NEED HEAT HELP

[Brendanlotzer]

So as the title states my heat is acting up.
To start a timeline....

About a month ago it didn't work on my trip to work or to home. Next day and for the next 3 weeks after everything worked great. 3 weeks later same thing happens. Then this week it won't work at all.

This is what I have done so far to try and remedy the issue as well as some diagnosis that can hopefully help someone lead me in the right direction. So I started by looking for leaks. When I found no leaks I decided to try and "burp" the system because I figured well an air bubble getting caught may be the cause. I attempted burping it by opening the overflow tank cap and waiting until I saw no further bubbles. Frankly there weren't many bubbles. Check heat -- none.

So today, I decided to dig deeper. I started the car, and then waited until it was up to temperature. Feeling the heater core hoses, one was hot, one was not. I remove the return line, and in fact there is no coolant going through the line. Okay great heater core must be plugged. So I let the car cool down and then I let some coolant system flush stuff from the auto parts store sit in the heater core for about an hour. Hook up the hoses and wash that sucker out. Looks clean as could be. Water is flowing through no problem.

Hook everything back up after refilling coolant and flushing water out of heater core. Start the car, get it up to temp, (all while burping system/ unless I am doing that wrong in someway). Still nothing. Feel heater core hoses, nothing. Cold.

Any idea what could be going on here? I'm lost. Winter is coming. I have an hour drive each way to work each way and pretty soon my heated seat isn't going to do the trick. Thanks in advance for any help.

[Stazi]

You might need to apply a vacuum to the outflow hose to get it to properly burp. Try burping it on a steep incline as well, nose up.


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[A4x]

Check codes. If the HVAC heater blend door is not opening then no cabin air can be directed over the heater core. This should set a DTC.

[mtroxel]

If you have no heat on the return hose, and it sounds like you're sure there's no blockage in the heater core, I'd look at the valve in the heater hose. If that's turned off, you aren't getting heat no matter where the blend door is. Because its German, there are a few versions of it in the repair manual. Mine is vacuum controlled. as in diagram A. If yours is too, I'd check that vacuum hose, hell they're cheap maybe just replace it. I might even go to the junk yard and buy another valve.

I know Eau Claire, it gets damn cold there....real soon. Get to it!

[Smac770]

Is it a B8.0 or B8.5? B8.0, the coolant shut-off valve is vacuum actuated. B8.5, it's electrically controlled.

[Brendanlotzer]

If you have no heat on the return hose, and it sounds like you're sure there's no blockage in the heater core, I'd look at the valve in the heater hose. If that's turned off, you aren't getting heat no matter where the blend door is. Because its German, there are a few versions of it in the repair manual. Mine is vacuum controlled. as in diagram A. If yours is too, I'd check that vacuum hose, hell they're cheap maybe just replace it. I might even go to the junk yard and buy another valve.

I know Eau Claire, it gets damn cold there....real soon. Get to it!

I have the B8. It has what looks to be a vaccum actuated valve. I was also curious if that could be the problem.

- - - Updated - - -

No codes for HVAC.

[Brendanlotzer]

Would hooking a suction gun up to it be equal to applying a vaccum to the outflow hose?

[mtroxel]

Would hooking a suction gun up to it be equal to applying a vaccum to the outflow hose?

Probably. But I'm not entirely sure how it works. This is from the ElsaWin manual:

The Climatronic Coolant Shut-Off Valve - N422- -B- is briefly activated, for example, by the Climatronic Control Module - J255- A/C display and control head to check function (without the function being required) in certain intervals (for example, after 20 engine starts). If the vacuum hoses are incorrectly connected to the Climatronic Coolant Shut-Off Valve - N422- -B-, then the coolant Shut-Off valve -A- is activated briefly. If the hoses are interchanged, the vacuum will remain in the vacuum hose vacuum diaphragm -A- for an undetermined amount of time after the activation is completed. The Shut-Off valve -A- will not open. Coolant will flow into the heat exchanger and the A/C system will not heat when the Shut-Off valve -A- is closed.

Confused? Me too. And from this note, I get the impression it only shuts off the coolant to help the motor get up to temp:

The Climatronic Coolant Shut-Off Valve - N422- / Coolant Shut-Off Valve - N82- is then only activated, for example, via the A/C system controls (either directly or via the engine control module) when the A/C system is set to “OFF”. The engine RPM must be lower than 5,000 and the coolant temperature must be below 90 °C (194 °F). Shutting off the coolant circuit to the A/C heater core accelerates the engine warming upwhen the coolant is cold.

So another way to test it would be to take it out of the system, patch those two hoses together with some hose clamps and a little copper pipe and see if you have heat.

If you have VCDS, I know there's a test for it in the output tests. I think it throws a code there too.

