Loud bang when switching between vent modes... - Page 2 - ZR-1 Net Registry Forums

DRM500RUBYZR-1 · 01-07-2017

IF:
Nothing has been disturbed or come loose, and is being buffeted by airflow,
then; there are only really two movable features within the system.

1- the diverter valve and actuator- this does exactly as it sounds like it would, i.e. it diverts the airflow to the outlets invoked by the selection made through the control head, then said selection is passed to the programmer to execute the command, then on to the actuator and the valve, which then re-directs the air.

2- the blend door aka the air mix door- again does what it says, i.e. mixes the ambient air with heated or cooled air to deliver it and achieve the temperature requested at the control head. Temp selection is made at the control head, then communicated through the programmer, which instructs the blend door actuator to move the door to a position that will yield the best mix of air to obtain and maintain the selected temp.

You must determine which sequence is in process when you hear the noise.

I suspect the blend door actuator.

When the car is first started, the system cycles the blend door from fully closed to fully open, one time.
This process conveys info back to the programmer so that ot knows the travel possibilities of the door aiding in determining the soon to be requested commands.

It would seem to be either sticking, or unable to hold itself open, and slamming shut, which although it can operate, it does not have enough strength to hold the door fully open.

While I am sure there are electronic testing procedures in the FSM, it would be far more valuable for you to evaluate the operation of both variables of each system, and determine what is requested immediately before you hear the noise.

Hope I have helped.

Marty

billschroeder5842 · 01-07-2017

Quote:

Originally Posted by MickeyD

My black 90 does that. Only has 2200 miles. I wouldn't worry about it.

I would tend to agree. The loud noise (while disconcerting) actually means the system is fully functional, confident and "positive" in its execution.

An aggressive, positive transmission shift will have a "bang" as well.

henryr · 01-08-2017

ditto

scares the crap out of me every time

Hog · 01-09-2017

Quote:

Originally Posted by rush91

I've noticed this ever since I've had the car. A loud bang / thump / pop whenever I switch between vent modes. And doesn't matter if I'm using the A/C or heat. But for instance if the unit is set on the floor vents, and I hit the button for the dash vents, there is a VERY loud bang....Like something is hitting the underside of the dash. It only happens when I hit the button for the dash vents, or the dash/floor vent combo button. I haven't really dug into this yet, as I hardly use the A/C or heat, which both work fine. The unit works fine, all vents blow out hot or cold air.

Does the "bang" seem louder the higher the fan speed is selected?

GOLDCYLON · 01-09-2017

Its the blend door slapping

Hog · 01-11-2017

Quote:

Originally Posted by GOLDCYLON

Its the blend door slapping

This happens on a few GM vehicles.

geezer · 05-07-2017

I was having the same HVAC 'bang' issue as Rush 91 initially described. HVAC system operated normally in all modes but when first activated experienced the load ,BANG,.
I removed the knee bolsters Drver side & Pass. side to check HVAC vacuum system.
On pass. side found the "orange" vacuum line to the recirculation outside air control pot
had been the victim of 'mickey or minnie'. Sealed the chewed area. 'Bang' issue resolved!!

01-07-2017	#11
DRM500RUBYZR-1 Join Date: Sep 2008 Location: Mullica Hill, New Jersey Posts: 2,566	Re: Loud bang when switching between vent modes... IF: Nothing has been disturbed or come loose, and is being buffeted by airflow, then; there are only really two movable features within the system. 1- the diverter valve and actuator- this does exactly as it sounds like it would, i.e. it diverts the airflow to the outlets invoked by the selection made through the control head, then said selection is passed to the programmer to execute the command, then on to the actuator and the valve, which then re-directs the air. 2- the blend door aka the air mix door- again does what it says, i.e. mixes the ambient air with heated or cooled air to deliver it and achieve the temperature requested at the control head. Temp selection is made at the control head, then communicated through the programmer, which instructs the blend door actuator to move the door to a position that will yield the best mix of air to obtain and maintain the selected temp. You must determine which sequence is in process when you hear the noise. I suspect the blend door actuator. When the car is first started, the system cycles the blend door from fully closed to fully open, one time. This process conveys info back to the programmer so that ot knows the travel possibilities of the door aiding in determining the soon to be requested commands. It would seem to be either sticking, or unable to hold itself open, and slamming shut, which although it can operate, it does not have enough strength to hold the door fully open. While I am sure there are electronic testing procedures in the FSM, it would be far more valuable for you to evaluate the operation of both variables of each system, and determine what is requested immediately before you hear the noise. Hope I have helped. Marty Last edited by DRM500RUBYZR-1; 01-07-2017 at 09:52 AM. Reason: grammer

01-08-2017	#13
henryr Join Date: Sep 2016 Location: Atlanta Posts: 93	Re: Loud bang when switching between vent modes... ditto scares the crap out of me every time

01-09-2017	#15
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,153	Re: Loud bang when switching between vent modes... Its the blend door slapping __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

05-07-2017	#17
geezer Join Date: Aug 2010 Location: ottawa canada Posts: 155	Re: Loud bang when switching between vent modes... I was having the same HVAC 'bang' issue as Rush 91 initially described. HVAC system operated normally in all modes but when first activated experienced the load ,BANG,. I removed the knee bolsters Drver side & Pass. side to check HVAC vacuum system. On pass. side found the "orange" vacuum line to the recirculation outside air control pot had been the victim of 'mickey or minnie'. Sealed the chewed area. 'Bang' issue resolved!!