Climate control panel (HVAC) is not working why?

Tiny
BRUCE YARNELL
  • MEMBER
  • 2014 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 70,000 MILES
Have no lights on the climate control panel and it's not working no fan or heat or A/C.
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Tuesday, April 2nd, 2019 AT 11:34 PM

61 Replies

Tiny
JOETECHPRO
  • EXPERT
Hey Bruce Yarnell,

Do you have automatic climate control ag. can you set the temperature?
Or do you have manual A/C, no specific temperature control?

You have nothing from the controls at all?

The first check would be to check fuses.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Please check all fuses in the under hood fuse box.

From the diagrams fuses 17,39,48,55,60,70 are for the HVAC

Most likely the power to the control unit is fuse 39, this would cause the panel to completely no function.

Hope this helps.

Regards, Joe
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Wednesday, April 3rd, 2019 AT 10:54 AM
Tiny
BRUCE YARNELL
  • MEMBER
Manual ac and no power at all to control, checked fuses but will recheck.
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Wednesday, April 3rd, 2019 AT 1:18 PM
Tiny
BRUCE YARNELL
  • MEMBER
Pulled these codes today from the BCM:
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Wednesday, April 3rd, 2019 AT 1:21 PM
Tiny
JOETECHPRO
  • EXPERT
Hey Bruce Yarnell,

I have attached the wiring diagram below.

This is different from the diagram I was originally looking at.

The fuses are in the fuse panel on the left end of the dash.

Fuses 22 and 26.

22 is live with ignition on
26 is always live/constant feed

If fuses have power and are intact then you will nee to access the HVAC control module to check If you have power and ground there.

The HVAC control module is situated behind the glove box, it is remote from the dash controls.

If you do have power and ground but the unit is still not working you will need to replace the HVAC module.

Regards, Joe
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Wednesday, April 3rd, 2019 AT 3:17 PM
Tiny
JOETECHPRO
  • EXPERT
Hey Bruce Yarnell,

If you need to check the power/ground at the HVAC control module.

When you remove the upper glove box you should see the HVAC module behind.

It has 4 connectors.

The Power/ground is in the 2nd connector.
Pin 8 black/white is the ground
Pin 1 red/violet is permanent 12V
Pin 9 violet/grey is ignition 12V

With the unit plugged in back probe using pin 8 as your ground, ignition on, check what you have on pins 8 and 9. You should have 12V, If you do then the A/C control module should be communicating. I would advise replacing the module.

You will need to reprogram the new module to the vehicle order, you will need a scanner with this function.

If you do not have 12V move your black lead from pin 8 and put it on a known good ground.

If you now have 12V then you have a ground issue.

If you don't have 12V power supply wiring issue.

Hope that helps.

Regards, Joe
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Wednesday, April 3rd, 2019 AT 4:07 PM
Tiny
WYLLOW
  • MEMBER
  • 2008 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 96,000 MILES
Lost control of mode and temperature. Fan control works fine. Replaced just the blend actuator. Worked for a few days, now back to no control of temperature or position. This is a manual control system.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
KEN
  • ADMIN
Hello,

This sounds like the HVAC control head has stopped working but to confirm the failure letting make sure it is getting power and ground.

Here is a guide and some diagrams to help you run some easy tests:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Here are some wiring and fuse panel diagrams along with the blend door actuator locations in case you need them. Check to see if the panel is getting power after checking the HVAC fuse. There are four fuses that run the system as you can see from the wiring diagram.

Check out the diagrams (below).

Let us know what happens and please upload pictures or videos of the problem.

Cheers, Ken
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
DREW MATTHEWS
  • MEMBER
  • 2006 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 97,000 MILES
Although the climate control buttons light up, none of them function. The display is permanently dark and climate control does not function whatsoever.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

I attached the wiring diagram and the connector diagram for you of the unit.

There are 3 powers to the control that must be verified. There are 2 fuses that feed power to the unit.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Let me know when you are ready to do some testing.

Roy
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
BBORTNER21@GMAIL.COM
  • MEMBER
  • 2005 CHEVROLET SILVERADO
  • 6.6L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 300,000 MILES
My dash lights will dim and or go out all together, then come back on. All the gauges always work and it does not effect my driving lights (outside of vehicle). Sometimes playing with the dash light brightness control will bring them back on. This also effects the radio lights too, yet the radio still works. My biggest issue is the temperature control, many times it will be dark and you can not control it at all. When it does come back on many times it will be at 60 degrees like it has reset or something. My air also is impacted and doesn't always work (blowing warm air), yet other times it works just fine. This morning on the way to work the dash lights were flickering and then all came on and worked fine. Any thoughts?
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
STEVE W.
  • EXPERT
Okay, that sounds more like an internal solder joint issue. Not uncommon after most companies switched away from lead based solder. The high tin stuff loves to fail. Do you notice it being better or worse if the temperature changes and causes the board to flex?
You could pull the init out and check the connections to it, It's very easy but don't do it when it is very cold, the entire trim panel just pulls off and if it's cold it can be more easily broken.
You tilt the steering wheel down as far as it will go, then gently start at one side and pull the panel off, there are multiple clips that hold it to the dash. Once it is off the control head comes off with 2 screws and clips.
One thing to do if you disconnect it would be that it needs to be calibrated. For this you simply re-install the parts, then remove the HVAC/ECAS fuse for 20 - 30 seconds. Re-install the fuse and start the truck. Don't touch the controls, the unit will re-calibrate in about a minute. You do this same thing if you put a replacement control unit in, just be sure the replacement matches the options your truck has.
It is possible to test the system further but it requires a scan tool to do much of it.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
ENGINEERFRED1
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • 6.6L
  • V8
  • TURBO
  • 4WD
  • AUTOMATIC
  • 119,000 MILES
Had recently replaced control panel and had A/C serviced was working great. Last night was working fine when the panel went out and A/C stopped working no fan or controls. But I can tell the A/C compressor is still working or coming on. Checked fuses but they all checked out okay.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good morning,

