1991 1500 wiper motor w/delay. changed out the wiper motor assembly. I first tried to change out pulse board after it worked intermittently for a long time. it worked for a little bit while testing but started smoking. thinking maybe a bad rebuild I exchanged it again same problem. wondering if some one before me had this problem and messed with the plug wires? any thought on this?

You didn't take into account the wiper switch is a input to the BCM - body control module ,or do you know that ? The BCM controls wiper one an wiper two relay's to turn on the wipers .
Wondering if it is the PCB or perhaps a physical problem? Guessing never finds the problem . Reading how they work in factory service repair info should be the first step for someone that doesn't know .
Intermittent Operation
Windshield wiper DELAY operation is a low speed wiper motor function with a variable delay interval between the wiper motor cycles. The DELAY interval is determined by a series of 5 resistors within the wiper/washer switch. During DELAY wiper operation, the signal circuit voltage is further reduced through the DELAY resistors. The body control module (BCM) monitors the voltage on the signal circuit to determine the delay interval between the low speed wiper motor cycles.
If the wiper switch is moved from a longer delay interval to a shorter delay interval, the BCM will command an immediate wipe cycle and reset the delay timer to the shorter delay interval.
Additionally, intermittent wiper operation is vehicle speed sensitive. As vehicle speed is increased or decreased, the wiper interval will also increase or decrease.

Low Speed Operation
When the wiper switch is in the Low position, voltage is supplied through an internal resistor to the signal circuit. The body control module (BCM) monitors the windshield wiper switch signal 1 circuit and energizes the wiper 1 relay which will operate the windshield wiper motor. The wiper motor will operate at low speed, since the wiper 2 relay is de-energized. Low speed can also be commanded with a scan tool by commanding Wiper Relay Cmd. ON and OFF.
High Speed Operation
In the High position, the windshield wiper/washer switch supplies voltage to both the wiper 1 and wiper 2 relay coils. This energizes both relays and allows battery voltage from the wiper 1 relay switched output to the switched input of the wiper 2 relay through its contacts and out the switched output of the wiper 2 relay to the high speed circuit of the windshield wiper motor. The windshield wiper motor will operate at high speed. During HIGH speed wiper motor operation, the wiper switch signal circuit is at the LOW speed signal voltage, and the body control module (BCM) supplies redundant voltage to the wiper relay via the wiper diode.

Wiper/Washer System Components
The Wiper/Washer System consists of the following components:
• Windshield wiper/washer switch
• Body control module (BCM)
• Wiper 1 relay
• Wiper 2 relay
• Wiper diode
• Windshield wiper motor
• Windshield washer pump
• Windshield washer nozzles
• Windshield washer solvent container
• Windshield wiper arm and blade assemblies
• Windshield wiper transmission
• WIPER/SW 10A fuse
• WIPER 25A fuse
Refer to Master Electrical Component List.

DTC B3715 02: Front Wiper Relay Drive Circuit Short to Ground
DTC B3715 05: Front Wiper Relay Drive Circuit Short to Battery or Open

Your best bet , take it to a qualified repair shop.

You will need to diagnose this with a multi meter....on dark green terminal d at the wiper pulse board, with the wipers on any delay position, you should be reading .0005 Amps and 12 Volts and at the same time on the delay position one click below low(the fastest delay speed) you should be reading .0003Amps and 12V on terminal E gray wire, The purple wire (terminal C) should have 12V on high speed only. The yellow wire (terminal B) should have 12V when the key is on and the black wire (terminal A) should always be grounded....check all of that and we should be able to find your problem.
The Amperage should change on terminal E (the gray wire) with each position on the switch but the change will be very small. i.e. the first speed (longest delay) will read .000017 A, the second setting .00004 A and so on. Check that and let me know...(by the way, amps are checked in series with the connector so unplug it, place one probe in the connector and the other in the motor plug terminal. )

Change the wiper motor, and you replace the pulse board.. You can not buy the board separate from the motor.

Usually the park switch inside the wiper motor is the fault.

Just by your discription of the way it acted up i would think it's the pulse board . This pulse board screws on the wiper motor .

Go to Bing homepage

http://www.autopartswarehouse.com/shop_parts/wiper_pulse_module/cadillac.html

Replace the wiper module. Cardone at around $35-$50. This is the black cover under the hood, driver's side with 3 screws and about 4" x 4". Takes about 3 minutes to change.
A1 Cardone 81158PB Remanufactured Wiper Motor Pulse Board Module

maybe it's not problem with motor maybe is switch of wipers,or cabels that conect to wipers motor,or its fuse.

Hello, my name is Ben and I can help you with this problem. This is a very common problem with Chevy. You need what is known in most vehicles as a "pulse board". The pulse board is located inside the wiper motor control module. On many vehicles the pulse board is replaceable, unfortunately on your Silverado you must replace the entire Wiper Motor Control Module which is bolted onto the top of the wiper motor. To get to the wiper motor, first remove those little nut covers on the big end of the windshield wiper arms, if you slip a small screwdriver or your fingernail they just pop off. Now unbolt the windsheild wiper arms, before removing the wiper arms, mark their location on the windsheild with a grease pencil or magic marker. The arms are hard to remove, you need to kinda wiggle and pull at the same time, now that long plastic cowl needs to come off, those clips at the front edge just slide forward, then at each end lift up that rubber flap and remove those TORX screws. Remove the cowl and set it somewhere SAFE, it's easy to break. You will now see the control module mounted on the wiper motor, unplug the electrical connections and remove the TORX screws holding it to the motor. Assembly is the reverse of dis-assembly. If you have any trouble or questions, feel free to ask, Ben.

more than likely the pulse board loose at the wire connector. try wiggling the connector with wipers on (keeping hands away from wipers) then try tapping the motor with a small hammer.

try to any electricl loose contact electricl wiring circutry. tha may be.