Nic Johnson

Hey,

I have a 2004 4Runner. I just paid it off, and not a week later this noise pops up. I had been hearing a chirping noise as if a belt was loose, and then that stopped and this buzzing/vibration noise started.

It only happens right after you crank the car, and it varies on how long or steady it is. Usually after about a minute, it's done. I have included an audio clip I recorded...it's much louder than came through on the recording.

It is coming from the center console area - underneath the stereo/a.c area.

I uploaded the audio clip here...you can here it at :10, and :19-:25

Any ideas? I don't know much about cars, and feel like a mechanic would take advantage of that...

toyota_tx

Finally I found some one with same problem! Yes I have the same noise, it is driving me crazy. Sounds like a relay buzzing, Have most of the dash out and of course it won't do it now. I do have an issue with my blower, so I decided to tackle that noise also. Blower was clicking for a week and then died. Pulled it out, cleaned all the carbon from it, bench tested it and it spun right up. Clicking noise is gone but will no longer work "in vehicle", prior to my cleaning it, not because of. Read diagnostic chart, it said to scope the AC amplifier, this is in dash below the climate control panel, must remove all trim around radio, climate control etc. Opened AC amp up, no relays inside, so this is probably not the culprit. Scope showed proper PWM output to the Blower Motor Controller so that is probably junk. I pulled the BMC, this is solid state, so no relay noise from this. There are two relay packs under the passenger side glovebox for the 4WD and TPS, i put my hand on them last time I heard the noise and I don't think it was them either. I see no other obvious sources of noise in the area behind the climate control or glove box area. Last culprit may be the VSC box located beneath the shifter, just aft of the cup holders. I'll drive around a few days with all that exposed to see if I can hear/locate this annoying little bugga. Hard to beleive only 2 of has have this problem.

BTW: 2004 4Runner Sport V8 4WD, 180K on it.

toyota_tx

Ok, so I drove several hours on Sunday looking for salvage yards in FTW. Another 2 hours Monday, flippng all the HVAC controls and not a peep. The BMC has on the bench in the garage all this time. Here is my theory: I popped the cover off it and saw a small SMT board and a large transistor. There is an obvious black burn mark on the buss bar opposite the transistor. The buss bar is wide and thin, basically L shaped and mechanically suported on the two ends. I suspect that the arcing is vibrating this buss creating the buzzing sound as the unsupported corner of the L shape is vibrating like a harmonica reed. Further, since the unit is heatsinked into the duct work for cooling, the sound is traveling right up the duct work and out the vents on either side of the radio, making one think it is behind the dash. Next step will be to try and get a new transistor, they run about 20 bucks, and see if this solves the blower and buzzing problem at the same time.

Electronic Details: marking on device is K2023, which I suspect to be short for 2SK2023-01, an N-Channel Silicon Power MOSFET, NTE replacement number is NTE2970.

Local Frye's did not stock so I'll have to order one in.

http://dilp.netcomponents.com/cgi-bi...umber1=NTE2970

toyota_tx

Day 3 driving aroud with dash and console opened up. It is not the Blower Motor Control, although mine has gone bad. no sound that morning but it did that night on way home from work, tried a quick feel and missed it, seems to be the rh side of the Air Conditioning Radiator Assy (Everything behide center of dash) did note that just as you found, it was right at start up, but not every time. Vehicle sits for a while, off, before it occurs again. So this time I was ready for it, and was kneeling on the passenger rb, reached over and started the truck. Suspecting it is one of the two ac damper controls, I unplugged each while it was buzzing. I can now say without a doubt it is the upper control on the right side of the ac unit. Toyota 2003 manuel page 55-11 calls it:
Mode Damper Servo Sub-assy
whilke the lower one is:
Damper Servo Sub-assy

Went junking this weekend looking for the blower control and struck out. I will pull this damper control apart in a few weeks and update y'all.

fable

Thanks for doing the research and updating us toyota_tx. I felt like I heard a similar buzzing noise behind my dash, but haven't heard it since. I am sure this thread will prove valuable for people making searches in the future.

toyota_tx

Glad I could contribute, this site has helped me in many other ways with both my '04 and previously the '94.