[Brendanlotzer]

Probably. But I'm not entirely sure how it works. This is from the ElsaWin manual:



Confused? Me too. And from this note, I get the impression it only shuts off the coolant to help the motor get up to temp:



So another way to test it would be to take it out of the system, patch those two hoses together with some hose clamps and a little copper pipe and see if you have heat.

If you have VCDS, I know there's a test for it in the output tests. I think it throws a code there too.

Hmmmm thats interesting. I appreciate it. Yeah I'll probably try throwing a "patch" in there tomorrow and see what happens. That's a good idea. Thanks!

[Smac770]

The cut off valve is supposed to prevent heat redirection from the engine until the coolant reaches sufficient value (I assume this to be the ENG105715 value, which roams around in the low 60s C on my car). You can see the block diagram of the coolant routing I modified from the Audi doc here: https://www.audizine.com/forum/showt...1#post13778760

If you have the vacuum actuated one and a vacuum gauge/hand pump, it should be easy enough to test. I don't know if the valve is vacuum activated or vacuum deactivated. You can see more about the vacuum line routing to it here: https://www.audizine.com/forum/showt...m-Hose-Routing
Pull the line off the valve and put it on a gauge and see how much vacuum is coming to the gauge at start and then after the coolant has warmed up to normal operating temp. I would expect at some point the N422 control solenoid is activated and the vacuum is passed through to the line, or it could be vice versa.
Then you can plug the line and use the vacuum pump to start with no vacuum, expecting then no heat, and then apply the amount of vacuum you saw from the engine and then hopefully now feel heat.
This of course assumes the problem is not elsewhere in the heat exchange, thus best to start with mtroxel's test of no valve in the loop at all.
So you might have an issue with the N422 solenoid or the shutoff valve.

As for bleeding the system, the Audi HVAC repair manual says to pull the return hose (the right side one, as in right side of the car, not your right side as you stand at the bumper looking back at the firewall) forward exposing the bleed hole on the pipe (this is at the firewall junction, under the plenum cover behind the jump start block). Then pressurize the overflow tank to push coolant into the system. All air is removed when coolant starts to flow from the bleed hole. Slide the return hose back on and resecure. Then repressurize the system (1.0 bar) to check for leaks. If all good, top off the overflow tank as necessary and you're done.

The repair manual mentions "When bleeding coolant circuit, take special care to ensure complete bleeding of heater cores. If there are still air bubbles in the heater core, it may cause the customer to complain of insufficient heating performance in winter or different air temperature from vents at same setting in regulated mode." It also mentions to be sure not to get the coolant pipes swapped. The exchanger doesn't work well with the coolant going the wrong way.

The Audi tools for that would be the cooling system tester VAG1274B (https://audi.snapon.com/SpecialTools...temId=19150195) and the appropriate adapter for the overflow tank (https://audi.snapon.com/SpecialTools...itemId=9640195). The leak test procedure says to pump to 1.0 bar, so I assume the same would be sufficient for the bleeding process. For testing the cap, it's adapter https://audi.snapon.com/SpecialTools...itemId=9650195. The pressure relief valve in the cap is suppose to activate at 1.4-1.6 bar.

One comment on the leak detection process, the manual does say be at operating temperature. I'm not sure you'd really want that for the bleeding process though.

Coolant flush and fill, the filling process is done using https://audi.snapon.com/SpecialTools...?itemId=120163 . Compressed air is used to build a vacuum in the coolant system, which then sucks the coolant in. This allows for not needing to bleed the system, though I notice the bleeding process is still in the filling process in the Engine Mechanical repair manual - Coolant system section. Better safe than sorry. After filling, bleeding, you then run the engine, A/C off, temps set to Hi, for 3 minutes at 2000rpm, then idle till radiator lines are warm, then 2 more minutes at 2000rpm. Then top off the tank once everything is cold again, if necessary. Damn.

[Brendanlotzer]

So an update.

I replaced the vacuum pump (N422) with a straight valve to diagnose if the problem was the valve or not. Burped the system through the return line on the heater core. The heat worked. So then I put the N422 back on, burped the system again and the heat worked! So great, all is fine and dandy. Drive it for a week, it's nice, it's warm, everyone is happy. Then of course I have a drive to Duluth last night (2.5 hours) and it's 32 degrees out and the heat quits working again even though it worked on my way to work yesterday morning.

My thought is that there is air getting in the system somewhere even though, if I'm losing coolant somewhere I can not see it anywhere on the ground and the overflow tank looks to be at exactly the same level. It's just so odd to me that it can work perfectly, like I'm talking HOT, then 8 hours later after it sits in the parking lot at work I get nothing. Not even warm air.

I'm going to try burping and filling the system as Smac770 described (thank you btw). This car is going to be the death of me before the end of this year. Haven't gone more than 2 weeks without a problem in 2019 with this car, and now it's got a B8.5 motor in it haha.

