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Hi everyone, first time poster here, please let me know if I'm missing any important information. This is a long one, but I tried to capture as much detail and troubleshooting as possible.
I have a 'new to me' 2014 A8 that has no heat, not even slightly warm at high RPM. I've scoured these forums and Google'd everywhere to try and figure out what the problem might be.
Luckily I have a friend that is an experienced VW mechanic who agreed to look at it with me before I take it to Audi and pay big $$.
We started in VAG-COM by resetting/looking at all the basic settings - fans and vents all work fine and return no faults. You can hear the flaps go back and forth and switch from cool to hot modes.
All the buttons and ***** work fine and switch between A/C (which blows great) and the heat setting with no problem.
The fans blow as hard as you'd expect when heat is on and set to HI with max fan, simply no heat or even warm air.
After troubleshooting the basic settings, the heater control valve sticking closed seemed to be a common problem, so I started there -> https://www.audiworld.com/forums/a8-...-heat-2879579/
I ordered the valve and we swapped in a new 4HO 121 671 D valve but that didn't solve the issue. The old valve wasn't stuck closed and it functioned fine (he has the fancy tool to make it open/close for testing).
We also disconnected the in/out hoses to the heater core and ran water through it both ways. Ran clean, no clogs at all.
Vacuum refilled the coolant and still no heat. That's where I am now.
One of the last things noticed was we confirmed the hose coming out of the heater core is cool to the touch when the car is at temp. Seems to be no flow to the heater core? Where can I find out about the actual coolant flow and inline valves/components potentially creating blockages?
What are my next steps to troubleshoot this thing? He seems to think that if a water pump was bad we'd at least have a little heat at high RPM, but admittedly he isn't familiar with the plumbing in the Audi D4 platform.
Potential clue? The car is new enough to me that I've never used the heat to confirm it ever worked. My wife is the one that reported no heat. I thought it was simply human error with the settings so I played around between auto/manual mode for a bit and confirmed no heat. This is where it gets interesting. After initially reporting no heat and having no heat on chilly mornings for a few weeks, she said it came on mysteriously on one trip home from picking up my son from school and it blew beautifully hot for their ride home. Then, the next morning nothing again. Still nothing. This is one bit of information that I cannot personally verify but I've asked her over and over to make sure it wasn't her imagination - all the kids verify the event. Ugh!
To me that indicates the plumbing is fine? Any thoughts or things to try? Are there other valves that could be sticking closed?
Thanks everyone for looking, appreciate any input.
I'm digging in deeper with my limited knowledge.
There appears to be two of these exact valves in the car and we might have changed the wrong one.
The one we changed was located on the driver side close to the wheel well.
#12 in the diagram below.
4HO121671D #12
I might have made the false assumption based on some other forum threads that this was the heater control valve responsible for flow into the heater core.
#24 in the diagram below- same part, different diagram - is this the one I want? The Audi parts website is a bit confusing and I don't have the service manual (can't find it anywhere online for a 2014). I'm using the web to piece this puzzle together!
Update for the record, I'm going to retract the statement "The car is new enough to me that I've never used the heat to confirm it ever worked."
Going back in more depth to piece together a timeline, I did indeed have it at the tail end of winter and would have definitely noticed a "no heat" issue in New England. I guess it just worked fine and never registered.
So, assume now a summer full of cold AC with no heat use until we turned the dial a few weeks ago and it no longer worked.
The big question to confirm now is if I swapped the wrong valve, or if I'm going down wrong path with that entirely.
I don't know ins and outs of D4 set up, but realize for starters D bodies have two heater cores, not one. One for each side. Thus expect to find either two valves, either as separate parts or as one integrated unit. D3 was a single unit that had both valves in it.
Also if you pull the valve, you should try to blow through the core for the relevant side(s) to be sure it isn't clogged. I recall several D3 owners over the years (and with more miles) finding badly clogged cores. Sometimes they could just back flush them by running water through in reverse to get the crap out to restore the heating function much better.
I’m having the same exact problem on my 13 a8l 4.0t. I’m thinking air got trapped in the heater core. There’s a screw on the coolant lines running to it to bleed it under the plastic under the hood behind the engine (I believe it’s called the plenum). Haven’t got to try it out yet but I will do so Saturday once i receive some coolant in the mail cause I was all out and didn’t want to risk not having any replacement to top it up
Hi everyone, first time poster here, please let me know if I'm missing any important information. This is a long one, but I tried to capture as much detail and troubleshooting as possible.
I have a 'new to me' 2014 A8 that has no heat, not even slightly warm at high RPM. I've scoured these forums and Google'd everywhere to try and figure out what the problem might be.
Luckily I have a friend that is an experienced VW mechanic who agreed to look at it with me before I take it to Audi and pay big $$.
We started in VAG-COM by resetting/looking at all the basic settings - fans and vents all work fine and return no faults. You can hear the flaps go back and forth and switch from cool to hot modes.
All the buttons and ***** work fine and switch between A/C (which blows great) and the heat setting with no problem.
The fans blow as hard as you'd expect when heat is on and set to HI with max fan, simply no heat or even warm air.
After troubleshooting the basic settings, the heater control valve sticking closed seemed to be a common problem, so I started there -> https://www.audiworld.com/forums/a8-...-heat-2879579/
I ordered the valve and we swapped in a new 4HO 121 671 D valve but that didn't solve the issue. The old valve wasn't stuck closed and it functioned fine (he has the fancy tool to make it open/close for testing).
We also disconnected the in/out hoses to the heater core and ran water through it both ways. Ran clean, no clogs at all.
Vacuum refilled the coolant and still no heat. That's where I am now.
One of the last things noticed was we confirmed the hose coming out of the heater core is cool to the touch when the car is at temp. Seems to be no flow to the heater core? Where can I find out about the actual coolant flow and inline valves/components potentially creating blockages?
What are my next steps to troubleshoot this thing? He seems to think that if a water pump was bad we'd at least have a little heat at high RPM, but admittedly he isn't familiar with the plumbing in the Audi D4 platform.
Potential clue? The car is new enough to me that I've never used the heat to confirm it ever worked. My wife is the one that reported no heat. I thought it was simply human error with the settings so I played around between auto/manual mode for a bit and confirmed no heat. This is where it gets interesting. After initially reporting no heat and having no heat on chilly mornings for a few weeks, she said it came on mysteriously on one trip home from picking up my son from school and it blew beautifully hot for their ride home. Then, the next morning nothing again. Still nothing. This is one bit of information that I cannot personally verify but I've asked her over and over to make sure it wasn't her imagination - all the kids verify the event. Ugh!
To me that indicates the plumbing is fine? Any thoughts or things to try? Are there other valves that could be sticking closed?
Thanks everyone for looking, appreciate any input.
The problem was addressed by replacing the water pump. ???
That is at least what the bill showed today from the Audi dealer. This is very surprising to me since the engine temperature gauge never indicated an overcooled or overheated engine.
After past warranty repairs for this car I am getting the impression that the bill doesn't always state what really was fixed.
That is at least what the bill showed today from the Audi dealer. This is very surprising to me since the engine temperature gauge never indicated an overcooled or overheated engine.
After past warranty repairs for this car I am getting the impression that the bill doesn't always state what really was fixed.
Do you by any chance know the part number that was changed? Should be on the paper
10-25-2017, 06:09 AM
No Heat in 2014 A8 4.0T
