Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
HiCustomer Thank you for asking your question on Just Answer.
Can you tell me if you have the Manual or Automatic system (automatic has a digital display that you would set the temperature on).
Also, can I assume you have AC too?
OK. Then you have two possibilities.
1 - The relay on the blower motor resistor pack has failed, and the resistor pack will have to be replaced.
2 - The fuse that supplies power to the blower motor when the switch is set to High is bad (in the upper-right of the schematic).
I would check that fuse first (in the engine wiring harness junction block) and make sure power is making it to and from that fuse.
Please let me know what you find or if you need further instructions.
Take Care, Greg A.
Here is a diagram of the Engine Wiring Junction Block.
I believe the fuse you will be looking for is # XXXXX (see table below).
Numbers shown are to reference position only - component not marked.
STUD 1 Fuse #1
Trailer Wiring / Automatic Level Control Compressor
ABS Fuse #2
Brake Pressure Modulator Valve (Pump)
IGN A Fuse #3
Starter Relay, Ignition Switch-IGN 1, TURN, SEO IGN Fuses
AIR Fuse #4
Secondary Air Injection Reaction Pump
RAP Fuse #5
Rap Relay, MIR/LOCK DR LOCK Fuses and SEATS Circuit Breaker
IGN B Fuse #6
Ignition Switch-Rap Relay, Wiper/Washer and SEO ACCY Fuses
RAP 2 Fuse #7
Power Window RF switch,Power Window RR Switch,Power Sunroof
STUD 2 Fuse #8
Body Wiring Provisions, Trailer Wiring
TRL R TRN 9
Trailer Turn and Stop
TRL L TRN Fuse #10
INJ B Fuse #11
Fuel Injectors 2, 4, 6, and 8, Ignition Coils, Engine Shutoff Solenoid and Sensor-Diesel
PARK LP Fuse #12
Park Lamp Relay, Headlamp and Panel Dimmer Switch-Park Lamps
FRT HVAC Fuse #13
Blower Motor (High Speed)
STOP LPS Fuse #14
VEH STOP and CHMSL Fuses, Trailer Wiring (LH, RH Turn and Stop Lamp)
ECM 1 Fuse #15
Vehicle Control Module (VCM)/Powertrain Control Module (PCM)-(from IGN 1 Relay)
CHMSL Fuse #16
Center High Mounted Stop Lamp
VEH STOP Fuse #17
Vehicle Stop Lamps
TRL B/U Fuse #19
Trailer Backup Lamps
INJA Fuse #20
Fuel Injectors 1, 3, 5, and 7, Ignition Coils, Glow Plug Module, Fuel Heat, Water in Fuel (WIF) Sensor, Wastegate Solenoid
RR HVAC Fuse #21
Rear Heater,Rear Blower Relays
VEH B/U Fuse #22
Vehicle Backup Lamps
ENG 1 Fuse #23
Mass Air Flow (MAF) Sensor, Camshaft Position (CMP) Sensor, Evaporator Emission (EVAP) Canister Vent Valve, Evaporative Emission (EVAP) C Purge Valve
ETC Fuse #24
Electronic Throttle Control (ETC)
IGN E Fuse #25
A/C Compressor Clutch Relay, DRL Relay, Rear Defog Relay, Secondary Injection Reaction Pump Relay
B/U LP Fuse #26
Backup Lamps, BTSI
ATC Fuse #27
Automatic Transfer Case (ATC) Control Module, Encoder Motor
RTD Fuse #28
Real Time Damping (RTD)
RR PRK Fuse #29
RR Park Lamps
ECM B Fuse #30
Fuel Pump Relay, Vehicle Control Module (VCM)/Powertrain Control Module (PCM)
O2 A Fuse #31
Heated Oxygen Sensors
O2 B Fuse #32
LR PRK Fuse #33
LR Park Lamps
RR DEFOG Fuse #34
Rear Window Defogger
TRL PRK Fuse #35
Fuel Pump Prime Port
RT HDLP Fuse #37
RH Headlamps (Hi and Low)
HTD MIR Fuse #38
Heated Outside Mirrors
LT HDLP Fuse #39
LH Headlamps (Hi and Low)
A/C Fuse #40
A/C Compressor Clutch
AUX PWR Fuse #41
Auxiliary Power Outlets
SEO 2 Fuse #42
Roof Beacon and Relay, Full Feature Seat - LH and RH
SEO 1 Fuse #43
Roof Beacon Switch, Cellular Phone Wiring Provisions
DRL Fuse #44
Daytime Running Lamps (DRL)
FOG LPS Fuse #45
RADIO Fuse #46
Radio and Instrument Cluster
CIGAR Fuse #47
Data Link Connector, Cigar Lighter
RT TURN Fuse #48
RH Turn Signals
ATSLC Fuse #49
Automatic Transmission Shift Lock Control Solenoid
