OK guys, panic time for me! My '95 E-4WD Aerostar has flashed code 3 on and off for a while. Now the code is permanent. I checked and it has to do with discontinuity in the front output shaft speed sensor. Cleaned all contacts and wiring harness really well. Didn't do it. Out of curiosity, I pulled both sensors and probed the resistances between pins. Sure enough, the front sensor is dead as a door nail. Now I need a sensor. The problem is I couldn't find a source online, and the local dealer really wants an arm and a leg for these things. Does anyone have any idea? Perhaps one of you works for Ford and can buy it cheap for me I tried the local junkyards and was told this is Southern California where people a) don't drive Fords and b) even if they do, they don't drive 4-WD and c) if they drive 4WD they don't junk them

 

Copper,

I've got an old one that I'm not sure if it is good or not. (I replaced it with no change to my problem) Please let me know what resistance I should see between the pins, and I'll check mine. If it's good, I'd be glad to put in your hands.

 

Hi B2trausch:

If you measure the resistance between the two outermost pins, I think that should read about 1000 ohms. Between the center pin and one of the outer pins (not sure which one) it should read about 2200 ohms. Between the center pin and the other outer pin it should be about 3200 ohms. Please let me know what your readings are.

Thanks

 

I'll be heading to a junkyard today to see if I can spot some center captians chairs. I'll see if I can grab one.

 

Hi Muffinman:

Thank you very much. I know I can count on a fellow Texan Used to live in Houston until the harsh summer drove me out

 

Well I went and every AWD had them cut out "Not that many to start with". Not all the yards were open today, So I'll hit them Monday on the way home from work.

 

Thank you for trying. I visited some of the local junkyards here, but they have absolutely no AWD Aerostars.

 

Copper,
I checked the sensor with a very old analog meter. My digital meter is at work, and I'll check them again with that today, but here is what I have so far. Holding the sensor at the 6 o'clock position, looking at the connector, the far left pin I'll call #1 center #2 and right #3. Pins 1 to 2=2800 ohms 1 to 3=1500 2 to 3 = 4700.

When I get home tonight, I'll give you more accurate results, but I think the sensor may be good. My E-mail is b2trausch@hotmail.com.

 

This probably sounds silly, but having that sensor de-gauzzed at a TV repair shop may make it work again.

 

No! Do not de-gauss the sensor! A lot of those magnetic sensors have a permanent magent in them to make them function. Even if they don't, a strong magnetic field applied to them can burn out the coil of wire inside.

The best test is still the resistance test.

 

Some of them have a piece of iron in them, which gets magnetic and stops the thing working. I guess the things to find out what it is. Perm magets do not live long in that environment anyway.

 

BarryFS,

I think all those magnetic sensors have to have a magnet in them, unless the device they're trying to sense motion from has some kind of magnetic trigger on it. Then the sensor only needs to have an iron core surrounded by a coil of wire to pick up the change in magnetic field.

So magneto ignition systems have a rotor with some parts of it magnetized that fly by a coil of wire around an iron core. Or in a tape player, the magnetic tape runs by a head and the variations of the magnetic field on the core is picked up by the wire coil around the core. Such a head does not have a magnet in it for obvious reasons.

But the magnetic sensors that we're talking about are usually placed near some iron part with teeth, such as a cog. When the teeth move by the magnet, they disturb its field, and this change is picked up by the coil. In the last two cases, it would be a really bad idea to try to degauss them with a large electromagnet, since the wires in the coil are very delicate, and a strong magnetic field will burn them out. (There are special degaussers for tape heads, but they're almost never used anymore because new head meterials do not get magnetized.) With the magnetic sensor, you definitely do not want to degauss the magnet; even if you manage to do so without burning out the coil, the sensor will be useless.

 

The mag pick-ups I use on diesel engine flywheels are literaly a piece of Swedish soft iron, with about 20 turns of wire. These get magnetic over time, and quit (slowly).