artjohn

Purchased my HHR to tow behind my motorhome. I am installing a brake system on the HHR so its brakes will be applied when I apply the motorhome brakes. The brake system has a small transmitter that signals my control box in the motorhome that the brakes on the HHR are applied. This transmitter is activated with 12v from the tow car brake switch. The HHR brake switch has 3 wires, none of which has 12v. I measure about 5v on one of the wires. Can anyone enlighten me as to how the HHR brake switch works? 3 wires, why? Where can I get the 12v I need to activate my brake transmitter?
I've installed this system on other autos, but I always had 12v at the tow car brake switch to connect to, and there were only two wires on the brake switch. The HHR has 3 wires and none of them have 12v.

charlie pachanga

You need 12volt to power the electric actuator and to aply brakes if your break away safety becomes disconected? Just hook it up to the Cig lighter. If it has a higher amperage draw than 20 amps then go straight to the battery.

artjohn

I guess I wasn't completely clear with my need. I only want the 12v when the brake pedal is depressed (in the HHR). That is why I wanted to hook up to the brake switch.

shawnvw

The problem with the new vehicles' brake switch, is that it is no longer a switch. It is a pedal position sensor. Like you already know, it works on a 5v system. When the brakes are applied, it sends 5V+ through a variable resistor, that is the brake switch, to the BCM.
The unfortunate part of all this, is that all 3 brake lights on the vehicle, are on 3 separate circuits. I'm not 100% sure of what you are trying to do, but I think you want the brake lights of the HHR to light when you hit the brakes on your motorhome? If so, you will have to tap into all 3 brake circuits, MAKING SURE YOU DIODE ISOLATE each circuit. If you only want a signal from the HHR to the motor home, you can use the signal from the Center High Mount Stop Lamp(CHMSL), wire locations and colors below...


LS Brake light\turn signal - BCM Connector 3 Pin A9, yellow wire
RS Brake light\turn signal - BCM Connector 3 Pin A12 Dk Green Wire
CHMSL - BCM Connector 1 Pin 31 White Wire

artjohn

I understand what you are saying about the 5v system and better understand what I am faced with. If you can help me some more, I would appreciate it. My problem is not getting the brake lights on the HHR to work when I apply the brakes in my motorhome. That has been wired and the diodes have been used. That all works. I have a small box on the dash of my motorhome that informs me (with a red light) that the brakes on my tow car have been applied (keeps me from driving down the road should the tow car brakes come on when I don't want them to). This box receives a signal from a small transmitter in the tow car. The transmitter receives its signal to transmit from the 12v received from the brake switch. My problem is where do I get the 12v to activate the transmitter if I can't get it from the brake switch?

charlie pachanga

Get it from the Center high mount stop light (CHMSL) out of the BCM. Connector 1 pin 31 as ShawnVW has stated.

artjohn

Thanks for the input. I will hook it up as directed. Sounds like it will do what need to be done for me.
To me, this is just another example of what the auto mfrs are doing to eliminate the "do it yourselfer".

mikeross

I have done this one. But the brake away safety becomes disconnected over and over again. Do I have to change my brakes?

Kathy Martin

We are removing a tow braking system. I have no wires coming from the brake pedal resistor and need to know where they go. Do you have a brake light diagram?