A/C defrost intermittent +other ?issue?

[campb292]

Apologies in advance for my lack of precise knowledge.

Recently I replaced a blower motor in a 06 Vibe with about 155,000 miles. Replacement blower motor continues to work fine. This was two weeks ago.

Today I noticed the usual loud noise I hear when turning to defrost/defog (same noise as when turning on the A/C) was gone. I am not sure if this is the AC compressor or condenser? I fiddled back and forth between the regular vents and defrost and it just wouldn't make that loud noise. Pressing the AC button didn't make the louder noise. After an hour, I tried it again and it worked - made the same loud noise and could be triggered by pressing the AC button or moving to defrost.

This just a below "x" temperature thing I never noticed before? Is that loud noise the compressor?

Thanks in advance for any info... love this car and want to keep her running well!

[JohnO]

My guess is that it was unusually cold this morning. A/C units usually will have a temperature sensor that will prevent the compressor from running below a certain temperature generally somewhat below freezing. This is perfectly normal.

[campb292]

Thanks John.

I was listening to things and also notice the main cooling fan kicks on when I turn to defrost/defog or turn on the A/C. The loud noise I mentioned earlier sounds like it is actually the fan. It actually wasn't abnormally cold here, may 25F or so. I swear I have heard it turn on before at temps even colder... if the loudness I am trying to describe is actually just that cooling fan (the big one right next to the radiator) could this be tied to a failing thermostat or something?

[Rayven01]

The 09 Vibe manual specifically mentions the AC compressor only running above 32F/0C. No idea where it's measuring that temp but if it's inside the engine compartment it could be significantly warmer than that with a hot engine even when it's cold outside, but match the external temp with a cold engine. Could explain your varying results.

[JohnO]

Thanks John.

I was listening to things and also notice the main cooling fan kicks on when I turn to defrost/defog or turn on the A/C. The loud noise I mentioned earlier sounds like it is actually the fan. It actually wasn't abnormally cold here, may 25F or so. I swear I have heard it turn on before at temps even colder... if the loudness I am trying to describe is actually just that cooling fan (the big one right next to the radiator) could this be tied to a failing thermostat or something?

The cooling fans and A/C compressor will always run together, so whenever the A/C is selected or the defroster is on except with temperatures around freezing or lower in which case they may or may not come on. Is the noise louder than you remember it being in the past? You could give the fan a check. With the ignition off and engine cold (so the fan won't come on) give the blade a spin with your hand. It should turn without binding or rubbing on anything. Look for missing pieces or something stuck to it that shouldn't be there.

The earliest symptom of a failing thermostat is that the engine will start to take longer to warm up.

[campb292]

Thanks for the responses.

I see the 32F in my manual as well, so that explains the compressor thing. The loud noise has always been loud, I hear the same noise on any Vibe I am near in parking lots etc. It has always been loud with the defrost or A/C on and hasn't gotten louder recently. Just that one day it wouldn't turn on for an hour or so.

For a bit more info, let me explain why I am sensitive to defrost/AC and that noise. After about 90,000 miles I noticed when cold the car would vibrate/buck somewhat hard when idling at the first stop I make. For example, I turn it on, let it run for a minute or so, then drive out my driveway, get up to 55 or so then stop at a stop sign... at that sign, if I just have the vents on the car shakes and bucks like it is about to stall. If I turn on the defroster or AC, it never happens and is smooth (well, as smooth as the 06 Vibe can be). So, that day not noticing the noise I usually hear when kicking on the defroster meant hard idles until it is warm.

I guess I am just trying to catch something before it fails and is a bigger hassle. This car has been problem free really - the first mildly interesting part I have replaced is the blower motor. Nothing else has failed, just routine maint like brakes, oil, tires, battery, couple coolant flushes and a tranny flush. Oh, I did put new front struts on it.

[JohnO]

The problem may be a sticky idle air control valve. This is a valve that controls the amount of air entering the engine when the throttle valve is closed, thus it set the idle speed. It could by the valve is sticky at certain positions so when your A/C is off, the spot it wants to be in is sticky. When your A/C is on and the engine load is a little different the spot it needs to be in is not sticky. I plan to clean mine this spring. Here is a thread with info about servicing it that includes some great pictures:

viewtopic.php?f=17&t=36489&p=476353&hilit=iac#p476353" onclick="window.open(this.href);return false;

I don't think it is necessary to replace the round o-ring that people talk about in the thread as it doesn't look like it is a seal against a vacuum leak.

[campb292]

Thanks for all of the info. I haven't experienced this behavior again so I will chalk it up to temps and move on.

I do have one other issue I want to run by you, not related to the thread title but here goes:

When I push down on the front passenger-side of the car I hear what sounds like a slurping noise... kind of watery sounding. When I push down on the driver side (or rear), just sounds like it normally does but I can still hear the "watery suck noise" coming from the passenger side. It doesn't make any unusual clunks or knocks when driving, just never noticed that noise before. No bouncing at all from either side. Front struts have about 35k on them.

here is the noise, rough but you can kinda hear it. You need to separate the target noise from the sloshing of other liquids, but fwiw: http://webpages.charter.net/campb292/vibenoise.wmv" onclick="window.open(this.href);return false;

[JohnO]

I can hear the sound that you are referring to. I think the gas pressurized strut has lost its pressurization. That allows bubbles to form in the hydraulic oil as it is being forced through the orifices in the strut.

[Rayven01]

That's an.. interesting noise to hear from a car. What are you feeding it?

My completely uneducated guess would be strut as well.

[campb292]

On a rough look I can't see fluid leaking from it, but ya, seems like a strut problem. Guess I will be needing a new strut.