Mission Impossible - Air Mix Servo

[riverwolf]

Specifically, the passenger side air mix servo in a dual zone system.

As the 4th gen ages, we're starting to see more and more reports of noisy servos. Happens when the contact fingers inside the servo get worn and the HVAC computer can no longer determine the position of the servo so it's constantly hunting back and forth and thus the noise.

With confidence inspired by the ToyotaNation thread of numerous folks successfully replacing the air mix servo on other Toyota/Lexus vehicles, I ordered a replacement from Partznet before diving in. Only to discover that, at least on the 4Runner, there appears to be no way to get to the air mix servo's upper right side screw without removing the blower assembly housing. Which, according to the FSM, entails pretty much taking the entire dash out of the vehicle. I could blindly put a fingertip on the screw, but there was not a path or room for any type of tool. Mission aborted. I hope to cut a deal with the local stealer when they do my dash pad replacement since 95% of the work needed to get to the air mix servo is part of the dash pad process.

In the meantime, if anyone successfully works out a DIY method to replace the air mix servo (not to be confused with the vent mode servo above it), I'd love to hear it.

-Brent

 

[CookieRoe]

This is scary b/c I'm noticing "clicks" behind my dash. I also have the dual system.

Subscribed.

 

[JEL]

Hmm it wasn't too bad in my 3rd gen Limited to replace the mix servo, it was stuck shut (or open?) so only cold air was getting in, that sucked when in the mountains skiing and ambient temps were only 5*F!!!

In any case, there was a blind screw as you mentioned on the 3rd gen as well, it was also on the passenger side, and I rigged up a magnetic screw driver, and mechanic's mirror, and my brother as a helper and I painfully did extremely slowly and upside down. All-in-all, not terrible but quite tedious, if you can get the dealer to do it while the dash is out I certainly would.

I'm worried now about my 4th gen, as I've also noticed a little bit more noise coming from the depths of the dash and I've had a couple instances when it takes a bit longer to change from cold to hot...


Come on Toyota, what's wrong with the good old knob-style climate control? :/

 

[BlackWorksInc]

Did you try one of those IKEA furniture ratcheting screwdrivers? You know the cheap ones you put a short philips bit in?

I've found those to help a ton in those types of situations.

 

[ThirdDeviation]

I just today finished removing the blower assembly, swapping out the vent control servo and replacing the housing, all without removing the dash. I followed the process outlined by Alldata, which you can access for free via AutoZone's repair instructions for the blower assembly. Or, if you have time to wait, I took pictures so I could put together a how-to. It might take me a day or two before it's complete.

 

[riverwolf]

I just today finished removing the blower assembly, swapping out the vent control servo and replacing the housing, all without removing the dash. I followed the process outlined by Alldata, which you can access for free via AutoZone's repair instructions for the blower assembly. Or, if you have time to wait, I took pictures so I could put together a how-to. It might take me a day or two before it's complete.

Third, it'll be a while before I have time to take another whack at it so I'll patiently wait for your writeup.

Took a look at the Autozone instructions and it seems to match what I remember of the FSM. I may have made an incorrect assumption that the dash pad itself had to come out...the FSM has a lot of "see this page" and "see that page" for each piece that needed to be removed to get to the blower housing assembly and since my PDFs aren't linked, I didn't actually read each "see this..." page. Still looks like a lot of stuff has to come out. Maybe with your write-up, I'll schedule a weekend to do the servo and upgrade the head unit since it looks like that's the path you took to get the blower assembly out.

BTW, I think there are few folks around here who managed to replace the mode servo without needing to pull the blower assembly. I didn't try to reach all of the mode servo's mounting screws, but a visual inspection suggested it was possible when I pulled the glove compartment panels trying to reach the air mix servo.

Thanks!

-Brent

 

[riverwolf]

Come on Toyota, what's wrong with the good old knob-style climate control? :/

I think pretty much every manufacturer has replaced the old steel HVAC cable actuators with electric servos. In manual HVAC systems, they're mostly set and forget. However, in an auto system like the 4Runner's, the computer is constantly tweaking the air temperature mix to maintain your set temperature so that servo gets a lot more wear-n-tear than it would in a manual system.

-Brent

 

[2003-4x4runner]

I'm also getting the servo clicking sound. Not sure if it helps anyone, but I found this on-line showing were all three servo's are located.

