Why does my car not blow warm air? No Heat. AC works.

It's an 02 996 cab. The heat doesn't blow warm air. Ive already changed my digital cluster but that must not have been the problem. What else can I check? Wondering if perhaps I have a manifold air pressure leak and maybe it won't actuate the valves needed to flow heat? Or are they electric? Perhaps it is the heater core? Looking for things to check. Got any good ideas?

First thing to check is the coolant level.

Foam on the diverter flaps is gone. http://www4.rcf.bnl.gov/~nieuwhzs/98...p%20Repair.pdf

Quotes source post: 15644036

Read where one guy went through where his stereo is placed to do this repair. But he had no pictures and didn't say much. Anyone know how he did this repair without removing the dash?

Topped off the collant and I think it may have helped a tiny bit. Decided to pull codes: Getting a P0491 and P0492 (Current). Could these codes have something to do with my heater problem? I can feel the air flow from the Top, Middle and low sections when selected as such on the heaters control unit. But is there possibly a flap that can't engage because it runs on vacuum pressure?

get that coolant topped up and bled right ASAP

Quotes source post: 15645515

The coolant is definitely topped off. Had to add about 1/2 gallon to get it topped off. Are you saying that I have to do something else with the coolant? IE Possible air bubble? Any thought to these two codes having anything to do with the lack of heat?

Just went out and zip tied a few vacuum lines and now the car runs and drives a lot better. The codes are gone. But I still have no heat. Guess I will have to repair that flap door thing. Anyone know of an easier way to do this operation?

codes are air leaks for SAI and sounds like you fixed them- unrelated to the heat issue. IMHO, you have a large air mass in the cooling system and need to get it out ASAP before it does damage... for a basic cure, make sure the bleeder valve/clip is up/ filler cap tight and keep rechecking the level

I've had this problem with my car since I purchased it... I just figured the diverter thingy wasn't working correctly when I switched it to heat. My coolant levels are fine and my car temp has never ran hot. Would the air in the system still allow the car to keep from over heating? If so then what damage could it be doing? non Porsche guru inquiring

Quotes source post: 15646357

sounds like an issue with the HVAC system in your case air in the system can cause boiling or hot spots...in the engine for example can cause cracked heads, h.g. failure, detonation etc

Quotes source post: 15646366

thank you

Quotes source post: 15645792

I think the easiest hack is to go in from the frunk side, under the battery. Look around here on Rennlist, Renntech and 6 Speed Online for prior posts - it is pretty well written up. Here is one: https://www.renntech.org/forums/tuto...the-procedure/

Quotes source post: 15646401

Have you done this repair? The pictures on that guys tutorial are terrible. Can't see what he is talking about. I'd like to get large pictures so I can see where to go in etc. I don't want to just take a sawzall to my Porsche and go after a flap in the HVAC unit.

Quotes source post: 15643611

And why did you change the digital cluster???

It is very common on the "volkswagens" from the nineties. The foams on the diverter just fly away and on heat air can be directed to the cabin anymore.

Quotes source post: 15646697

You need to get to it - you can remove the dash (been there, done that, pain in the ****), or you can take the easy way and go in under the battery. Either way, it isn't a quick fix. Completely doable by a competent DIY, but not a no brainer. And there is no sawzall required (IIRC), just a dremel with a cutoff wheel.

Quotes source post: 15646749

I wondered the same thing! OP, this fix is not easy. Read about this one years ago because of the symptoms of foam in the air vents. Common symptom of the problem. I'm like you, I don't want to cut into my blower unit and so what I do during the winters, is turn off the air vents on the upper dash, redirect the air at the feet, turn the control unit on HI and enjoy lots of heat at the feet. Works for me.

Quotes source posts: 15646749, 15646886, 15646909

The digital part was not working. Bought one on ebay, simple replacement. OK. Sounds like I am going in, under the battery. From his pictures I couldn't tell it was under teh battery. I don't get lots of heat anywhere. Are we talking about the same problem? I'm assuming that this foam part of the vent directs HEAT. Let me re state- I don't have much heat at all. (lol- Sounds funny when I say it that way. )

There is a metal flap that pivots to divert climate control air in various directions. It has lots of holes in the surface (like swiss cheese), presumably for lightening the part. When new, the foam blocks off the holes. As the foam breaks down in old age, it comes apart opening up the holes. With the holes unobstructed, lots of air gets past the flap.

Quotes source post: 15646983

Have you thought about wearing thermal underwear? Electric blanket? Maybe, a 12 volt hair dryer?

