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What can be causing my 2020 honda civic sport to rumble when the lights/ac/ defroster is on at idle and low speeds with both feet off pedals?


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Navarrodavid425
Novice

Sep 18, 2024, 9:17 PM

Post #1 of 6 (865 views)
What can be causing my 2020 honda civic sport to rumble when the lights/ac/ defroster is on at idle and low speeds with both feet off pedals? Sign In

2020 HONDA CIVIC SPORT 2DR COUPE 60K MILES.

**Car Issue: Severe Vibration at Idle with AC, Lights, or Defroster On**

**Symptoms:**
1. **Vibration at Idle:** When the car is in park or on startup, turning on the AC, lights, or defroster causes the idle to kick up, and the car starts vibrating severely. This only happens while the car is stationary. When driving on the highway, there is no noticeable vibration with these features on.

2. **Braking at Stoplights:** When I come to a stop at a red light, the car does not vibrate if the brake is fully pressed. However, once I start releasing the brake, the vibration begins again.

3. **Performance with AC, Lights, and Defroster Off:** The car performs significantly better with the AC, lights, and defroster off, so I’ve been avoiding using them and mainly driving during the day for precaution.

---

**AC System Issue: High Low-Side Pressure & AC Compressor**

1. **High Low-Side Pressure:** The low-side pressure in the AC system spikes into the red zone, but this only happens when the AC compressor is making a strange noise, almost as if the clutch isn’t engaging properly. When the pressure regulates, the noise stops & the fan kicks on.

2. **Compressor Noise:** This compressor noise does not occur 100% of the time. It comes and goes along with the pressure fluctuation.

3. ** I have not experienced any hot air coming out vents at all **

---

**Diagnostic Code:**

Connected a scan tool and found Code B1479 Flow Sensor Circuit. The mechanic suggested replacing the AC compressor and condenser, but I’m confused since the lights and defroster also cause the same vibration issues when the AC is off, to the technicians defense, I did notice that the lights also make the car shake until AFTER he checked it out.

Any help or suggestions before I go ahead with these costly repairs would be greatly.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 19, 2024, 2:20 AM

Post #2 of 6 (855 views)
Re: What can be causing my 2020 honda civic sport to rumble when the lights/ac/ defroster is on at idle and low speeds with both feet off pedals? Sign In

First off, there is no need for duplicate questions. The same people see all the questions.

You could have more than one problem but the main issue of vibration sounds like bad motor mounts.

The issues with the AC may or may not be related but that certainly cannot be diagnosed with the equipment you are using.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Navarrodavid425
Novice

Sep 19, 2024, 11:01 AM

Post #3 of 6 (840 views)
Re: What can be causing my 2020 honda civic sport to rumble when the lights/ac/ defroster is on at idle and low speeds with both feet off pedals? Sign In

Hi thank you for replying, and also, Noted! Sorry for posting more than once. I took the car to Honda for a full diagnostic and heres what came up.. I'll include the pricing because I think they are charging 100%+ mark ups.

I caved and paid for the dealer diagnostic.

Dealer said I need to replace engine side mount assembly (shaking issues) & that the AC compressor overheated, damaged the clutch & coil and must be replaced + charged to max.

Diagnostic: Customer states vehicle is vibrating at idle, upon inspection confirmed harsh vibration at idle, followed diagnostic trouble shooting found engine side mount blown and leaking, pryed on mount and vibration goes away, at this time need to replace ENGINE SIDE MOUNT ASSEMBLY.
$754.14

Customer state ac blowing hot air, found compressor over heated and damaged clutch and coil, need to replace compressor clutch & coil and charge system to max.
$1996.45

*Transmission Service: CHANGE TRANSMISSION FLUID ( SEE ADVISOR FOR PRICE AS IT WILL VARY BY MODEL) DUE BY MILES FOUND FILL PLUG OUT OF PLACE
$179.95

*Brake Flush: BRAKE FLUID SERVICE
$179.95

*Coolant Drain and Refill: COOLANT EXCHANGE REMOVE EXISTING COOLANT, CHECK OPERATION OF ALL COMPONENTS AND REFILL
$174.95

*Drive Belt REPLACE DRIVE BELT
$296.00

*Throttle Body Service: THROTTLE BODY CLEANING/ RESET BASE IDLE WITH HONDA SCAN TOOL, ADD FUEL INJECTION CLEANER TO TANK
$169.95


Windshield Wiper Inserts Replacement: replace both front inserts tom
$24.95


OTHER: replace passenger front fender liner with dips and hardware found damaged.
$487.24

Printed on September 19, 2024

Quote expires on October 19, 2024

Subtotal $4263.58
Shop Charges
Tax
$49.99
$298.45
Total $4612.02


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 19, 2024, 11:12 AM

Post #4 of 6 (838 views)
Re: What can be causing my 2020 honda civic sport to rumble when the lights/ac/ defroster is on at idle and low speeds with both feet off pedals? Sign In

Hahaha............

Those prices are outrageous. They threw in a bunch of random maintenance too. I guess they just need business.

I pretty surprised they only found one mount bad and didn't want to replace all of them.

The AC diagnosis I find a bit confusing. The compressor overheated so they are only changing the clutch? That just doesn't add up to me and I do an awful lot of AC work. It's an electro-magnet clutch. They don't just overheat. I would understand if they said the internal compressor was failing and they need to replace the whole compressor and condenser. That would make more sense to me.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Navarrodavid425
Novice

Sep 19, 2024, 11:19 AM

Post #5 of 6 (835 views)
Re: What can be causing my 2020 honda civic sport to rumble when the lights/ac/ defroster is on at idle and low speeds with both feet off pedals? Sign In

Thank you again for such a quick reply, I have already found most of these parts and total is less than $400. Insane. Also, I asked about that regarding the compressor & condenser. The dealership said that they would be replacing the entire AC Compressor, the clutch & coil is what is gone, so the entire compressor needs to be replaced. However, they said the condenser is fine, which funny enough is the only thing that would be covered under my extended warranty. They had a service bulletin and put out a notice on free ac condenser replacements for broken ones but they said mine is ah-okay and I dont need one.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Sep 19, 2024, 11:34 AM

Post #6 of 6 (833 views)
Re: What can be causing my 2020 honda civic sport to rumble when the lights/ac/ defroster is on at idle and low speeds with both feet off pedals? Sign In

I disagree with them on that.

Compressors and clutches fail due to the compressor starting to bind up internally which causes it to start to come apart internally. When this happens all the debris from the compressor gets pushed into the next component which is the condenser.

Condensers used to be designed as one continuous "serpentine" style where crap could be flushed back out. Now the use a bypass type where one large chamber feeds multiple horizontal tubes so when you force flush through it, it only passes through the clear tubes and does nothing for the clogged tubes. Because of this design you can have 90% of a condenser plugged up and still be able to blow through it.

A plugged condenser will not completely condense the hot gas back to a warm liquid. The causes less cooling and higher head pressures which leads to early compressor failure and even further blockage of the condenser.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







 
 
 






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