HVAC Problem

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?

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.

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?

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)

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

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.

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

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?

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.

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.

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!!

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!?

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?

http://i16.photobucket.com/albums/b40/JoshB_/relay.jpg

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.

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

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


"Blend Door Motor" That sounds about right.
Do you think its the motor? Or the door itself getting stuck?
You ever replaced it?? It looks near impossible!
Do you have a part number for it?

What kind of fart noise is it making? There are a lot of different sounding farts. Is it a creaking sound or a ripping sound? A creaking sound would seem more like something sticking. A ripping sound could be the gears inside the motor slipping.

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


Just called the dealer, they're calling it a "Actuator Temp Valve" and its a $187/ea part.

What kind of fart noise is it making? There are a lot of different sounding farts. Is it a creaking sound or a ripping sound? A creaking sound would seem more like something sticking. A ripping sound could be the gears inside the motor slipping.

It sounds like a groan/creak...like RRRRRRRRRRRRRRRRRRRrrrrrrrrrrrrrrrrrrrr
starts strong and peters out to nothing. Kind of like a bullfrog low croak.

What kind of fart noise is it making? There are a lot of different sounding farts. Is it a creaking sound or a ripping sound? A creaking sound would seem more like something sticking. A ripping sound could be the gears inside the motor slipping.

I dont think the creak noise is normal.........but -
what would cause it to be adjusting constantly regardless of the fact that the heat controls are shut off?

is it possible its a sensor, or relay elsewhere? if so where? or would the motor turn itself on and off by itself if its EFFED up?

does anyone have access to the wiring diagram for this part?
I would like to check the connector with a meter to see if its sending power to the unit at ALL TIMES and if it in fact should or not. Im looking for what the output numbers should be on this connector shown, with the key on. Its a horrible task to try to remove this and I'd rather determine its this part ($200) and make sure its not just getting power when it shouldnt be.

thanks
J

Turn the key to run, or start the engine. Pull the connector off and check the power there. You should have three wires. The black is ground. The brown should be hot. The light blue should scale up based on the position of the temp control switch. With the switch at full hot there should be 0 volts. The voltage should climb as you turn the knob to cold. When you get to full cold it should read the same voltage as the battery.

Here's the schematic:
http://www.myfilehut.com/userfiles/13931/Heat/Figure%2020%20ZOOM.JPG

Here's the schematic:
http://www.myfilehut.com/userfiles/13931/Heat/Figure%2020%20ZOOM.JPG


Oh man, Blazee....
thanks SOOOO much! this will help big time.
I'll print this and check these tomorrow and should have a good idea if theres a problem BEFORE the actuator, or if its the actuator itself. $200 for an unreturnable part that Im not sure is the problem is a little more than I can spare!

If its the actuator....I'm gonna beg you for a removal procedure. Ive tried a few times to get my hand in there to the 3 mounting screws and it seems impossible. You must have to remove the upper section of dash on the Passenger side.

Most people pull the dash. A while back, a guy posted that he got if off with out pulling the dash, but it was a PITA. I would try it without touching the dash, even if its a real pain in the ass, it should still be easier than pulling the dash.

If you decide to remove the dash. You'll need to remove all the under dash panels and the knee bolster. There are two bolts at the bottom of the dash. (one on each side) they are 10mm. Below the steering column there are two "L" brackets, each bracket has 4 - 10mm bolts, you'll only need to remove the ones that are hard to get to. On top of the dash, there are 6 - 7mm screws. One under each speaker grill, and four under the defrost vent. The whole dash will roll forward after you remove all the screws, so that you can access behind it.

After you get it off, you can manually move the door to make sure that there aren't any obstructions, and that it is working properly.

Most people pull the dash. A while back, a guy posted that he got if off with out pulling the dash, but it was a PITA. I would try it without touching the dash, even if its a real pain in the ass, it should still be easier than pulling the dash.

If you decide to remove the dash. There are two bolts at the bottom. (one on each side) they are 10mm. Below the steering column there are two "L" brackets, each bracket has 4 - 10mm bolts, you'll only need to remove the ones that are hard to get to. On top of the dash, there are 6 - 7mm screws. One under each speaker grill, and four under the defrost vent.

After you get it off, you can manually move the door to see if there are any obstructions, and that it is working properly.

It sounds like a MAJOR bitch to get the dash off. Is it? Then of course the inevitable squeaking that will follow for the rest of me owning it over bumps etc. :)
Although, it would be nice to know for sure if theres obstruction or not on the door itself. What do you reccommend?
Its really wierd. Its like on a clockwork if you turn the key and watch the actuator move the shaft on the door. It turns and sqeaks all the way to one side. Pauses for about 2.5 seconds, and turns and squeaks all the way to the other side. And it repeats this constantly with the key on or running. If you have the temp control ON, it changes from cold to hot on each rotation. I cant figure out if the controls are f3c&ked and are sending it this repeated message, something like a relay BEFORE the actuator, or if the actuator itself has a brain of some sort in it, and because its screwy it just continues to move back and forth.