Quotes source post: 15647068

So just go in under the battery and it should be fairly close?

Quotes source post: 15647271

I believe the heater core access is behind the battery,

Here is another good thread on getting to that mix flap with better pics: https://rennlist.com/forums/996-foru...nt-debris.html My heat is pretty weak so something I will try and fix once I get more motivated. Luckily haven't really needed to drive much this winter but it's on my list of things to address. Also my AC works great.

This is what I see under the battery box. And it doesn't look like any of his pictures.

Quotes source post: 15647615

Follow the two hoses in the upper left, this go to the heater core, it's behind the battery towards the base of the windshield.

Looks like I'm in the wrong area. Going to remove the wipers and hardware first and go on TOP of where the battery was located.

[Image-only post; no author-written text. Original image references:] https://cimg6.ibsrv.net/gimg/rennlist.com-vbulletin/1101x950/core_1_0087dfb03e8111555267b82927b4aa9aa9000ac0.jpg

Getting closer. FYI: You have to remove the Windshield wipers, the supports brackets and the wiper motor. I'm now trying to figure out how to remove this cap and then I will practice yoga and see about getting under the passenger side to remove the bottom latch for this part. Still can't figure out why Porsche would put these holes in this piece to begin with. Some people really enjoy the feeling you get from fixing something yourself. The ability to clear your mind and work on your own car in your own garage. I'm not one of those people.

"The servo is almost in the center with a pink arm on it. Take you pliers and simply squeeze together the connector from the motor to the flap housing and pull off. Then you can take a 7mm wrench and take the nut off that attaches the mix arm to the bottom of the air mix flap. Once the arm is off you can pull out what I'll call a "plug" that attaches to the flap. This is the arm and bottom plug that connects to the flap/door at the bottom." This quote is from a boxter. On the 911 this is certainly not in the center. Anyone have an idea as to how I can get this arm removed and then be able to put it back? Not much room at all to work with.

Wow Red, I take it you're very serious about hot air in your 996! I don't bother with it, that's what my wife is for. hahaha Seriously, keep up the good work and for goodness sakes, don't break anything! lol

Quotes source post: 15649160

It gets cold here in Kentucky. And even on Spring and Fall nights it's a good thing to have. I enjoy driving around with my top down all year long. Heat is needed. Figured that if I fuch things up too bad it won't be worse then what I already have. Worse case scenario I'll divert all water flow from the heat exchange box and only have AC. The GF puts out a lot of heat, and I love it, but she is not always in the car with me. My goal is to finish this project after work tonight. I'll let you guys know if it works. Also. What if I reached down and put tape on the part of the flap that I can see from the outside? Does the smaller half run the heat and the larger the AC?

I'm in the same boat as you, red. Exact same symptoms. Coolant was good, burped the system. Replaced thermostat, replaced radiator. I am ripping my dash out next month to put in a new dash with a glovebox. I'll be taking care of the foam then. I hope that will be the end of the rabbit hole, as there is nothing left to do after that.

Quotes source post: 15649453

I would give that a shot, I'll probably try the same when I get around to it.

For those who aren't great wrench turners (like me) and a little lazy (definitely me), how much will the dealer charge to repair/replace the flap or an independent for that matter. I have the exact same symptoms; polar cold with the AC on but no heat at all.

The blend doors in the underdash HVAC box are what causes the problem. Really have to take the whole dash apart to fix the foam on the blend doors. That being said, my 99 C2 puked all of the foam out the vents years ago and I still have plenty of heat and AC. Of course now with that being said, for a temporary fix (maybe for those cold winter months), wrap the pollen filter in plastic so NO outside air gets in the cabin. That way there is no outside air blended in the HVAC box and all you will get is heat and AC. Put heat on high and push the recirc button so only inside heated air gets recirculated through the system. I've never seen an estimate from a dealer for repair to the blend doors....but since it entails pulling the entire dash apart, I would imagine very big bucks. Even the alternate route of pulling out the heater core to access the one door...well, I don't think a dealer would go that route. They probably would say "we have to replace the whole unit with new". Very big $$$$.

I was given a quote, and it was very high.

Quotes source post: 15652484

I SO wish I had thought of this before tearing into my 911.

Quotes source post: 15652484

To be clear - LOL. Are you saying the filter that's in the frunk near the battery - 1. wrap it plastic 2. heat control on high 3. turn on recirc button And presto - Heat in the cabin It can't be this simple LOL - super curious how you discovered this.

