Manfred

Hey All, I have a high pitch sound coming from my dash area which is related to my HVAC system. The sound will briefly go ahead as I switch actuators with the vent slider but returns immediately. The sound is intermittently constant--meaning when it happens I can't get it to stop but it only happens about 1/3rd of the time I'm driving--appears to be becoming more frequent.

I remember reading a/some thread(s) about a certain actuator flap causing a reed-type sound--I guess my sound qualifies for that--sorta sounds like a 1st grader learning to play the clarinet. The thread commented that it was an easy and cheap fix--I just can't find the thread anymore. I do have Dwayne's HVAC thread bookmarked but I wanted to make sure I identified the actuator that's implicated in the reed-type sound before I pull everything apart. That way I can be particularly careful in inspecting that actuator if for some reason it appears to pass the test but I really suspect that it's my problem. If anyone knows the thread I'm looking for, I'd appreciated it.

Thanks, Dan.

Airflite40

probably a vacuum leak

Tampa 928s

Could be your internal temperature sensor, it has a little fan that when gunked up will make a high pitch whine!

DR

The Blue/Black HVAC Check Valve coming off of the brake Booster Vacuum supply is bad.

blown 87

My first thought.

Alan

What flap modes does it do it in - all or just one/some?... if all - then what Dave said... if only in some modes - which ones...

Alan

Manfred

Blown87--I wish the sound was that good.

Hey Alan, It happens in all modes; it will briefly stop if I put the slider halfway btw two modes but even then it will resume after a second or two.

I'll inspect the check valve today.
Dan

WallyP

The sound is usually generated by air flowing thru the blue/black check valve, and the sound can usually be stopped by replacing the check valve - BUT...

The sound is a symptom. The cause is one or more vacuum leaks in the HVAC system. If there are no leaks, there is virtually no air flow thru the check valve, and thus no noise.

tailpipe

Small animals camped out inside the heater vents? actually I agree with the vac leak you might be able to grease the outside and get a little more time out of it but its sounds like new seals are in order

Manfred

Just a quick update to everyone that's helped: did an HVAC R&R ala Dwayne's thread and found:
1. Leaking center console actuator
2. Partially failed blue/black check valve (inhibited flow in direction where there should be full flow)
3. Leaking vacuum solenoid to footwell actuator
4. Leaking hot water valve

I completed the center console diaphragm replacement but car is in pieces while I await arrival of the remaining parts...

My A/C actually was working pretty well before the noise started so I can't wait so see how cold it blows once I've taken care of the hot water valve!

As an aside, does anyone know whether these vacuum leaks could have been affecting my engine performance? At low rpms (by low I mean 3000) I feel like I do get a little stutter when accelerating--seems to improve as I pass 4k and move on up.

WallyP

The total amount of air that could be passed by the tiny hose at the brake booster wouldn't affect the engine at 3000RPM.

Manfred

Thanks Wally--thought that was probably the case but I really have no working knowledge how the vacuum plays into engine performance in the first place so I thought I'd ask.

I'm pretty certain I need a new O2 sensor and I know I need a need TPS so I probably won't worry about chasing down my sluggishness until I take care of those problems and see how it runs.