Blower only runs on high

WHAT MATTERS IS NOW ,NOT THEN.
2nd speed blower is dead.
so is , not the blower, if high works
it is
1: bad resistor block
2: bad control
3: bad wired from there to there. 1,2.
it's not a fuse
the car CAM NEW WITH 2 OPTIONS, AUTO OR MANUAL HVAC.
THE CONTROLS ARE NOT THE SAME.
AUTO HAS NO RESISTOR BLOCK AT ALL , IT USES TRANSISTOR MODULATION. IN THE CONTROL HEAD.
SO YOURS IS MANUAL
AND CAUSE IS ABOVE, 1,2,3
LEARN TO USE A VOLTMETER.
THE BLOWER DC MOTOR IS GROUNDED, AT TERN :"A"
THis pin X
must be 12vdc, speed 2 selected.
if is 12vdc the resistor block is bad (or its wires)


manual.controls. as you can see the resistor is tricky series type
so of 2nd Resistor burns open speed 2 and 3 fail but never 4.
if 3r RES burns open speed 3 lost but not 2 and not 4.
and not 1.
speed 4 is relay controlled, and pin C lower. right.

use a voltmeter and win the prize, SOLVED

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.

Could be a number of thing's ! Testing the electrical circuit is the way to find out what's wrong . Using a wiring diagram and a DVOM - digital volt ohm meter . Videos on youtube showing how to test it ! Without testing i would only be guessing . Does it work in high speed ? In high speed it by-passes the resistor . If it doesn't work in any speed more then likely the blower motor is the problem !
Air Speed
The HVAC control assembly applies ground to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:
• Low speed--3 resistors
• Medium 1 speed--2 resistors
• Medium 2 speed--1 resistor
When the operator requests High speed, the HVAC control assembly applies ground directly to the blower motor through the high blower motor control circuit. The resistor card has a fusible link which, if blown, will require that the card be replaced.

Blower Motor and Resistor Diagnostics by Wells

in review
the fan speed resistor is new
you bench tested the blower motor
12 volts test ..only runs it at full speed
if cabin filer want changed the blower motor would run hotter

could be the motor brushes or bush/motor bearing when slowed
you might want to inspect the brushes and clean the dust out of the motor
if no better
does that have climate control ?
might be the fan switch itself or the earth isnt so good

Its faulty blower motor resistor. The low and medium speed on blower motor is controlled by resistor and its actual speed is high. So because resistor is not working, blower motors actual speed which is high is working.

It can be faulty blower motor or faulty blower motor resistor. Get the blower motor inspected. If it's faulty it has to be replaced.

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For blower motor testing and replacing, check the link below: ----

Blower motor Testing/replacing for all vehicles?

http://repairhelpcenter.blogspot.in/2012/02/blower-motor-replacing-for-all-vehicles.html

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These will help.

Thanks.

check for bad connection on wiring, turn blower on high and wiggle wiring under dash around blower motor and resistor area

May be but next to the blower motor is the blower control module this has a series of resistors in it to change the current flow to the blower motor ,.When you call for high speed on the fan it bypasse's the resistor module, on all other speeds it runs through the resistor. so check for power going into the blower module from the control panel on some speed other than high if power is at the module control panel is ok. if not blower module is bad

Does it still sound like its on high? If so you could have your vents blocked/restricted or your blower is not blowing on high speed. Usually a blower resistor if not blowing at max or not blowing at all speeds

The high speed setting on any blower bypasses the dropping resistor completely so I suspect you have a failing switch contact. If you can access it, some 'contact cleaner' from an electronic supply outlet may help to restore its operation but generally, once a switch develops problems, it will fail again.