Quotes source post: 15652656

Ummmm....yes. The problem with the deteriorating foam on the internal flap doors is that the blend doors no longer provide adequate flow control from outside air getting into the cabin. The entire mix within the HVAC box is uncontrolled. By blocking the pollen filter, the only source of outside air to the HVAC box, putting the heat on high and recirc will only allow inside cabin air to be recirculated and heated, and not mixed with uncontrolled outside air entering the system.

And it may continue to blow bits of foam into the cabin. Red, you're almost there with this fix. I'm sure you can finish it - you've done most of the hard work already.

Quotes source post: 15653836

will keep this in mind if I every totally loose heat!

Spent a good amount of time trying to reach the bottom of the flapper. Then I did something..... Wish I had done this to start with. I removed the stereo, HVAC computer thing and the upper vent (7 minute job). Then I took a freaking razor blade and I cut a hole big enough for my hand to fit through in the air chamber. I then reached in and taped it up. Then I taped up where I cut the hole. Problem solved. I now have heat. If I had it to do over again I would do as the previous posted said and plugged the fresh air vent.

From looking at that picture, can we see the hole that you taped up? I don't know the location of the flaps and I'm trying to visualize what you did..I may do the same!

Oh my, new thing for everyone to inspect on a PPI - pull the radio and see if the owner hacked a hole in the hvac. Such a sad day...

Quotes source post: 15655423

OP, I'm not one to throw rocks in my glass house, but I think it's important to point out the obvious. I think you should have used a Dremel tool or jigsaw with a short bit. To begin, mark all four corners and make pilot holes for drilling and then spot drill each hole to act as guides. At that point, use a white sharpie to draw four straight lines. Then, with your dremel or jigsaw, cut four straight lines to each corner which will produce a nice square that can be reattached. OP, you should NOT have used just standard black duct tape. Instead, you need 3M high temperature stainless foil tape. (The stuff that HVAC installers use) That black duct tape will goo up over time and the adhesive will not be able to handle the heat and so it will peal off and you'll have the problem all over again. There is also a chance the chemistry in standard duct tape will cause a bad odor when heated. The high temperature foil tape should have been used on the flap as well as the other cut out. I don't mean to be rude to you. I understand you were desperate to find a solution, but this just is sloppy. Sorry. Just my opinion. But I'm glad you got it to work. I'm afraid you're really going to need to at least change out that tape!

Quotes source posts: 15656377, 15656381, 15656416

Cut a hole behind the stereo big enough for your hand to fit through. There are three flaps that you can then get to. I suggest you use better tape then what i did. LOL I knew that this would horrify many of the true Porsche lovers out there. I agree. The black Gorilla Duct tape was what I had in the garage at that time and I had to make do. The truth of the matter is that I have already purchased some foil tape and I may go back in this weekend and re-do my tape job. Perhaps I'll even make use of my GF's smaller hands and see if I can get a much neater coverage. The reason I posted this was to give people another choice. Getting to the bottom flap is going to be a real bear for those of us with a 996. And having to hack apart the top to get to the other side of that flap is no fun either. I'm posting another option. Truth be known I wish I had thought of blocking the fresh air intake and using the recirculate button.

Honestly, if it works and is not destroying the car in a structural way I don't see the issue. Sure it is not pretty and the cut could be done better but it sounds like it works. I might try it myself and see if I could do a cleaner looking job now that we know it works. Since I will use my heat only a handful of times a year IMO it's not worth paying thousands to have the dash removed. I am about to drop some serious coin on IMS, RMS, AOS, clutch and some odds and ends.

Quotes source post: 15657649

+1 While perhaps may not meet certain folks standards, I think the idea is wonderful example of ingenuity. Thanks for sharing Red and being a pioneer

Saving this tread for when I tackle mine. I have been blowing foam for over a year and half now, so its only a matter of time before mine stops. I like red's new method, but I probably wont try that one unless I get really desperate. Does the blend door need to 'seal' with foam? Or will foil tape on the blend door be good enough for its purposes? Does it need the 1" thick foam?

I would give credits to the OP for ingenuity, If you compare it to airbox removal (see here ), this fix is a much less risky. Look at the amount of stuff, screws, connectors, a/c evap to remove.... Also, the access hole can be reused if one need to fix it again or adjust something. If one could make that access hole more tidy and seal it with proper tapes, it's quite a decent option to me.

