HVAC Unit: Dis-assembly and Maintenance
EDIT: If any of these images ever fail to load properly, shoot me a PM. It appears Facebook sometimes alters the links to images and I have to update them before they work.
The goal of this write-up is to provide guidance to users wishing to perform maintenance on the HVAC control unit on their second-generation Subaru Legacy. This guide will provide direction on how to completely disassemble the unit into its component parts. This allows the user to perform the following tasks:
- Replacement on burnt-out illumination bulbs.
- Cleaning of blend door slider for smooth operation.
- Cleaning of other buttons that might have become sticky for... any reason.
- Changing of illumination colors to something other than green.
It is worth stating at this point that complete dis-assembly of the unit, while appearing complicated, is actually incredibly simple. I would say with confidence, that you don't really need to have any prior experience in ANYTHING to be able to do this without any issue. In other words, and this is not an exaggeration, I would feel comfortable letting a 5-year old follow this guide without fear of anything being broken. So if your only reservations to fixing your HVAC unit thus far have been out of fear, stop being a baby and let's get started!
CLARIFICATION ON BULB REPLACEMENT
Most of you will be looking at this guide because one or more of the bulbs in the HVAC unit have burnt out (a known issue with the bulbs in this generation.) Some confusion results if you do research and pull up more than one how-to on this subject. Some state that you can use standard bulbs found at RadioShack, while other state you should use bulbs from Subaru, which are more expensive. I'd like to clarify some things:
The RadioShack bulbs people suggest are the same bulbs that you would use to replace the bulbs in any of the other switches in your vehicle. They are very small, and are direct, and perfect replacements for all of those. HOWEVER, they are NOT direct replacements for the HVAC bulbs (with the exception of the one used in the A/C indicator light.)
The bulbs in the HVAC unit have two major differences. They are much larger, and whereas the green for any other portion of your vehicle is achieved by coating the inside of the illuminated surface with translucent green paint, the green in the HVAC unit is achieved by using bulbs onto which have been placed, for lack of a better term, green rubber condoms. This means there are two major issues with attempting to use RadioShack bulbs as a replacement. First, their smaller size means they do not sit properly, and do not project their light into the plastic diffusers properly, and second, their small size means you cannot transfer your green condoms to them (assuming you get them off the old bulbs without tearing them - they are incredibly brittle.)
You can solve both of these problems with some effort, but believe me it is worth it to just get the replacement bulbs from Subaru. Mine cost $13 total. There are three of these that you need. Two are the same, and one is different. You can see them in the following image, with their part numbers. The computer system at the parts counter will pull up various part numbers for different years in our generation, but the "latest" version of the bulbs are these part numbers, and if you get them, they WILL work. Order these, and once you've received them, proceed on!
REMOVAL OF THE UNIT FROM THE DASH
I neglected to take photos of this portion of the job, but I think words will suffice here:
Open the cup-holder in your dash located below your HVAC controls. You should see two screws, one on each side. Remove them.
With those screws removed, you should be able to slide the cup-holder assembly out from the dash. You should now see that the lower trim piece (radio bezel) and the upper trim piece housing the HVAC controls are held in by those two same screws. You should be able to wiggle the upper trim loose without removing the lower one, even though the lower trim sits on top of the upper one. The upper trim seats over the two plastic ducts for the air vents, so it needs to come out towards you a good half inch at least before you can slide it up. There is a harness connecting the hazard switch which you will need to disconnect in order to get it completely out of the way, or you can just set it on the dash.
You should now have access to your HVAC unit in all its naked glory. It is secured into the dash with four screws... one at each corner. As you remove these, be sure to hold on to them. If you let them drop down into the console, you will be lucky to get them back without doing a lot more dis-assembly!
Disconnect the harnesses going to the rear of the unit. There is one harness for the fan speed knob, one harness for the various vent modes, and one small harness lower down for the A/C switch.
The only thing left is to disconnect the cable going to the blend door. This involves removing two c-shaped clip rings. One of them retains the end of the steel wire (to a pin on the slider arm.) The other holds the cable steady a bit further back. For the first one, it's generally easiest to use pliers to squeeze it off, whereas for the second, you should be able to grab it and just yank it off. Don't lose them either!