I attached a wiring diagram for you of the fuses as well as the control for power.

https://www.2carpros.com/articles/how-to-check-wiring

Check the fuses for power on both sides. This is not a visual test, it is a power test.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check the pins I circled at the control unit. If you have power then the control unit is the failure.

Roy

1. Remove the instrument panel accessory trim plate.
2. Remove the screws from the HVAC control module.
3. Depress the control assembly retaining tabs and remove the HVAC control module from the instrument panel.
4. Disconnect the electrical connectors from the HVAC control module.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
TAWAS23
  • MEMBER
  • 2003 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 125,000 MILES
Having trouble finding out why my manual climate controller has no power only blower motor works. The rest is out pressing buttons on A/C nothing defrost nothing. Upper/lower circulating button nothing. Fuses checked inside HVAC 1 good and heater/A/C good. Engine area fuse block checked havac/ecas good. Please point me in a good direction also replaced in dash havac controller nothing.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
KASEKENNY1
  • EXPERT
Hi,

That is great that you checked these fuses. However, the HVAC/ECAS is the one that gives power to the controls. The HVAC 1 is your ignition feed which needs to operate as well so that is good that these fuses are intact, but we need to make sure we actually have power going through them.

If we have power on the load side of the fuse but we do not have power at the component, then you have a wiring issue. I would go to the back of the HVAC control module in the dash and see what voltage you have coming in on the orange wire. By what you are saying it sounds like you don't have power. If this is the case, I would just run a new wire from the fuse to the module. I would just cut the wire about 3 inches from each end and splice in a new wire and then retest it.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
TAWAS23
  • MEMBER
Okay, sounds great, thank you, I will test first thing tomorrow that really helps I appreciate it.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
KASEKENNY1
  • EXPERT
You are welcome. Please let me know what you find. Thanks for using 2CarPros.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
CHASE6142001
  • MEMBER
  • 1991 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 253,000 MILES
The heater control on my truck just stopped working. The button lights come on when I flip truck lights on but screen is blank. I've replaced the relays, blower motor, resistor, control panel, and checked fuse everything is good. I've changed the plugs where they have melted but I cannot find the problem.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
TAWAS23
  • MEMBER
Okay, wanted to get back to you. I checked my power wires as the diagram you sent me and have no power to orange wire B7 highlighted. So should I run power to that just orange B7 wire like you stated? Also no power to orange wire on blower side either but fan does work. Both plugs have power to brown wires ignition 3 fuse. Thanks for the help.
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Friday, April 30th, 2021 AT 4:13 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

By any chance, did you have the battery disconnected recently? Take a look at this TSB.

1991 Chevy Truck K 1500 Truck 4WD V8-350 5.7L
HVAC Control Head - Inoperative, No Display
Vehicle Heating and Air Conditioning Control Assembly Technical Service Bulletins HVAC Control Head - Inoperative, No Display
HVAC CONTROL HEAD - INOPERATIVE, NO DISPLAY
Number: 93-44-1A
Section: 1A
Date: NOV. 1992
Corporate Bulletin No.: 261210
ASE No.: A7

Subject:
HEATER VENTILATION AIR CONDITIONING (HVAC) CONTROL HEAD INOPERATIVE - NO DISPLAY

Model and Year:
1990-93 C/K TRUCKS

The HVAC control head on some 1990-93 model year C/K trucks may not illuminate when the vehicle is first started. This condition is much more likely to occur after a battery disconnect or control head replacement but may occur after any ignition cycle.

The condition is not permanent, it stems from the control head not receiving a correct signal when the ignition is turned on.

Recycling the ignition switch may bring the control head back to normal operation. If cycling the ignition does not work, disconnect and reconnect the battery making sure that a good electrical connection is maintained when reconnecting (avoid "chattering" the battery line).
_________________________

If that isn't the case, I need you to check for power to the control head. See pic 3 for the power supply. Also, pics 1 and 2 are relevant to the power supply (fuse). Reconfirm the fuse is good. If it is, confirm there is power in and out of the fuse.

______________________

Here are a few links you may find helpful:

https://www.2carpros.com/articles/how-a-car-fuse-works

https://www.2carpros.com/articles/how-to-check-a-car-fuse

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

_______________________

Let me know what you find.
Joe
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Friday, April 30th, 2021 AT 4:13 PM (Merged)

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