Quotes source post: 15655423

Desperate times call for desperate measures! As mentioned above, foil tape should have been used...

I like it! I appreciate your methods because that's how I work through many projects and then I learn from others too that offer suggestions/better ideas and then I have the opportunity to go back and address. I am not a mechanically inclined genius, unlike many great owners on this forum, so I read these DIY's.

I like the unorthodox solution. Am I to take it that the silver colored plate (similar in appearance to an outlet plate) is the flap? My question to those that suggest bagging the cabin filter and then operating HVAC in the recirculation mode - have you actually tried this? I would expect defogging/ defrosting windows would be darn near impossible without the introduction of fresh air. De-bagging the filter anytime you want the windows cleared might make one rethink the idea.

The OP was 99% of the way there with a much more elegant and minimally invasive solution when he went in from the top. Bagging that, slicing the enclosure apart and plugging the gaping hole with duct tape is a huge messy hack. It is destructive and inelegant, and devalues the vehicle. I�d be pissed if I found a PO had done this to a car I purchased.

Quotes source post: 15671238

Picture of the whole flap/plate here: https://rennlist.com/forums/996-foru...l#post11478321

Quotes source post: 15671429

So he could have patched all the flaps from the top?

Yup, cut the top of the pivot off with a dremel, remove the plug underneath, unclip the arm on the bottom from inside the car, extract the plate through the hole in the top where the heater core was removed, and recover it with an appropriate material. Any job worth doing is worth doing correctly.

Quotes source post: 15671463

Ah, that's smart. I take that there's only one plate inside the airbox?

Correct.

No reason to cut open the airbox then.

Is that entire plate suppose to be covered with foam?

I think there is more than one door inside the air box but the one accessible from up top is the one that controls the heat/cold mix. And yes that metal door is supposed to be covered in foam.

Quotes source posts: 15671429, 15671442, 11478321

That's unfortunate, if he was that close. I do agree (with others) that this could have been done more cleanly and resealed in a better manner. Every owner has different constraints/ resources / skills. If it were me, I would not be averse to doing something similar had I exhausted, or become frustrated by other options. I would not allow exposed adhesive within the housing, but foil tape and a plate/ plug for the cutout, would likely be my direction. That's because I would not be willing to pay anyone to correct this issue. Resources / constraints include funds to pay for repairs. Red used his skills and resources (creativity) to tackle a problem from a different direction. That to me, is impressive. I can't speak for Red - but my car is not likely to ever be sold. I have never considered resale with any of my cars, ever. Any of my hacks are not going to be seen or discovered by anyone (unless it's my wife or one of my kids). Every owner is different. So those openings look slightly different from what I think I see in Red's photos. I'd like to see a cut-away or parts diagram that shows in detail how it works. Does anyone know of such information?

Installed it is 90 degrees rotated, so the long axis is vertical. It is a blend door, allowing the right mix of heated and cooled air to enter the hvac for distribution into the cabin. This flap is not the item to the left of Red�s picture (that looks like a household electrical outlet), it is the item to the right of that, which he already covered with black gorilla tape. You may need to expand the picture to see it.

Quotes source post: 15671800

I figured the door was shown at 90 degrees. I need a bigger monitor, or better eyes - I did enlarge the photos. Wasn't sure if Red's photos showed the door prior to applying the tape. I did notice what looked like black duct tape toward the right, inside the cut-out. Couldn't make out enough detail to tell exactly what it was covering. That's where a parts diagram would come in handy, at least for me.

For future DIYers, this thread will answer all of the questions so far in this thread. http://986forum.com/forums/performan...nt-debris.html

Outstanding.

