while last night it got stranger. I pushed the ebrake to the floor, the brake light got brighter and then the ABS light came on too. I pulled the ebrake release and the brake light went off, but the ABS light stayed on. So then is turned the truck off and restarted it and both lights went away. I went for a drive and within 2 miles the brake light was back on. So when i got home i did the same thing i did before except the brake light stayed on this time. Im really puzzled now.
It sure seems to me like an electrical problem. The intermittent nature of the problem leads me to say this. My caveat being, that I have not inspected the truck in person, so I cannot say definitively.
Do you have an ohm meter or a multimeter? It would help considerably in troubleshooting this problem. If not, I'd recommend getting one, when you have one it's amazing how many uses you find for them. And they are not that expensive.
The red brake warning light serves 3 funcitons.
1. The parking brake is on
2. The brake fluid is low
3. The brake hydraulic system has failed (on cars with a proportioning valve. On this model Ranger, it seems that when you run low on fluid is soon enough to tell you the brakes have a hydraulic failure)
There are 3 ways the red light turns on:
1. When you are starting the car, the brake comes on with the starter so you can verify the bulb is working. Check this, does the light come on when the key is in the start position?
2. When the parking brake is set.
3. When the fluid is low in the MC.
You checked the brake fluid level, so it's not 3.
You set the parking brake and the light got brighter. I think that's significant in that if there's a short somewhere, it might be a high resistance connection and be letting the light on, but when it has a good ground (parking brake set) more current can flow and the light comes fully on.
Let us know if you are seeing the brake light on when the key is in the start position.
If I was to take a shot in the dark, I'd say look at the bottom of the MC reservoir. There is a gray plastic plug on the passenger side with three wires going into it. Unfortunately, while Ford did a good job making most of the electrical connections under the hood weather resistant, they missed this one. (at least they did on my truck) There is a black wire (goes to ground) a dark green/yellow stripe wire (goes to the diode/resistor network for the brake warning light), and a Tan/light green wire (goes to the RABS control module and the ingnition switch). If either the dark green or the tan wires are shorted to ground it will light the brake warning light. Check these wires to see if one of them is loose or the connection is corroded and the wire has pulled out. If it has, the connecter can be dissassembled pretty easily. I'm going to be checking my Ford dealer tomorrow to see if the plug and pins are available. Will let you know what I find.
The service manual lists the following for a brake warning light on:
1. Brake fluid level low.
2. Wiring between Diode/Resistor network and module is shorted to ground.
3. Worn or damaged RABS II module.
4. Worn or damaged brake fluid level switch.
5. Loss of pressure in brake circuit (Aerostar only).
The last one is because the Aerostar actually does have the proportioning valve kimcrwbr1 mentioned, the Ranger does not. So by extension, if a Ranger looses pressure in a brake circuit, the brake warning light will not come on. Or if it does come on, it will be triggered by a different element.