I posted some youtube videos on how to upgrade an alternator and how to repair some of the problems that come up. Here is the llnk

https://www.youtube.com/watch?v=aof_kAFDYw4&feature=youtube_gdata_player

 

I saw both videos and noticed your RABS proportioning valve has a black connector between the two top brake lines. My '97 does not have that connector, only a 3/4" bolt screwed into the center hole where the connector would connect to a sensor. And yes my RABS light is ON all the time. I've followed all the troubleshooting Service Manual steps including the Code from the diagnostic wire/flashing light. Got a code 12, "low brake fluid level" which is not.

 

Check your master cylinder inside. See if the float is sticking or stuck down. It can also be bad float sensor or the wiring that comes out has a short or bad ground back to the Ab s monitor under the ash tray.

I might add your just need the upper plastic part with the sensor in it. cheap part from yard and was used in many new trucks still. Might get one and see if goes away.
Do you have the factory service wiring manual? If not I'll see if I can post it, some others can dl it.

 

yes, I have the Ford Service Manual for the 1997 Aerostar but no illustration of the fluid level sensor at the Master Cylinder or instructions to replace it, I thought you have to replace the entire MC.

 

Your not going to, the sensor is part of brakes resevior when you buy it. all you can check is the pins on both ends and make they are straight and make good contact. You can check them with an ohm meter. check each one in pairs 1 2, 2 3 and 1 3, see what it is when the float is up then down. I bet the float is bad in the resevior on top of the master cylinder.

 

ok thank you, I already tried checking the float but it "appears" it might be stuck at the bottom of the reservoir, (doesn't move up or down), otherwise I have no clue what I'm looking for. Is the float located in the front or the rear of the two inner compartments of the MC ?

geez, something so simple and I can't figure it. Sorry but I've never messed with this RABS business before or even an Aerostar MC, my 1992 Aerostar had RABS and it never gave me any issues.

 

The float is right below the fill cap. Its round and has a post in the center of it. you should be able to push it down with your finger and it should float right back up without any help. When you take the cap off its right there where you can see it. if its stuck down tap it with your finger. you have to drive it some before the light goes out.

 

ok, that tells me it's stuck down, there is absolutely no round float to be seen when I remove the cap on the reservoir, nothing I can push down and returns up. Going to check again in the morning. Many thanks.

BTW: I had already checked the wiring at the connector per the service manual troubleshooting steps, and it came out ok, also cleaned the contacts at both male and female connectors, but the light stayed on. It must be the float.

 

I have no float, zero, nada, no post either, I stuck my finger in there, I tried a pick tool, nada. nothing, I can feel a rounded "base" at the bottom, in other words, a concave base as if the ball would "sit" on it, otherwise no ball anywhere.

is the plastic reservoir available by itself with the float? or do I have to replace the entire master cylinder?

 

Just the resevior not the master cylinder. The sensor is in it. if you get a used one check the wiring connection pins make sure none are bent or dirty and used dielectric grease. I might post a video on that as well. It rained here so I have not done the new alternator rebuild. I want to paint it with rm paint and clear coat it. still waiting for them mix it for me. They put it in pressure can so I dont need a paint gun, pretty neet with factory matched paint in it.

 

I found that clearcoat from cans don't last very long. After just a few months of the sun beating down on it, it starts to haze up, and a few more months, it starts to flake off. Then you have to scrape it all off and repaint. You may not have this problem with an alternator that seldom sees the sun, but engine heat may cook off the clearcoat as well. Maybe CC rated for engines will last longer.

 

I found a new reservoir with float and switch using the parts locator thru my Ford dealer, and went ahead and ordered it. Many thanks for the help and I look forward to the video.

 

This is factory rm paint out of the quart can. They color match it then put it in a pressured can with a specific spray nozzle. comes out like a custom spray gun. this is not over counter auto store stuff you buy. It works great when used on properly prep surface. It will go on the alternator and mounting bracket.

 

While the 1997 Aero service manual shows this type of master cylinder, with the float directly under the cap . . .

(click on images for larger)




. . . our later Aeros don't have the cap over the float:




I'm guessing that Ford is showing a Ranger master cylinder in that pic. It does go on to say:[later]

This is an odd system. Hmmm. Note this warning in the FSM:IOW, you could have a failed diode causing your spurious Code 12. It says, "Diode/resistor element located three inches left of the cluster connector takeouts in the instrument panel wiring harness." Not fun. Every time I have to pull my cluster, I pine for my old '89 Aero, where something like six screws retained the dash panel over the top of the cluster, making changing bulbs or whatnot a ten-minute operation, with no danger of breaking plastic/steel retaining clips!

Electrically:


Incidentally, I don't find the Pressure Differential Warning Switch to which that diagram refers (connector C164). The connector reference says it's under the master cylinder, but I just braved the 26° cold with a flashlight, and I sure don't see either that connector or any switch on the Combination Valve under the master cylinder.

 

Looks like there's a variety of things that can cause a RABS code 12.