If you've made it this far, you have done all of the difficult work. The rest is easy, so grab a beer, and let's get cracking!
This is what you should be looking at. If this isn't what you are looking at, something went horribly wrong, and you might as well give up working on cars altogether.
The first thing we can do is remove the A/C control switch. Look at the back, and you will see a plastic tab. If you bend this tab down, you can press the A/C switch forward and out the front of the unit.
Once it has been removed, you can replace this bulb if it is burnt out. This is the one bulb that you CAN replace with the same RadioShack bulbs that you would use for all the other switches. Just unscrew the bulb (bottom of the switch) about 1/8 of a turn and you should be able to remove it.
Next we will remove the protective cover for the circuit board. There are two tabs that just need to be bent back slightly and the cover will slide up and off!
Now we can release this smaller, brown board from its bracket and get it out of the way. Where the tip of the pen is in this photo is the clip you want to bend out (to the right in the photo) in order to release the board. Simply pull up on the board as you bend the clip back.
The ribbon cable will get tight as you slide it up, but don't worry. It is very sturdy and you won't break it. Slide the board up and out of its bracket.
Flip the unit upside down, and you will find two screws. Remove them. Note the clips just ahead of the screws that you have to bend up slightly when you slide this part out, which we will do after we do one more thing.
You need to remove the slider from the front. You just pull it off. Feel free to pop it off with something. It might be difficult, but you won't break anything. It's just snapped on nice and tight.
Now you should be able to slide out the whole lower assembly that controls the blend door. Might take a little shuffling and wiggling back and forth but it will come out.
If your goal was merely to replace the three bulbs, then this is as far as you need to go. You can see the two black bulbs on the left side, and the one taller blue bulb on the right. Replace them (they twist out counter-clockwise like 1/8 of a turn) and you are good to go!
Next we will remove the airflow buttons from the front. Your first instinct might be to dig a knife or something waaayyy under the switch to pop it off, but if you look underneath, they are molded with little depressions, so you can just slide the knife straight up underneath into that slot and they can be popped off easily. Removing the fan speed control knob is more difficult. I don't really know of a good way to do it.
To remove the fan speed control unit, you need to pop up this tab, and two more just like it on the bottom. If you're diligent, you can get them to all stay popped up, and then you can pry it out. It should slide out easily, but if you're like me, you couldn't get the knob off the front, so you just pry it out the back until the knob pops off the front. (Nothing is in danger of breaking, you just need to apply enough force to pop the knob off.)
I forgot to take a photo, but there are two screws in the upper corners of the big green board that you need to remove. Then you lift up on the two tabs that the board is snapped into (at the top), and you can pull it out. If it seems like things are falling apart uncontrollably, don't panic. Everything can be re-installed individually, just all the pieces come out at once.
You have a few parts in the above photo. The two boards, with the tiny LED indicators soldered to them. The clear plastic light diffuser that distributes light to the vent mode buttons. Then you have those black shells. They are what the buttons snap on to. They can be placed one at a time back into the HVAC chassis before you reinstall the board. You can kind of figure out which way they go by looking at them, and they can't go in upside down anyway.
The last piece you will see in there is another clear light diffuser. This can be easily removed by releasing it from its two clips (one on each end.)
Mine is blue because I had changed the color to blue as an experiment, but I am going back to green for uniformity so that was all removed.
These are all the parts you should have now. In this photo, I had also removed the fan speed stickers to remove the blue coloring I had applied to the back. I have also disassembled the slider arm a bit to get at the tiny piece of clear plastic there that lights up the slider.
One thing I HIGHLY recommend doing is dismantling the grey slider arm (upper right of the photo.) It is so straightforward I don't think I need to explain it, but if you remove all that stuff, and clean ALL the disgusting grease off of it, replace it with two or three drops of oil, and reassemble it, you will see that your slider moves a lot more freely and clicks more authoritatively into the detentes that are now not all full of goop!
Obviously, re-assembly is everything you've just read in reverse. Cheers on your reconditioned HVAC unit!