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Hvac fan only works on the 2 high speeds 4 & 5?

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  • Chevrolet Master
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The resistor pack for the blower motor needs to be replaced. It is located behind the glovebox.

Posted on Sep 25, 2010

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My suzuki alto stantard SZ 5 DOOR 2012 modle heating is now working Please advise


HVAC, the heater is not working?
the resistor only makes fan work , on low speeds.
1: is the fan blowing? heard and felt? on HIGH?
2: is engine coolant at 180F temp, or more holding, IT must, or there will not be heat,.
3: are both fire wall heater core hoses hot, fully? if one is cold the core is blocked. (flush it out)
4: Ok, we have hot water coolant to core (heater core) so is the damper open?, yes, then now you have heat for sure.

if all that is greek , get car serviced.
or buy the FSM book read , HVAC chapter
the factory service manual







Jan 18, 2015 | Suzuki Cars & Trucks

2 Answers

How do I check my fan switch air cond. blower motor?


2014 post.? old post, its DC motor NOT A.c.
direct current, not alternating current motor.
no need to guess, use a voltmeter, and save lots of cash, for sure..... a $10 voltmeter works,.

first off there are 2 systems. manual and auto
which is it? (options day 1)
on this car you scan it, first. it has DTC errors
not to be ignored, if present.


let me answer for all car HVAC car owners.
it can be many things.
1: fuses blow (dead fan)
2: wires bad, cut, or melted or corroded (weak fan)
3: controller is bad.
4: the dampers not open fully.
5: if HVAC has fan resistor it can fail on low speeds but not high. (or fail only on high)
6: if the fuse on the left below is blown there will be no high speed, Fuse #35 blown. no high.

note how this unique car runs a relay just for high. see drawing below.ff37835b-9047-4b0d-91e8-44f56ef6ba66.jpg

for sure the motor is last.
the fan can be hot wired, before removal
if passes that test its GOOD.
what matters is 12vdc (13.3 to 15v engine running)
to the fan.
and if only one speed fails, and not high say so
or if only high speed fails, say so.
as that set of symptoms is never a fan.
for sure if it runs ok on high.,
so fuses first.'
then the relay if high fail.s.

Sep 23, 2014 | 2005 Isuzu Ascender

2 Answers

My fan blower will not work on high speed on my chevy 2005 silverado


if you got heat on all speeds and the blower motor is working properly then you probably need a new HVAC switch.

Jan 19, 2013 | 2005 Chevrolet Silverado

1 Answer

Blower stays on after key is removed, now a/c works in front once I hit the highway.


Which of these systems does your vehicle have ?
HVAC Systems - Automatic
Blower Motor Control Processor
The blower motor control processor controls the speed of the blower motor by increasing or decreasing the voltage drop on the ground side of the blower motor. The HVAC control module provides a voltage signal to the blower motor control processor over the blower motor speed control circuit. As the requested blower speed increases, the HVAC control module increases the amount of time that the speed signal is modulated to ground. As the requested blower speed decreases, the HVAC control module decreases the amount of time that the signal is modulated to ground.

HVAC Systems - Manual
Air Speed - Front Control
The blower motor forces outside air into the vehicle's interior. The vehicle operator determines the blower motor's speed when the driver places the blower switch in one of 5 blower speeds. The blower motor will always operate in any switch position other than OFF, as long as the ignition switch is in the RUN position. The blower motor and mode switches are located within the HVAC control module. The blower motor OFF input is connected in series with the HVAC control module by the off blower motor control circuit.
Depending upon the selected speed, power is provided to the blower motor from either the ignition 3 voltage or battery positive voltage circuits from the fuse block. The battery positive voltage circuit only provides power when the High blower switch position is selected. Power and ground are provided to the HVAC control module by the ignition 3 voltage and the ground circuits.
Low Blower Speed
When the Low 1 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the low blower motor control circuit. Voltage is divided between 4 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
Medium Blower Speeds
When the Medium 1 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 1 blower motor control circuit. Voltage is divided between 3 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
When the Medium 2 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 2 blower motor control circuit. Voltage is divided between 2 series resistors, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
When the Medium 3 blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the medium 3 blower motor control circuit. Voltage is divided between a series resistor, a blower relay, and the blower motor to achieve the desired blower speed. The blower motor is grounded through the ground circuit.
High Blower Speed
When the High blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly through the high blower motor control circuit. The voltage energizes the blower relay, causing the blower motor to be connected directly to the battery positive voltage circuit. The blower motor and blower motor relay are grounded through the ground circuit.

