HVAC Problem

[JoshBarber]

just curious if theres a common cause of a strange venting (fart) sound that comes from under the passenger dash. can't find anything consistent about it, other than that its commonly heard right after start up...but sometimes even while its been running for a while. anyone?

[nickledimed]

What have you been feeding those Squirrels?....lol....is it loud?....does your truck have a computer climate control?....if so, does it go from hot to cold ok?
I just replaced the mixture control moter for the climate control in my truck....before it was stuck on hot....and it would make that sound you are talking about...what happened was that the Gear inside that is made of tephlon broke and what you heard was the gears rubbing against eachother.
Hope this helps....if this isnt what it is Im at a loss to help you....
P>S> the noise mine made was very faint but still bothersome.....I bought a new one for about 200 bucks but it is an upgrade.....The gear isnt made from tephlon anymore.

[dmbrisket 51]

air gurgleing in the heater core possibly? 96 or newer, plastic intake take a shit just now or just recently to where the coolent is or was down?

[garylee]

I have a '97 and my father has an '96, we both had the same problem. I even brought mine to a dealership, OF COARSE, they didn't hear it. So, months later I figured it out. It seams even though the coolant tank showed it always being full, I just kept adding to it, drive for a day or so, add some more untill it stopped. It worked for my Dad too. It gave me the impression that the FULL line on the tank is way off (low). It's been a couple years, no gurgling sound. There is a God! (wiping tears)

[Rmbodie]

Another posiblity . A sound I hear shortly after startup . As the air flow controls get vacuum , the panels inside the are moving -dragging against something . Rob

[mike2004tct]

RFG acting up (Random Fart Generator).

Or possibly a vacuum leak in the blend doors. The control sits to the right side of the temp wheel, and there's an Octopus of vacuum lines exiting the unit.

[nickledimed]

do you smell something shortly after you hear it?....lol
rotten eggs maybe.....lol

[JoshBarber]

Originally Posted by mike2004tct

RFG acting up (Random Fart Generator).

Or possibly a vacuum leak in the blend doors. The control sits to the right side of the temp wheel, and there's an Octopus of vacuum lines exiting the unit.

How do you access the Octopus of Vac. lines you're talking about?

[JoshBarber]

Originally Posted by JoshBarber

just curious if theres a common cause of a strange venting (fart) sound that comes from under the passenger dash. can't find anything consistent about it, other than that its commonly heard right after start up...but sometimes even while its been running for a while. anyone?

The problem has become more constant now...and very annoying.

[muddog321]

If this is 2nd gen Blazer look behind the glove box for the vac controls.
Have you flushed the heater core cause thats the #1 reason for water noises or gurgling behind the dash - but good farting noise does sound vac related.

[JoshBarber]

Originally Posted by muddog321

If this is 2nd gen Blazer look behind the glove box for the vac controls.
Have you flushed the heater core cause thats the #1 reason for water noises or gurgling behind the dash - but good farting noise does sound vac related.

Muddog321 - I've pull the glove box to gain access to the area but still can't find the source..although it IS loud. It seems like its coming from the compartment to the left side closest to the center console.

I've also determined its SOMETHING TO DO WITH THE HVAC system...when you pull the fuse for HVAC, it stops making the noise. Also something to note: when it makes the noise it the heat temp changes from COLD back to HOT. It makes the noise whether the fan is shut off, or on.

HELP!!

[JoshBarber]

Blazee -

I read your great post on trouble shooting heater issues.
I have had a random fart noise coming from my passenger side under the dash for some time, but it was random.

Last night I pulled the battery cable to reset computers (could be a huge coincidence) and this morning, the fart noise has become almost CONSTANT.

I've also come to notice the following things:

1. Heat changes to Cold, then back again whenever the noise arises.
2. The noise stops completely when you remove the HVAC fuse on the drivers side.
3. It seems as though some ammount of heat has always leaked out regardless of whether or not the fan was set to on or off (even though you dont HEAR the fan on).
4. I've removed the passenger side glove box, and thats as close as I can get to it.

I wondered if this would be a VACUUM leak of some sort, or an electrical issue? What are the chances of it being the HVAC RELAY, or HVAC RESISTOR?

HELLLLP PLEASE!?

[JoshBarber]

I've located what I believe to be the problem in this image.
Above the heater box on the passenger side, theres what appears to be a relay of some sort, with an electrical connector running into it. Here as you can see I removed the connector, and it killed the noise. With this connector out, the blower still blows, but you get NO HEAT.
Can someone tell me exactly what this part is and what it does? I'd think I would replace it to fix the problem, but Im afraid maybe its just what CONTROLS the thing thats making the noise. Like maybe it controls a door, and the door gets stuck? Or it could be just making the noise itself..

ANYONE?

[blazee]

Being that the temperature flucuates and the noise goes away when you pull the fuse, the first thing that comes to mind is the motor on the blend door. It's what mixes the air temp, if it's binding it may cause the noise.
There are three fuses for the HVAC. Which one are you pulling? There's a 30amp in the fuse box under the hood. There's a 20amp (fuse number 3) in the fuse box on the side of the dash, and 10amp (fuse number 21) in the fuse box on the side of the dash.

The 30amp is for the blower motor and shouldn't an effect on anything inside that could cause a noise. The 20amp is for the controls. The 10 amp is for the blend motor.

[blazee]

Sorry I missed the picture. You posted it while I was replying. That is a picture of the blend door motor.