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Fan speed wont change speeds on heat or cold cycles

I turn the heat or AC on and the fan blows at low speed. the heat or cool that comes out is as it should be just not enough fan to distribute everything.

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  • Cars & Trucks Master
  • 467 Answers

Sounds like the Blower Motor Resistor. The range from 10 to 75 dollars depending on what kind of vehicle. Pretty easy to change.
Blower Motor Resistor Repair Heater Fan Speed Control Chevy Blazer GMC...

Posted on Nov 10, 2014

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6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

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jigsaw_9077
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SOURCE: 1998 BMW 328i heater/AC blower is not running

You have clean the blower unit , may be its dirty then . and then check the blower resistor unit for malfunction.

Posted on Aug 04, 2009

  • 15 Answers

SOURCE: ac does not blow cold at idle... ac condenser fan

that seems to be the problem. If the fan does not turn on when the a/c is turned on it could be a fuse, relay, control box, or just a bad fan. Try connecting the fan directly to see if it works. Does this car have 2 fans? normally all the small cars have 2 fans one for the engine cooling and one to assist the first when the a/c is turned on. Without the fan pulling air through the a/c condensor the had pressure goes up high enough to shut off the a/c compressor. It also causes some cars to run warmer than usual when stopped. Check the a/c condensor for blockage also which doesn't have anything to do with your fan not working.

Posted on Aug 18, 2009

  • 20 Answers

SOURCE: The AC blows on #4 fan setting but doesn't blow at all on 1-3

That is the blower resistor. 4 is wide open, so, no resistance. I had 4 of them put into my truck. The wires were burnt and shorted the others until the problem was found. Check the plug if you do this yourself.

Posted on Sep 04, 2009

  • 10 Answers

SOURCE: How to fix 1999 lincoln TC heater/AC fan speed.

You have a problem with the resistors on your blower motor. 95% of AC/Heater blower motors are located under the glove box in the passanger foot well. When you remove the motor you should see a resistor plate. Resistors are not servicable and will need to be replaced. This is a relatively cheap part, that you can replace yourself if your handy, if not take it to your local tech.

Posted on Nov 13, 2009

  • 229 Answers

SOURCE: 1999 lexus rx300. fan won't blow. ac light is on

Possibly the connector to the blower unit has been diconnected or is loose.

Posted on Apr 22, 2010

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I have a 2006 buick lucerne 3.8 v6 cxl.my coolinf fans dont come on .i need to know how to change the relay and the fuse.


Your vehicle cooling fan's are controlled by three relay's , couple of fuse's an the PCM - engine computer . The engine coolant temp. sensor is a input to the PCM , when engine temp get's to 212 the PCM will turn on the cooling fans in low speed . Checking to see what the actual temp is with a scan tool an a infrared thermometer at the thermostat housing ,an looking up the specification's in a service repair manual is how to diagnose . Not guessing an replacing parts . Plus learning how the cooling fan's work .
Relay Driven Dual Cooling Fan Diagnostics Reading factory service info as to how they work also would be a good idea .

Cooling Fan Control - Two Fan System
The engine cooling fan system consists of 2 puller type electrical cooling fans and 3 fan relays. The relays are arranged in a series parallel (S/P) configuration that allows the engine control module (ECM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block. The ground path is provided at G104.
During low speed operation, the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan S/P relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the ECM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the ECM supplies a ground path for the high speed fan relay and the cooling fan S/P relay through the high speed cooling fan relay control circuit. This energizes the cooling fan S/P relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time, the high speed fan relay coil is energized closing the relay contacts, and provides battery positive voltage from the high fan fuse on the cooling fan motor supply voltage circuit, to the right cooling fan. During high speed fan operation, both engine cooling fans have their own ground path. The result is a parallel circuit with both fans running at high speed.
The ECM commands the low speed cooling fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 94.5°C (202°F).
• A/C refrigerant pressure exceeds 1447 kPa (210 psi).
• After the vehicle is shut OFF, if the engine coolant temperature at key-off is greater than 101°C (214°F), the low speed fans will run for a minimum of 60 seconds. After 60 seconds, if the coolant temperature drops below 101°C (214°F), the fans will shut OFF. The fans will automatically shut OFF after 3 minutes, regardless of coolant temperature.
The ECM commands the high speed fans ON under the following conditions:
• Engine coolant temperature exceeds approximately 104.25°C (220°F).
• A/C refrigerant pressure exceeds approximately 1824 kPa (265 psi).
• When certain DTCs set
At idle and very low vehicle speeds the cooling fans are only allowed to increase in speed, if required. This ensures idle stability by preventing the fans from cycling between high and low speed.