Yes the buzzing servo for the AC is the culprit, my BMC arrived today, 42.00 on Ebay. Will post a pic soon, Denso number matched and it came from an '06 Prius. Blower motor back in service on all speeds. The servo is still disconnected, and as such only the four face vents will exhaust any a/c or heat, regardless of vent selection. In spare time I will pull that out and see if it can be serviced on the bech with a relay change out or such. Stay tuned......

toyota_tx

Noise has gone away after removing the upper servo, dismanting it, putting 3 in 1 oil in the litlle electric motor. I suspect the nosie was not from the motor itself but being caused by the jamming of the cam plate while it is trying to move the 3 damper door levers. I was finally able to consistantly replicate the noise by switching the HVAC controls around with the blower on. (This was after replacing the BMC as noted previously, and putting a new blower motor in.) New blower on ebay around 43.00 form Direct Automotive Products, form and fit was excellant. R&R of the servo is possible w/o removing the entire center hvac assembly is possible but tedious. It is held in with 3 screws holding a silver metal bracket. I reccomend a flexible shaft screwdriver with changable phillips tips. I did not have one and used various drivers in length and width. As such I could only reach 2 of 3. A long thin driver was used on the upper back screw while reaching through the flip up damper door above the cabin air filter. There were 3 tiny scews going thrugh the steel bracket into the black plastic damper body. remove these and then the servo will be floating loose between the metal bracket and the body of the damper door housing. I then bent the bracket backward as far as possible. You can now slide the servo out.

The servo is snapped together and easily comes apart. Try not to break the tabs. Work it open a little at a time in rotation. There is a rotating cam plate. Make note on it's position and try to make note of where the damper doors pins are. This will be the biggest head ache in reassembly. The cam is greased, I redistributed the grease into the tracks, this alone may have fixed it, or maybe the realinging of the cam to pin locations fixed it. Reassembly required putting only half the servo back in, alinging the cam plate to the 3 damper pins and checking it's rotation back and forth several times to ensure smooth operation. Could not get everything to line up if I tried to install as a complete damper assembly. Could not line up the back pin as it was not visable. So put the cam half in first, get it smooth and then slide the motor halh into position, snap it together, bend the metal frame back into position, put at least 1 of the larger screws back so the servo does not slip off the cams, then the 3-4 small screws that go through the servo. Turn vehicle on and test the operation. If any binding of the cam/pin occurs, you'll know it as that buzzing noise will present itself. If the noise is gone, button it all back up and pat yourself on the back.

Dnb1111@gmail.com

I'm hearing a buzzing for about 10-15 seconds after I turn the key on. Not long after it started, my a/c thermostat knob quit responding. I can push the button to turn on and off the a/c but no matter how I turn the hot/cold knob, it blows cold, vent or a/c, no heat. I took the a/c instrument cluster out and when it's out, I turn the key and don't hear the buzzing. Thinking about replacing the cluster and see if it fixes it. Unless someone one here thinks it may be the heater servo that operates the air blend door?

texaricanrunner

I started hearing a noise, like a small air fan, behind the A/C controls. What is strange is that it keeps running even when the vehicle is off. This thing is draining my battery. What is it?

Jim Wooten

YESSS! Same thing in my 2008 Sequoia! Occasionally it sounds just like it gets up against something and sounds like a phone vibrating on something hard. When it's not against whatever, my grandson described it as a purring cat. He was right. Inside of console around base of shifter. I'm worried about this kitty thing overheating and startinget an electrical fire. There HAS to be a final answer!

texaricanrunner

So I found that the noise was a faulty (aftermarket) radio. Replaced the radio, end of chapter one of story (see my other post).