There are still no codes for HVAC. I do have a code for the Intake Runner Flaps (not the right name but I think you'll understand). I replaced the manifold and the code is still there. I also replaced the vacuum pump thinking maybe there wasn't enough vacuum in the car which could cause that N422 valve to not function but it seems like it worked fine for the last week so I doubt it'd be this intermittent since its just a vacuum controlled diaphragm essentially. I'm not sure why but I still have that code. I'm going to have to keep digging around but that's for another thread.

[mtroxel]

Well, you've learned a lot. The heater core is fine, and when you get hot coolant flowing you have heat. I don't know about your air bubble theory. I'm a pretty limited sample size, but I've owned two 2.0T motors now (both pretty much the same block and cooling system) and have found they are easier to burp than some other motors I've worked on. I think you've got a bad N422 valve, and taking it off and messing with it freed it up temporarily.

When you say there are no codes for HVAC, are you using VCDS? And if so, did you know there is an output test for N422?

[Smac770]

Keep in mind there's two devices in the vacuum path. There's the N422 solenoid which the car switches to pass vacuum to the valve, and then there's the actual valve. It very well could be the N422 solenoid is getting temperamental with the cold. There's an identical solenoid that connects the vacuum pump to the intake manifold runner control valve. :-)

When it stopped working, I would have disconnected (and plugged, don't want an intentional vacuum leak) the vacuum line from the valve and and experimented with the vacuum levels and tried manually actuating the valve to see if heat would start flowing. You need to determine which device in the vacuum control path is actually failing. I'd bet more on that path being your problem than air leaking into the coolant system. Unless you're actually venting air during the bleed process, then yeah.

Maybe put a T on the vacuum line from the pump and watch the gauge and see what goes on with the vacuum level as you drive around (or better yet, as someone else drives around).

[Stazi]

Wait, if he is having an issue with the solenoid that controls his heat and also he is having an issue with the intake manifold control and they are both connected to the same vacuum source then I would suggest that maybe there is something wrong with the vacuum source and not the solenoid‘s because those are both connected to the same common item.

I agree, he needs to check to see if he is losing vacuum which is then attributed to the fact that he is getting errors with his intake manifold control and also that the hot water isn’t getting to his core. I find it hard to believe that the vacuum is OK and that two solenoids that runoff the same vacuum as suddenly both faulty. It makes more sense that the most common element to both problems is the real source of the underlying issues.


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[Brendanlotzer]

Well, you've learned a lot. The heater core is fine, and when you get hot coolant flowing you have heat. I don't know about your air bubble theory. I'm a pretty limited sample size, but I've owned two 2.0T motors now (both pretty much the same block and cooling system) and have found they are easier to burp than some other motors I've worked on. I think you've got a bad N422 valve, and taking it off and messing with it freed it up temporarily.

When you say there are no codes for HVAC, are you using VCDS? And if so, did you know there is an output test for N422?

Unfortunately I do not have VCDS no. Just a regular scanner that I've used for all my vehicles. I know I should have VCDS and I know how helpful it could be, just the funds haven't been there with all the other problems I've had this year.

[Brendanlotzer]

This is why I mentioned the intake issue because my head went to the same place thinking possibly a vacuum issue.

Can someone point me in the direction of the best spot (if there is) of where to check for vacuum loss?

Thank you.

[Stazi]

Find the line that goes to these valves., cut and insert a “T” and then connect to. Boost/vacuum gauge and route it up with a long hose into you cabin, making sure not to kink the hose, and then monitor it while you drive to see the the vacuum disappears.

Now, I’m not sure if the vacuum sauce is in anyway connected to the intake manifold, because if it is and your car is turbo then there will be periods where you go into boost instead of vacuum.

I would hope that based on the way that these systems work that they are not at all connected to the charge air system and that they have their own separate vacuum system that is connected to the vacuum pump, so that they are always seeing vacuum.

Now, if you end up seeing that you are losing vacuum then you have to determine whether is there a hole or crack in a hose somewhere or is your vacuum pump Jacked


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[Brendanlotzer]

Find the line that goes to these valves., cut and insert a “T” and then connect to. Boost/vacuum gauge and route it up with a long hose into you cabin, making sure not to kink the hose, and then monitor it while you drive to see the the vacuum disappears.

Now, I’m not sure if the vacuum sauce is in anyway connected to the intake manifold, because if it is and your car is turbo then there will be periods where you go into boost instead of vacuum.

I would hope that based on the way that these systems work that they are not at all connected to the charge air system and that they have their own separate vacuum system that is connected to the vacuum pump, so that they are always seeing vacuum.

Now, if you end up seeing that you are losing vacuum then you have to determine whether is there a hole or crack in a hose somewhere or is your vacuum pump Jacked


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Alright. Cool thanks. Yeah I already sprayed all the lines and around the vacuum pump with carb cleaner the other day when I had this thought but I still could have missed it if there was a leak.