 

[TowelThief]

I just today finished removing the blower assembly, swapping out the vent control servo and replacing the housing, all without removing the dash. I followed the process outlined by Alldata, which you can access for free via AutoZone's repair instructions for the blower assembly. Or, if you have time to wait, I took pictures so I could put together a how-to. It might take me a day or two before it's complete.

Sweet. Post it up. Mine starts to hum super loud. And I have to shut if off and turn it back on lol.

 

[jaycar4]

Mode Servo Replacment

Hello,

Wanted to find out if someone can provide information on taking out the "Mode Servo" from a 2004 4Runner? I can see servo after taking the glove box and one of the vents out. But getting to the 3 screw seems almost impossible. I have seen discussion on removing the blower motor to access the servo and people seem to have done it without removing the blower motor. Any suggestions on how to take that 3rd screw out be great!

Thanks.

 

[silverbullet07]

I just today finished removing the blower assembly, swapping out the vent control servo and replacing the housing, all without removing the dash. I followed the process outlined by Alldata, which you can access for free via AutoZone's repair instructions for the blower assembly. Or, if you have time to wait, I took pictures so I could put together a how-to. It might take me a day or two before it's complete.

Did you ever put together putting a DIY together to remove blower assembly?

 

[silverbullet07]

After reviewing the auto Zone Guide. https://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f802c5591

Looks like the best option is to remove the Blower Motor assemble.

 

[laufer]

Air mix servo replacement both sides (2004 Limited) with part numbers

After reviewing the auto Zone Guide. https://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f802c5591

Looks like the best option is to remove the Blower Motor assemble.

IMPORTANT CORRECTION 2018-10-29: Contrary to what I wrote below, the passenger side part actuates in the opposite direction of the driver side part, so they are NOT equivalent and one cannot modify the passenger side part to serve as a driver side one. If you have a Limited, you need the correct driver side part number 8710635170 (replaces 8710635130).

I recently had the noisy air mix servos replaced on both sides on my 2004 Limited. This took the shop about 2h. While they did not remove the blower motor assembly, they emphasized that the top screw on the passenger side was very hard to remove and put back.

For the record, I also wanted to point out the correct part numbers so others can avoid the mini-odyssey I went through. It turns out that the driver side air mix servo, part number 8710635170 (replaces 8710635130), is mislabeled in both the parts catalog and the repair manual, respectively:

• SERVO SUB-ASSEMBLY DAMPER (FOR BLOWER); DAMPER, NO. 1.
• Independence [sic] Temperature Control Damper Servo Sub-assembly

Only in the wiring diagram (a separate document), section G p36, Position of Parts in Instrument Panel, is it identified correctly as Air Mix Control Servo Motor LH (Limited only), but I noticed that too late.

Because of this confusion, I had ordered two times the passenger side part 8710635180 (replaces 8710635140). The good and entertaining news is that the Denso servo motor is exactly the same for both sides, and one can easily convert a 8710635180 into a 8710635170 by

• unscrewing and removing the metal mounting bracket
• cutting off the shorter end of the white plastic arm

You can verify this by looking at the pictures on eBay. The shop had no problem making this modification on the spot.

FWIW, I ordered these parts from PartSouq in UAE, genuine OEM for about half off, shipped via FedEx for about 15% of the subtotal.

In sum, if you have a Limited, you need one of each of these:

• https://parts.toyota.com/productSearch.aspx?searchTerm=8710635170 - driver air mix servo
• https://parts.toyota.com/productSearch.aspx?searchTerm=8710635180 - passenger air mix servo

 

[Hair2burn]

Mission impossible or let’s say improbable regarding the air mix servo

Hello 4th Gen owners out there. I just want to thank the 0P. It’s gave me a lot to go on regarding the symptoms surrounding my sudden no heat issue on my fourth Gen Sport V6. I went to the dealer this evening and priced out various parts at the counter. The lady was kind enough to print me out a schematic of the parts that were mentioned above. While it was just before closing time I met a young tech who saw what I was dealing with and he had some mercy on me. I asked if he could help me, and he kindly popped the hood and started trying to find the cause. His first thought was low coolant which I assured him I had just topped it off. He checked for himself anyway and He took the truck into his service bay to check for air pockets. I told him about the buzzing sound upon start up. He then took the glove box off and exposed the lower panel. He could hear the buzzing sound each time I turned on the ignition to the accessory. He then asked for a screwdriver and he begin poking on the plastic housing of the air mix servo. The buzzing sound stopped and the heat miraculously returned. I think something was lodged in the servo motor motor and poking on the outer housing did the trick. FYI he was cycling through the different modes while he was poking on the housing. Defrost, face vents, floor vents and repeat. The only thing I can think of is that he gave the system a good work out and whatever was lodged in there became dislodged.