Dec 10, 2017 | Buick Cars & Trucks

2 Answers

I have 2007 Suzuki XL7. I replaced radiator and fan assembly. Fans do not work. Is there a relay? If so, where is it?


Most fan and Ac relays are located in the under hood fuse and relay box. Adequately marked in owners manual or on plastic cover

Sep 03, 2016 | Suzuki XL7 Cars & Trucks

1 Answer

2007 ford taurus condensor fan not coming on with ac


Fan Control The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C on/off status, A/C pressure) to determine engine cooling fan needs.
For variable speed electric fan(s):
The PCM controls the fan speed and operation using a duty cycle output on the fan control variable (FCV) circuit. The fan controller (located at or integral to the engine cooling fan assembly) receives the FCV command and operates the cooling fan at the speed requested (by varying the power applied to the fan motor).


EDGE/MKX, FIVE HUNDRED/FREESTYLE/MONTEGO, FUSION/MILAN/MKZ, CROWN VICTORIA/GRAND MARQUIS, TOWN CAR: FCV DUTY CYCLE OUTPUT FROM PCM (negative duty cycle) FCV Duty Cycle Command (NEGATIVE (-) duty cycle) Cooling Fan Response/Speed Greater than 0 but less than 5% Fan off, controller inactive Greater than 5% but less than 10% Fan off, controller is in active/ready state Edge/MKX, Crown Victoria/Grand Marquis, Town Car:
10% - 90% Edge/MKX, Crown Victoria/Grand Marquis, Town Car:
Linear speed increase from 30% to 100% Five Hundred/Freestyle/Montego, Fusion/Milan/MKZ:
30% - 90% Five Hundred/Freestyle/Montego, Fusion/Milan/MKZ:
Linear speed increase from 50% to 100% Greater than 90% but less than 95% 100% Greater than 95% but less than 100% Fan off
For relay controlled fans:
The PCM controls the fan operation through the fan control (FC) (single speed fan applications), low fan control (LFC), medium fan control (MFC), and/or high fan control (HFC) outputs. Some applications will have the xFC circuit wired to 2 separate relays.
For 3-speed fans, although the PCM output circuits are called low, medium, and high fan control (FC), cooling fan speed is controlled by a combination of these outputs. Refer to the following table.
If you don't understand these thing's listed above your best bet is to take your vehicle to a qualified repair shop . Have the vehicle checked for DTC'S - diagnostic trouble codes !
If

Jun 14, 2016 | Ford Cars & Trucks

1 Answer

Engine cold. Start engine reading says engine hot ac off. Fans run all time.


Are the fans running on low or high ?
Circuit/System Description
The engine control module (ECM) commands the fans ON in either high speed or low speed, depending on cooling requirements. In low speed, both fans are turned ON at a reduced speed. High speed has both fans turned ON at full speed.
In low speed operation, the ECM applies ground to the coil side of the fan low relay. This energizes the coil and applies voltage directly to the left cooling fan through the switch side of the fan low relay, which is fed by the fan 1 fuse. The right fan is connected in series to the left fan through the de-energized fan control relay so that both operate at low speed.
In high speed operation, the ECM applies a ground to the coil side of the fan low relay, the fan control relay , and the fan high relay. On the fan high relay, the energized coil closes the switch side of the relay and applies voltage directly to the right cooling fan through the switch side of the relay, which is fed by the fan 2 fuse. At the same time, the ECM energizes fan control relay pulling the switch side over, providing a direct path to ground for the left cooling fan, which has voltage applied through the energized fan low relay. In high speed mode, the fans are operated as a parallel circuit with full voltage applied to each.
You should have it hooked up to a scan tool that can read engine sensor data parameters . Check for DTC'S - diagnostic trouble codes etc...
Circuit/System Verification
  1. If DTCs P0480 or P0481 are set, perform those diagnostics first.
  2. Ignition ON, verify with a scan tool that the control module is not commanding fan activation.
  3. Ignition ON, observe that the fans are not activated.
Your best bet is to take it to a ASE certified repair shop !

Jan 10, 2016 | 2009 Chevrolet Silverado 1500

1 Answer

My ac is not working I have a Chevy Tahoe 2005 the fans won't turn on either .


