Brake warning light, Amp light

CheeseSnake · #1 (**permalink**) 02-22-2006, 06:35 AM

I bought my car already built in 1998, and I'm going through it now that I have time to do a lot of upgrades. Anyway, the guy I bought it from had overheated the brake fluid due to the proximity of the proportioning valve to the headers (that was his story) - there is about 2" of clearance between the prop valve and the headers at the front of the drivers footwell. Since I bought it, the red brake warning light has been on whenever the car is running. There is a small red switch screwed into the prop valve with a plunger on the prop valve side and two pins on the other side with wire #156-blue going to one of the pins. There is no ground directly to the prop valve. Where can I get a new switch, and how should I test it? I assume it is meant to signal loss of brake pressure.

Also, the amber amp light. Is this light supposed to be on all the time with the car running? I don't remember it being on but I cant start the car right now ( carb and a lot of other stuff is off the car at the moment) and the light is on when I turn the key to "run". Is this normal, and if so, where does the light get it's signal from?

dscott · #2 (**permalink**) 02-23-2006, 08:21 AM

The amber light stays on until the engine is running. The voltage from the regulator is where the signal comes from. Once the proper voltage is reached the light goes out. The brake warning light signal does come from the prop valve and is for low pressure. You can take the prop valve off and reset the plunger, you will need to take the prop apart to do this, or get a used one at a salvage yard. It's from a 1974 to 1978 Mustang II. We don't use them anymore. We have an adjustable valve that goes in the rear brake line only. The front is now a direct hookup. We no longer use the red light since there is no hookup for a light on the adjustable prop.
Don

CheeseSnake · #3 (**permalink**) 02-23-2006, 09:27 AM

Thanks Don.

So the amber light is for voltage, fed from the voltage regulator. Is it a direct feed from the regulator to the light, or is there some other device in the circuit that determines that proper voltage has been reached, and then signals the light to go off?

The red brake warning light. You mention "resetting" the prop valve. If the prop valve is in a normal condition, is the plunger on the red switch/connector depressed or extended? In other words does the switch activate the light when the switch plunger is depressed or extended? Would you recommend just changing to the direct hard lines for the fronts and an adjustable prop valve for the rears or just fixing what I have? The current prop valve on there is not adjustable so I am leaning toward refitting with the new setup.

Thanks again,

Jim

dscott · #4 (**permalink**) 02-23-2006, 09:00 PM

There is no other device in the circuit. The regulator is the only source for the voltage.

I would change the prop to the adjustable type. I don't remember which way the plunger goes in the stock valve but when you take it apart just reverse the way it is. It will be a little more difficult to change over but I think the effort is worth it. There is no provision for a light on the new prop valve.
Don

jwinkler · #5 (**permalink**) 04-10-2006, 11:16 PM

My red light came on a few weeks ago, and I discovered I had no fluid in the rear brake reservoir (turn-key build, so I'm guessing it uses the MII prop valve).

I've added fluid and bled the rear system, bled the right front, and pumped the brakes, but still can't get the light to go off.

I took a test drive around the neighborhood, and the car stops just like it did (when the rear system was dry, the pedal had a little extra travel).

Does the adjustable valve work with the "stock" reservoir? Any way to reset the prop valve without taking it apart?

Thanks,

JLW

PS - I've also got an issue with hard stops. When I hit the brakes hard, the engine wants to die. Am I just emptying the rear float bowl, or might I have a vacuum issue?

dscott · #6 (**permalink**) 04-11-2006, 08:20 AM

I don't know of any way to reset the brake light other than take it apart. Maybe someone else knows how to do this. It would make sense that there's a way to do it. I don't think the problem with the engine would be vacumn. More likely the carb. The adjustable prop valve goes in the rear line only and will work with any master cylinder. You would need to run the front brakes direct to each caliper by running a line from the master to a "tee" and then a single line to each caliper.
Don