When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
There is a wire that is plugged into this valve. I cannot figure out what/where this wire is. Im putting the harnesses back on this build. Need help! Thanks Ken
There is a wire that is plugged into this valve. I cannot figure out what/where this wire is. Im putting the harnesses back on this build. Need help! Thanks Ken
Hi goldnut. Guessing you are referring to the brake proportioning valve. Not much experience with the 79 vette. I did however replace a brake proportioning valve recently on a 72 Malibu. The wire in this setup was connected to a warning light on the dash.
Everyone calls that a "proportioning valve", but that's not what it is. That is the brake system's 'distribution block'. Both front and rear system brake lines connect to either end of that block. Inside, there is a shuttle valve.
As long as there are no leaks in either system, that valve stays in its center position and both systems are active. If either front or rear develops a significant leak, the shuttle valve is thrown off-center so that the leaking part of the system is blocked off, thus stopping the leak...but that half of the system is no longer functional. So, the sensor in that block detects the shuttle valve being tripped, and sends a signal to that wire to turn on the BRAKE light in the dash. It's the same BRAKE indicator that lights when the emergency brake is actuated; basically, that warning light has two functions: e-brake is ON and/or the brake system has a big leak.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by 7T1vette
Everyone calls that a "proportioning valve", but that's not what it is. That is the brake system's 'distribution block'. Both front and rear system brake lines connect to either end of that block. Inside, there is a shuttle valve.
As long as there are no leaks in either system, that valve stays in its center position and both systems are active. If either front or rear develops a significant leak, the shuttle valve is thrown off-center so that the leaking part of the system is blocked off, thus stopping the leak...but that half of the system is no longer functional. So, the sensor in that block detects the shuttle valve being tripped, and sends a signal to that wire to turn on the BRAKE light in the dash. It's the same BRAKE indicator that lights when the emergency brake is actuated; basically, that warning light has two functions: e-brake is ON and/or the brake system has a big leak.
Correct me if I'm wrong, but the part that fits 78-82 models looks to have a non-adjustable proportioning valve piston in the rear of the block. Obviously, the switch piston is also in there at the center of the housing.
Look at the top, left of this picture. This is the forward lamp harness. The bulkhead connector is at the very top, left.
The wire for the proportioning valve is the very first one you see after the connector. It is tan and the one with the strange looking white plug. It branches out immediately after the bulkhead connector and never even makes it into the wire loom.
Thank you very much Mike. That is the info I was looking for. I did not put the forward harness on yet, so that explains why I could not find it. Appreciate your help. On to the next project. Rear window clips and trim!