HVAC Control Module
The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The body control module (BCM), which is the vehicle mode master, provides a device on signal. The control module supports the following features:

Feb 09, 2018 | 2005 Chevrolet Tahoe

1 Answer

HVAC blower motor only works on 4 & 5 high speed settings. Fuss?


Most likely it is the controls not a fuse. A bad fuse would not let the blower work at all.

Mar 05, 2011 | 1999 Oldsmobile Cutlass

1 Answer

2005 Jeep Grand Cherokee. Htr/AC fan switch only functions @ highest speed. At lower speed settings I can hear doors opening and closing---but not air.


replace the blower motor resistor. It controls the fan speeds. It defaults to high speed only when it fails.

How to replace the blower motor resistor block: Caution: Stay clear of the blower motor and resistor block (Hot). Do not operate the blower motor with the resistor block removed. 1. Disconnect and isolate the battery negative cable.
2. Remove the glove box from the instrument panel.
3. Pull out the lock on the blower motor resistor wire harness connector to unlock the connector latch.
4. Depress the latch on the blower motor resistor wire harness connector and disconnect the connector from the resistor.
5. Remove the two screws that secure the blower motor resistor block to the HVAC housing.
6. Remove the resistor block from the HVAC housing. Installation:
1. Position the blower motor resistor block into the HVAC housing.
2. Install the two screws that secure the resistor block to the HVAC housing. Tighten the screws to 2.2 Nm (20 in. lbs.)
3. Connect the wire harness connector to the resistor block.
4. Push in the lock on the blower motor resistor wire harness connecgtor to lock the connector latch.
5. Install the glove box.
6. Reconnect the battery negative cable.
7. Have a nice day!

Oct 11, 2010 | Jeep Cherokee Cars & Trucks

1 Answer

2006 GMC Envoy I6 HVAC fan stopped working. Level 5 stopped about 6-months ago and now it doesn't work at all. I checked all fuses and the cooling fan relay but still not working.


If high speed went out first, then it is the switch.
There is the most arcing in the switch at high speed.
If there was motor or relay trouble, it would effect all speeds.
If there were problems with the ballast resistor, it would effect lower speeds.

Aug 07, 2010 | 2006 GMC Envoy

1 Answer

Fan only works on 4 and 5 settings? Is this a


Hello,

I have a 2003 Chevy Cavalier. The HVAC airflow dial only works on high setting. We checked the fuse and it's o.k.

What now?  Any estimate as to repair cost? 

Thank you

Sep 07, 2009 | Chevrolet Malibu Cars & Trucks

1 Answer

Blower fan only works on high


CHECK THE HVAC CTRL FUSE.

WITH A TEST LIGHT CHECK THE BLOWER RESISTOR FOR POWER ON THE YELLOW, TAN, PURPLE, AND LIGHT BLUE WIRES. THE ORANGE WIRES CONTROL THE HIGH SPEED CIRCUIT. DO THIS FOR EACH POSITION OF THE BLOWER SWITCH.

THE BROWN WIRE ON THE HVAC CONTROL CONNECTOR 1 POSITION B COMES FROM THE HVAC FUSE 20 AMP. NO POWER ON THAT WIRE WILL CAUSE THE BLOWER TO NOT FUNCTION ON THE LOWER SPEEDS.

Jul 14, 2009 | 2000 Pontiac Grand Prix

1 Answer

Only have 1 speed on HVAC fan


the fan relay(resister) that control fan speed is probably burned out.When this occurs it will only blow at high speed because its getting 12volts directly to the fan

May 25, 2009 | 2004 Pontiac Vibe

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