Blower motor does not work on high

94 CHEVY Silverado ????,heat/ac fan not blowing. K1500?????? Hear clicking when selecting l'm, SET high but not blowing! WITH AIR OR NO A/C? FIRST IS FUSES, MAKE SURE THE BLOWER FUSE IS NOT BLOWN.
EASY NO? CHECK ALL FUSES FIRST. ON ALL ELECTRICS FAILING OF ANY KIND.
BAD FUSE, BAD WIRINIG , BAD CONNECTIONS. OR EVEN BAD RELAYS TO THE BLOWER OR BAD SWITCH BLOW.
THE OLD CARS , HAD A SPEED BLOW , RESISTOR BLOCK
THAT FAILS ON ALL SPEEDS BUT HIGH, SO ITS NOT THAT.
OWN A VOLT METER????
HERE IT IS, ANY OF THIS CAN FAIL THIS OLD
WE USES A VOLTMETER TO FIND THE POINT OF FAILURE.
A SHORTED BLOWER MOTOR CAN BLOW LEFT SIDE TOP
FUSABLE LINK.RIGHT FUSE BLOWN MAKES THE CONTROLLER DEAD.

The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.

HVAC Blower Controls Circuit Description
The blower motor is a variable speed motor. The motor operates at a higher rate when voltage is increased to the maximum level.
The blower motor resistors reduce the voltage supplied from the A/C FAN fuse (LH IP Accessory Wiring Junction Block) when the blower control is set at low and medium speeds (speeds 1-4). The blower motor relay is energized when the Blower Motor Control is set to the High position. This removes the blower motor resistors from the circuit and battery voltage is then applied directly from the HVAC BLO fuse (RH IP Accessory Wiring Junction Block) to the blower motor though the relay switch contacts. The blower motor then runs at high speed.

That is the blower motor relay, probably . You have all speeds but high ? High speed has a direct path to the blower motor through a high blow relay . All other speeds go through the blower motor resistor assembly . This relay is part of the blower motor resistor assembly > That is if you have manual HVAC system .
Blower Motor Resistor Assembly (CJ3)
Under the right side of the I/P mounted to the HVAC box next to the blower motor.

Switch or Motor may be bad .

burnt connector means high draw from motor . pull the blower motor and check if it turns easy.

Three possibilities. AND all you can do yourself!
1. Hi/Low Blower Relay. However these usually fail on low and works on High.
2. Blower Control Switch.
3. Blower Motor Resistor.
If you do not have one: buy a Voltmeter, available for $6 at Walmart.
If you do not have one: buy a Haynes or Chilton Manual at most auto parts stores for $20-$25 dollars. I say this because you are obviously going to keep this vehicle. It will have most of the information with pictures to assist you.
Quickest way to determine which one?
Finding the Resistor....Go on line to autozone.com or advanceauto.com. Answer the questions on year, make, model and engine and go to "look up parts" or click on "Replacement Parts".
Pull up the Hi/Low Blower Relay.
Know you know what you are looking for.
This Relay is located near the Blower Motor.
The System goes: Switches, Relay and/or Resistor, Motor.
Unplug the electrical connection from the Switches going to the Relay.
Turn the engine on. Turn the Selector to Low and using a voltmeter, check for voltage coming from the Switch. Turn to High and rechaeck for voltage coming fom the Switch. No voltage on High? The Switch is bad.
Do the same with the Relay to Resistor connection and or Relay/Resistor to Motor connection. Check the Low and the High voltages.
Let me know if this helped or if you have additional information or questions. Feel free to contact me at FixYa.com!

If the blower is coming on when you put it on #4 then it is definitely a switch issue. Try replacing the switch.

as you said relay is good,try to check 4 connection of relay,pullout relay,check if there a 12 volts supply,, a 12 volt control by ignition sw.,connection to blower motor, the last connection is to the switch mostly connected to ground.

Remove the hush panel under the dash and unplug your blower motor turn the knob and see if its getting power. If it is replace the blower motor. If your heater seems to work on high but not the other 4 settings. replace the blower motor resistor and pigtail (same general location as blower motor)

this is not a problem with thw switch or motor. There is a resistor that is mounted inside the dash on the pasenger side that controls the speed of the blwer..these have a tendency to burn up after 10 years or so... replace the resistor, and you will be fine!  http://cgi.ebay.com/ebaymotors/Toyota-Truck-A-C-Heater-Fan-Resistor_W0QQcmdZViewItemQQcategoryZ33548QQihZ016QQitemZ260344846266QQrdZ1QQsspagenameZWDVW#ht_500wt_1230