I edited my last post and added a little more info while you were replying.

Rolling the dash is a bitch the first time that you do it. After you know where everything is and how to access it, it's not as bad, but....... it's still a bitch. ;)

It does sound like you have a control problem. You should know for sure after you test the voltages.

If it is the actuator that's bad, you'll still be able to test the door manually after you get it off even if you removed it without touching the dash.

I edited my last post and added a little more info while you were replying.

Rolling the dash is a bitch the first time that you do it. After you know where everything is and how to access it, it's not as bad, but....... it's still a bitch. ;)

It does sound like you have a control problem. You should know for sure after you test the voltages.

If it is the actuator that's bad, you'll still be able to test the door manually after you get it off even if you removed it without touching the dash.


How so? Just by putting pliers on the door shaft manually?

Hey Blazee -

Looking at the schematic. Does the highlighted area suggest the Actuator in question? And if so...does the "valve SENSOR AND MOTOR" suggest that the actuator itself has some brains in it itself? Or am I jumping to conclusions?

http://www.geocities.com/rudemoodz2001/smallschematic.jpg

Blazee-

The schematic you gave me for the "Air Temp Valve Sensor" shows to only have three wires running to it. Brown, Light Blue, and Black.

Mine, has 5 wires in the connector.

BROWN, BLUE, YELLOW, LIGHT BLUE, LIGHT BLUE w/ Black


Are you sure I have the right schematic for a vehicle with AUTO temp.? Also, this shows 3 left dash fuses. I have the HVAC fuse which is 10amps filled. The HVAC1 fuse, which is 20amps, has never been in since I owned the vehicle, and a ILLUM Fuse which is 10amps. is filled.
I can't register ANY changes coming through the connector (which would lead one to believe its the pot on the thermostat knob...BUT I CAN'T BE SURE, BECAUSE I DONT KNOW IF I HAVE THE RIGHT WIRES HOOKED UP. CANT EVEN FIND A BLACK/GROUND WIRE.

Could you get back to me and let me know if you have the correct schematic?

thanx again
J

The schematic I posted was for a normal HVAC system. Unfortunately I don't have one for the auto AC system.

The schematic I posted was for a normal HVAC system. Unfortunately I don't have one for the auto AC system.

F8CK!!!!!!!!
anyway I can get that schematic? SHIT SHIT SHIT!
I actually tried EVERY wire though with the other connected to ground, and saw NO CHANGE throughout the temp wheel adjustments.

UGH!

I don't know much about the auto units, so without some schematics or a flow chart I don't think I'm gonna be much help. Maybe one of the guys with an alldata subscription can get the schematics for us.

I don't know much about the auto units, so without some schematics or a flow chart I don't think I'm gonna be much help. Maybe one of the guys with an alldata subscription can get the schematics for us.

do you know anyone in particular I could beg for this diagram?

I think that we have a few members that have alldata subscriptions.

MT-2500 seems to have access to a lot of schematics, too.

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?

http://i16.photobucket.com/albums/b40/JoshB_/relay.jpg

This is the mixture control moter I was talking about and it is very tight in there...I dismantled my dash to replace it.

"Blend Door Motor" That sounds about right.
Do you think its the motor? Or the door itself getting stuck?
You ever replaced it?? It looks near impossible!
Do you have a part number for it?

if its a 98 or newer I have th part numbers...if you still need them

just anouther quick note....when you dismantle the dash you will have to drop the steering clomn, its not as bad as it seems the dash just rolls back after you take out 3 screws on each side..I think they are 10mm or 12mm not sure which. it is very time consuming though, now when you get the mixture control moter off you can chack the blend dorr to see if it move freely...DO NOT USE PLIERS ON THIS. you should be able to move it reely just by turning it with you hand. If it is stuck you will have to disassemble the blend box, but this is very rare. now if you have read the second post in this thread you should have a very good idea whats going on here....best of luck and if you have any questions post here or pm me....

How do you access the Octopus of Vac. lines you're talking about?
remove the center consol, then remove the knee bolsters it is right under the a/c control switches.

i have this exact same problem with ac going hot cold hot cold. did anyone ever figure out what the exact problem was. please help.

Is there a way to move the door manually without removing the dash? I would like to try this before I spend the $200 or so on the part and about 6 hours of labor.

it is the ac temp actuator that is on top of the ac box behind glove box. it retail for almost 200 at dealer but i got one dealer to sell me one for 130 something plus tax. took me about 1 1/2 hours to put in. didnt remove nothing but glove box and a few trim panels. also removed vacum switch infront of temp cactuator to make more room for my hands. also cut a small piece of the rubber firewall insalation out to make room to turn rachet and remove temp actuator switch . just duct taped rubber back iin place when done. afterdone replaced battery cable that i had removed before starting and car was fixed.