Anyway I am grateful that I did not have to tear down the dash or make/ fabricate a tool to get a stubborn screw out to remove the servo.

I hope that this post helps somebody and perhaps you should give it a good couple of pokes while cycling through the different air modes.

Now I’m onto a 5th gen total brake swap w calipers. (Mine have seized once already)

And after that I’m trashing my xreas system!!
And installing FJ springs w Bilstein 5100’s!!

Cheers to you all!!

 

[cnd4747]

A little over a year ago, I had this issue (grinding noises, stuck on cool air, may sometimes blow hot briefly but not for long -- The modes worked fine), and got the driver's side left air mixer (87106-35170 Serve Sub-Assy, Damp) on my T4R replaced at a dealership. The repair worked for a bit under a year, but the issue returned. Videos of the grinding sound, since it helps to hear it.

• https://www.youtube.com/watch?v=VQpK-WvysXg
• Grinding noise on 2003 Toyota 4Runner LE on startup - YouTube

I don't think this is the case, but it's possible it's just a second mixer sub-assembly that's failed. I'm starting to think there's something underlying that could be causing an issue here. Is there any sort of electrical issue that would cause this to fail repeatedly?

I recently replaced the battery -- the old one was cracked and leaking acid! -- and the AutoZone tech said the battery I was using wasn't the recommended size but that it would work. Could this cause some sort of electrical fault which would mess up the servos? At this point idk.

 

[AuSeeker]

A little over a year ago, I had this issue (grinding noises, stuck on cool air, may sometimes blow hot briefly but not for long -- The modes worked fine), and got the driver's side left air mixer (87106-35170 Serve Sub-Assy, Damp) on my T4R replaced at a dealership. The repair worked for a bit under a year, but the issue returned. Videos of the grinding sound, since it helps to hear it.

• 2003 Toyota 4Runner grinding(?) noise from behind dash - YouTube
• Grinding noise on 2003 Toyota 4Runner LE on startup - YouTube

I don't think this is the case, but it's possible it's just a second mixer sub-assembly that's failed. I'm starting to think there's something underlying that could be causing an issue here. Is there any sort of electrical issue that would cause this to fail repeatedly?

I recently replaced the battery -- the old one was cracked and leaking acid! -- and the AutoZone tech said the battery I was using wasn't the recommended size but that it would work. Could this cause some sort of electrical fault which would mess up the servos? At this point idk.

A 12 volt battery is a 12 volt battery, so no the battery wouldn't causes the servo to fail, these servos are known for failing unfortunately but they usually last for awhile, yours being a 2003 I would say 20 years isn't bad for a servo to last and is a good "while", but the limited has 2 "blend/air mix" servos one for the driver side and one for the passenger's side I would say the other one has failed.

It easy enough to tell, by if one side is not the same temperature as the other when both are set the same and you raise and or lower the settings.

 

[cnd4747]

That all makes sense about the battery -- got worried by the sales guy and wasn't thinking straight. Both times have been the entire driver's side area, though. I guess they're designed to work in tandem and if one fails, the other can't keep up on its own.

 

[Rocket3004]

What kind of clicking sounds are you getting? Is there a sound clip available? Also any other symptoms?

A few mos ago I got a noise which went away - but to me it sounded more like a leaf or something caught in the blower since the cadence changes with fan speed.

 

[cnd4747]

What kind of clicking sounds are you getting? Is there a sound clip available? Also any other symptoms?

Yeah, there's two YouTube links in the top post on this page (the underlined bullet points), kinda hard to hear but that was from my car before the last repair a year ago.

The symptoms are:

• air is largely only 1 temp (max cool) -- regardless of set temp
• clicking/grinding noise from dashboard/steering wheel area