Quotes source posts: 15671463, 15671469

There are two plates in there. One to blend hot/cold, one to change level (defrost, dash vents, floor). I just did this repair a couple of weeks ago because the heat in my car was non-existent. Here you can see the cut I made. I used an oscillating tool and a Dremel as the cut got closer to the wiring harness (the picture already shows one hole covered up). This picture shows both flaps. The near flap has four oval holes. The farther flap has 12 round holes! Seven holes to the left of the bend and two columns of five holes to the right of the bend. View of the seven holes on the left, partially covered. Partial view of the two columns of holes. Here is an after shot. You can also see the bottom of the cut in the plastic housing. Actually the plastic piece broke itself off. My plan was to just bend the plastic flap down while I worked but it decided to remove itself as I was bending it. I used the same metallic tape to secure the plastic piece back in place. I taped the entire perimeter on the outside and several inches (as much as I could reach) on the inside. The reattached piece was very solidly attached. Sorry, no pic of that. For me, this solution offered the best results. Going in from the heater core only allows access to one of the flaps. Plus it required cutting parts, possibly damaging the hinge beyond what could easily be repaired. It also requires removing the heater core which could be damaged. I suppose if you were going to replace the core anyway it would be a good partial solution. YMMV. Probably the most "correct" solution is removing the dashboard as documented by Meir on the thread that Ahsia posted. But I'm not eager to remove so many parts and evacuate (and then refill) the A/C refrigerant. The thread that Ahsia posted ( http://986forum.com/forums/performan...-debris-2.html ) was a tremendous help to me, especially post #38 by 78F350. Perhaps going in through the front isn't the most "pure" solution. But I don't have a low-mile garage queen, I have a driver. I also figured that the metallic tape would stay in place and that the repair would vastly improve the ability to heat the cabin. And it is vastly improved!

Not to hijack the thread, but I always wondered why the Porsche engineers put that stupid foam in to begin with. Maybe because they want "some" blending of air through the foam? What do you guys think?

For anyone that has accessed from the top via the heater core, looks like you could tape up that blend door without removing it? Is that the case?

Quotes source post: 15673370

Thanks for sharing, this makes everything a lot more clear. Shame you ruined your car though /s.

Quotes source post: 15673990

I know, right? I love the ruined thing, that's for sure. There's some freedom in having a "ruined" car! Hope my post helps someone. I kinda wished I'd been able to post sooner.

Quotes source post: 15674055

Ha! I am just poking fun. I get both sides of the equation for sure. 99% of the time I am about doing a job the correct way but I've owned so many cars and have done so much work sometimes I just want an easy way lol.

Quotes source post: 15673402

All manufacturers use it. I had the same issue in other cars/trucks.

i did this repair this past weekend...I appreciate everyone's input. I was NOT going to go through the heater core, nor was I going to remove my dash. I thought i was going to have to live with luke warm air forever, even during cold New England winters. This was very easy to do and I was surprised I haven't seen more "how to's" using this procedure. My only question now is, since we are using tape, rather than foam, will that change anything? I'm thinking that we might only get the extreme hot or extreme cold air, rather than being able to set a temp, such as 72 degrees. I'm assuming the foam was there to allow the blending of hot/cold air to come up with a precise temperature. Now that it is sealed, i'm thinking we'll get either hot or cold, with not much in between. Is that true? Is there any downside to the tape? I used aluminum flashing tape from Home Depot....$10. Best $10 i've spent on this car!

Quotes source post: 15673370

Resealing the cut in the vent using tape is interesting. Rather than duct tape, is there any other glue that could be used before the tape? For example, maybe could use some epoxy/jb weld of some sort, then use tape over it? I know foil tape is used to seal most home HVAC systems. I do not know the lifespan of foil tape. Would it be expected to last the remaining life of the car? Lets say 10-20 years?

Quotes source post: 15679319

My experience is that you get what you set it for. If the car is up to temp there is obvious heat coming out of the vents. Once the cabin is warmed up, the temp coming out the vents is appropriate (tepid). YMMV. My thought was that using metallic tape (true duct tape) might cause some noise that Porsche was trying to avoid with dampening properties of the foam. There's also the possibility that the foam hung over the edges of the metal flaps a bit which could create a better seal with the housing. I figured I wasn't going to make anything worse by using the metallic tape. So far I haven't noticed any unusual noises. I'm very happy with the results. I remember reading somewhere that the foam was non-porous, so in effect no different that tape in that respect.

Quotes source post: 15679436

You're probably right, glue or epoxy would work to seal the cut. I actually hadn't thought about that. Getting glue in there without making a mess might be a challenge, but that's probably solvable. To be honest, once I had the metallic tape in place I was surprise at how solid it felt. There was no movement when I tugged on the repaired part. I figure it this way; my house is approaching 30 years old and the metallic tape on the duct work is still in tact, it should be sufficient for this purpose.

Thanks to VW... This is a good video showing a similar fix on a vw. It gives you good ideas about how these flaps work and how they could be patched up literally. You Tube

dup

For us less mechanically inclined. Is there anyone on Long Island ( Nassau / Suffolk counties ) that would do this repair for a fee?..

I was in process of replacing my heater core, and decided to fix that problem "since I was 90% of the way there"....included some "tips" I documented this procedure in this thread: https://rennlist.com/forums/996-foru...the-vents.html