LT TURN Fuse #50
LH Turn Signals
FR PRK Fuse #51
Front Park Lamps
W/W Pump Fuse #52
Windsheild Washer Pump
IGN C Fuse #53
Ignition Switch, Crank, IGN 0 Fuses
RDO AMP Fuse #54
Radio/Audio Systems Amplifier
HAZ LP Fuse #55
EXP LPS Fuse #56
HORN Fuse #57
CTSY LP Fuse #58
Inadvertent Power Relay (Courtesy Lamps)
RR WPR Fuse #59
RR Wiper Washer,RR Wiper Motor
TBC Fuse #60
Body Control Module
Let me do a little checking. I thought the relay was "integrated" into the resistor pack.
But if it can be replaced, you will have to measure to make sure that the power is getting to the input of that relay, and is making to the output. If not, you could have a burned trace on the resistor assembly board.
Back soon, Greg A.
I believe the resistor pack should look something like this, where the relay is enclosed inside the "box" I have drawn below.
Is this what you have?
OK. Well if you can hear that relay clicking, then you will actually have to test to see if the power is coming into that relay, from the fuse you said you checked. Then make sure that the power can make it to the output.
What I would do is probe Pin G (should be an orange wire) when the controls are set to High, and the ignition is turned on. You can use a multimeter set on the voltage scale, or a test light, to check for power on that pin.
Then check for power coming out of what should be a purple wire and going to the blower motor. You will need to have power there too. If the current is not making it through that path when the system is switched to High, then there has to be a connection problem with that relay.
Please let me know what you find, or if you need more help.
Take Care, Greg A.
I am in West Coast time, so that shouldn't be a problem.
Just so you know, usually the Resistor modules are sold and replaced as one assembly. I checked on Rockauto.com and found that they cost about $25-$35.
On some of my older vehicles, I have gotten away with replacing relays on the resistor modules, but they don't seem to last very long. I don't think the "generic" relay I put in there could stand the higher current when the motor is on high.
Thanks for letting me know. You may have got a bad module there. It happens some times.
Hi again Tex. Sorry to get back to you so late, but I was out for a late supper with my wife.
It does sound kind of strange. I would think that if the motor runs on the lower speeds, it should run on the high speed setting.
Did you make the measurements on the motor side of the relay with everything still connected? If not, I would reconnect everything and "back-probe" the pin that leads to the motor (red or purple wire - the output side) and watch the voltage for changes between the high setting and the next lower setting that works. If you do that, please let me know what the two voltage readings are (assuming you have a voltmeter).
I would hate for you to replace the motor and then have the same results, but I suppose I have seen stranger things happen. It just doesn't make sense to me that the motor would run at all speeds except high, if the motor is bad.
Another thing you can try is applying power (and ground) directly to the motor connector pins. That would be the same as using the high setting through that relay.
Please let me know what you find.
Next step is to apply power and ground directly to the motor. That means pull the connector to the motor loose, the apply power directly to the motor connector pins. The motor should spin a full speed.
This is starting to get a little baffling. The schmatic does not show that the ground is switched, and your measurements look correct. Strange.