It is a turbo'ed 2.0

[mtroxel]

Brendan, you aren't coming my way any time soon are you? If so, hit me up I'll put my VCDS on it. But I too had thought of the chance the intake error and the N422 issue are related to the same vacuum source.

[Brendanlotzer]

Brendan, you aren't coming my way any time soon are you? If so, hit me up I'll put my VCDS on it. But I too had thought of the chance the intake error and the N422 issue are related to the same vacuum source.

Sent you a PM.

[Smac770]

I wouldn't go spraying carb cleaner around an engine with as much plastic as exists on these engines, such as the plastic bodies of those solenoids.

If you don't have the vacuum/pressure pump/gauge, I suggest getting one. It's very useful. Same for VCDS. Pretty much a royal pain to troubleshoot these cars without that. I have the Mityvac stuff, plastic MV8000 vacuum only kit (https://www.amazon.com/dp/B00265M9SS) and the metal MV8500 vacuum/pressure kit (https://www.amazon.com/Mityvac-MITMV.../dp/B0002SQYUA). It's been helpful to have both, as well as the connecting parts for testing. Definitely don't go "cutting" any lines, you can hook up the gauge with the included accessories. Also have a long 10' vacuum line that came in a cat backpressure kit so I can hook the gauge into wherever but then watch it as I drive around (as long as I don't mind having the driver window down to run the line into the cabin).

The path of interest I've already documented in the vacuum thread I already linked earlier. Branching of the vacuum lines at the pump, a y-pipe goes high behind the engine and connects to the N422 and to the N316. So test the vacuum sourcing into the y-pipe and coming out of both solenoid ends of the y-pipe. Basic follow the carrot, but you can't do anything without the tools.

[Brendanlotzer]

So thought I'd give a little update. I took out the vaccum controlled valve for theory testing. Sure enough, with my patch pipe that just connects the two heater core hoses has worked. I have had heat for the past 2 weeks everyday.

I bought a turbo/vaccum gauge. So I will get that hooked up but I'm going to assume I have a vaccum issue based on all the signs pointing toward that as discussed above. I have an old vacuum pump off my old motor to swap, so if it's that at least it will be a free part.

Thanks for all help so far in this process. It's 9 degrees today so at least I'm warm for the time being.

[Stazi]

I called it!!


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[mtroxel]

I called it!!

Don't I get credit for a 1/2 a sack for suggesting he put a test pipe in the heater hose?

[Brendanlotzer]

Definitely a team effort! Haha. Again thanks to you both as well as the others in this post who have been along on the ride.

[Brendanlotzer]

So update. I'm dumb. This whole time I think it was my fault. I did some searching today to find a vacuum leak. Couldn't find anything. I did more digging and I think I had the vacuum lines backwards on this valve. https://www.ecstuning.com/b-genuine-...ch/037906283c/

I switch those around. My heat now works. The idle is smooth. And I don't have a check engine light. Thank you all for you help. I learned even more about this car through this so that's always appreciated. Happy new year!

[audibooster]

Hey all, My engines top end (Chain Tensioner failure) was rebuilt from the private dealer we bought it from and It seems i have the same issue as Breadanlotzer. Same issue of heat from time and yes a check engine light.
I've also done the heat core flush (Both forward and reverse flow) and the heat works for a few days and then it doesn't I stumbled upon this post.
My 2011 B8 A4 has two of those those Solenoid Valves (037 906 283 C).
Does any one have a diagram and or pics of how they are connected. I want to make sure that the lines are not switched around. Wonder if the dealer hook them up wrong.
Thanks

[mtroxel]

I could go out and take a picture of my 2011, but it would take the same amount of time for you to just swap the two vacuum lines on your 2011.

I'm lazy.

[audibooster]

I know but i have two of those solenoid valves. One from that heater switch and one from the intake manifold but the two are connected.

[Smac770]

https://www.audizine.com/forum/showt...m-Hose-Routing

[askin]

Once again I owe this community my sanity. This thread saved me from fixing a problem I didn't have. Was hard driving trying to bleed cooling system. Was about to get the hose back out in freezing temps and CLR the heater core this weekend because no coolant coming from return. Ran all the diagnostics that AFAIK told me what I already knew. Two+ hours to change water pump. 10+ hours trying to get heat. And just needed to switch those vacuum hoses.

Thank you from me, my wife, daughter who is about to start driving this car, my coworkers, and the many many people in my community that I didn't NASCAR rage bump off the road today.

To be fair, prior owner had used crap coolant so won't be surprised if the entire cooling system falls apart at some point. Now to front suspension. Praying that the continual Deep Creep from the past month has worked a miracle on the upper control arm pinch bolt. Maybe the delayed few days and changing temps is providential? Thanks again!