric over hydraulic with 2 5k disc torsion axels. If fully loaded with fuel, water and gear it is likely closer to 8 on the scales. The truck has 4.56 gears so hopefully no pulling issue.
I did read up on the (P3) prodigy controller last night before calling it a day. Looks like it has solid reviews with EH mode for systems like mine.
Thanks!

 

[SirRobyn0]

The trailer is electric over hydraulic with 2 5k disc torsion axels. If fully loaded with fuel, water and gear it is likely closer to 8 on the scales. The truck has 4.56 gears so hopefully no pulling issue.
I did read up on the (P3) prodigy controller last night before calling it a day. Looks like it has solid reviews with EH mode for systems like mine.
Thanks!

Glad I was of some assistance. 4.56's will move it fine. I've got the 305 and 3.41 gears and manage a 6K trailer ok. I would like to go to 4.10's, but haven't got round-tuit lol