AC and Heater Issues Honda Civic 06


Asked by Guru6HS1T Mar 22, 2020 at 06:23 PM about the 2006 Honda Civic

Question type: Maintenance & Repair

Hey Everyone!

Trying to diagnose what the issue really is. My mechanic wants me to spend
$150 for an AC specialist to come in for diagnosis...Rather not spend that if I
don't have to

When driving the AC will be working fine and then when accelerating
sometimes heat comes out of it. When I turn the heat on while driving cold air
can come out of it.
When the car is idle and i turn the AC on the lowest setting the clutch spins
fine and turns off every so often for a few seconds before turning back on.
When in MAX AC mode it keeps spinning without issue. Same for when the
heat is on. The problem usually is only when driving.

How would you continue to check for diagnosis issues?
Relay switches?
Front head gasket issue?

The car doesn't overheat when driving. No issues there.

5 Answers


Sounds like the system is losing vacuum do to a bad vacuum check valve. Intake manifold vacuum is highest at idle. As you accelerate the vacuum decreases. A check valve is put in the system to hold vacuum under these conditions to prevent temperature door shifting and mode shifting. Some systems also have a vacuum reserve tank in the system too. The operation of the compressor sounds normal. At low blower speed less coldness is being pulled out of the refrigeration system. This allows the pressure to drop, on the low side of the system, to the cut out point and the compressor stops for a few minutes to prevent the system from freezing up. Hope that helps! Jim


Thank you for your input. How would one test for this? I tried googling, but come up with other results that I don't think are correct.

1 people found this helpful.

You're welcome. Glad to help. Look for a check valve in the vacuum hose going from the engine to the firewall. It'll be a little round disk like thing. The vacuum reserve tank, if equipped, will look like a square black box, or possibly a round plastic ball. It will have two vacuum hoses hooked up to it! Hope that helps! Jim


How would one know if it actually is the cause of the problem? Replace it? Is there another way to see if the valve is working appropriately?

1 people found this helpful.

The check valve is cheap enough that you can just replace it. It's like a $3.00 part. Hope that helps! Jim

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