Hi Maria , The A/C system wouldn't keep the fans from running but none working cooling fans will keep the A/C from working ! This is a fairly complex system if your not familiar with this sort of thing ! I will add the description from the factory service manual.
Cooling Fan Control - Two Fan System
The engine cooling fan system consists of 2 electrical cooling fans and 3 fan relays. The relays are arranged in a series/parallel configuration that allows the powertrain control module (PCM) to operate both fans together at low or high speeds. The cooling fans and fan relays receive battery positive voltage from the underhood fuse block.
During low speed operation, the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. This energizes the low speed fan relay coil, closes the relay contacts, and supplies battery positive voltage from the low fan fuse through the cooling fan motor supply voltage circuit to the left cooling fan. The ground path for the left cooling fan is through the cooling fan s/p relay and the right cooling fan. The result is a series circuit with both fans running at low speed.
During high speed operation the PCM supplies the ground path for the low speed fan relay through the low speed cooling fan relay control circuit. After a 3 second delay, the PCM supplies a ground path for the high speed fan relay and the cooling fan s/p relay through the high speed cooling fan relay control circuit. This energizes the cooling fan s/p relay coil, closes the relay contacts, and provides a ground path for the left cooling fan. At the same time the high speed fan relay coil is energized closing the relay contacts and provides battery positive voltage from the high fan fuse on the cooling fan motor supply voltage circuit to the right cooling fan. During high speed fan operation, both engine cooling fans have there own ground path. The result is a parallel circuit with both fans running at high speed.
Do you have a check engine light lit ? The thing to do would have it check at the dealer or a ASE certified repair facility ! They could hook up a advanced scan tool an diagnose fairly quick ! Or you could find a wiring diagram an try testing with a volt meter yourself ! But watch yourself so you don't short out the PCM - engine computer !

May 01, 2015 | AC Cars & Trucks

1 Answer

Citroen troubleshooting


I had similar problems 2 times with the automatic heat / AC module.
I suppose your system is automatic too.

First time the commands were working erratically acting weird. Sometimes was heating at full capacity blowing heads off. At other times it was not starting at all.
The whole module had to be replaced.

Second time if the car stayed in the sun the AC was heating, after starting the engine and cooling started only after achieving greater speeds (above ~60km/h). Whenever the speed decreased the system began to heat again eventually. It turned out that the engine cooling fan was broken and had to be replaced. That fan cools both the engine radiator and the AC radiator. If it is faulty your engine might be at risk of overheating at low speeds.

Mar 26, 2014 | 2001 Citroen Xsara

1 Answer

05 vue ac problem, ac not cold at idle, blows cold while driving, had checked freon is full, expansion valve was replaced, because high side flutters and low side does same. seems that compressor doesnot...


Hello, Are the cooling fan(s) coming on with the truck in park and the engine at idle? If the cooling fan(s) are not working A/C will not cool with truck setting still.

Oct 02, 2010 | 2005 Saturn VUE

2 Answers

1999 Alero: where is the a/c control tempature :problem is wh...


WELL TURN ON AC MAX COLD HIGH TO SEE IF COOLANT FANS TURN ON.IF NOT YOUR REFRIGERANT SO LOW THAT THE AC REFRIGERANT PRESSURE SENSOR WONT CLOSE CIRCUIT TO TURN ON COOLING FANS.MEANING YOU NEED HAVE AC CHECKED AND CHARGED.ALSO CHECK COMPRESSOR FOR POWER IF NOT YOU HAVE BLOWED FUSE OR BAD RELAY.IF FUSE AND RELAY GOOD YOUR AC COMPRESSOR CLUTCH COIL OPEN OR THE AC CONTROL SWITCH IS BAD.IF COMPRESSOR IS RUNNING WHEN YOU TURN ON AC YOUR AIR TEMPERATURE ACTUATOR NOT WORKING.

May 17, 2010 | 1999 Oldsmobile Alero

3 Answers

My sc1 over heats when at idle and only if ac or heat is turned off as soon as i turn onn ac heat drops imediately


you may want to check on the radiator fan. The AC has its own fan and once AC is on, the fan would help bring down the temperature. It is either the fan is not blowing or has become weak. You can check on the fan by pulling out the temp sensor on the lower radiator hose. The fan should blow at full speed when doing this.

Check on the water reserve the water inside it goes down, if not there may be a leak somewhere. Water vapor may be escaping and lessening the effectiveness of the cooling system. This may be a reason why the engine cools down after the AC fan is on.

Jun 16, 2009 | 1995 Saturn Sc

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