93 wiper problems

My sons 93 LX wagon's windshield wipers only work in high and low speeds. The intemitten position is dead, and the park function does not work. The wipers just stop where ever they are when you move the lever to off. Can any one help?

I suspect it has to be the switch or the motor unit, but would like to figure out which before I just swap parts.

A voltmeter should tell you plenty. Measure the power at the motor with the switch in each position. If there is power there when on intermittent, then the motor isn't working right. If there is no power there, then it is the switch.

The wipers on these also have a "Black Box" under the dash that controls the intermitt wiper function. It has been years, but I have replaced a few. Can't remember what the actual name of the part is though.

Thanks for the replies. I finally got a day off and started checking the wiring.
I have volts to the motor when the switsc is in the low and high speed positions but not in the intermitten. I also have volts on the single blue wire tha a friend said is the park circuit. I have not been able to find a wiring diagram that covers these circuits. Does any one know which wire controls the intermitten and park circuit? Also, I will try to figure out the "black box" you mentioned. The wiring on my '93 is different from this '95. My post subject is wrong, the problem is on my 95, not the 93.

Does your intermittent setting have a single, fixed time interval between wipes, or can you vary the interval via a rheostat located somewhere on the steering column wiper switch? I have a diagram for the '95 Escorts but it only shows the latter arrangement.

If you have a single, non-variable interval then ignore this diagram as it will only mislead you but if it is indeed variable and if the interval control is integral to the wiper switch assembly then this diagram may be relevant.

http://img406.imageshack.us/img406/6418/wipers2ab0.png (http://img215.imageshack.us/img215/3302/wipersrl6.png)

Also, the switch-testing table which is referenced in that diagram:

http://img185.imageshack.us/img185/8391/wiperswitch2vq3.png (http://img406.imageshack.us/img406/7554/wiperswitchcq7.png)

Thanks Selectron, the diagram does fit our Escort. It appears the switch is bad. Hopefully I will get near a salvage yard this next month. The nearest is 90 miles south.