Fellow forum goers, present and future, I bring to you information regarding heater core replacement should you ever encounter this daunting task yourself. Embarking on this task has proven fairly educational for me and I'm going to share what I've learned from it for future reference to any who need it. Now, for those reading this, I have an issue at hand that I need some suggestions on, so if you don't want to read all the writeup of the core replacement, feel free to scroll down below the pictures to read about the current issue at hand and chime in if you have any suggestions

First and foremost, getting to the heater core (herein further referred to simply as "the core") is not all as bad as it might sound when you first are told that it involves removing the entire dash. Its a pretty straightforward process achieved by first removing the faceplate of the HVAC controls and proceeding to remove the rest of the center console. After that, drop the glove box and undo the wiring harnesses, fuse panel and relay panels from under the driver's side. You shouldn't have to actually unplug any of the wires, just unbolt the harnesses from where they're being held. After that, the steering wheel gets dropped and then there are four, 15mm bolts that actually hold the dash to the firewall. Once those bolts are out, the whole dash should be able to be pulled towards the rear of the car far enough to access the core, which is secured by two screws. Also, make sure to empty the A/C refrigerant lines and remove them from the firewall as well as undo the hoses connected to the in/out of the core. This is about how it should look before you undo the 15mm bolts holding the dash to the firewall:





After you get the new core installed, you will want a minimum of three people to help start putting everything back into place. The reason for this is because the dash isn't very light so you'll want two people on either side of the passenger compartment to push the dash back towards the front of the car and the vital point: a third person looking in the engine bay to make sure the in/out lines from the core make it through the hole in the firewall successfully. Here's a shot of the size of the hole the in/out connections for the core have to get through to be connected to the rest of the cooling system:



And here's a shot of what will happen if you don't have that third person making sure that the connections are indeed coming through that hole without issue:



And here's what the old core looks like; its quite apparent that this is in fact the cause of my loss of coolant and buildup of vaporized coolant on the inside of the windows. As you can see, the connections themselves are shot, causing it to leak down the firewall, and down towards the bottom (close up in the shot below this one) all the corrosion of the main surface area of the core is how it was getting in the vents.






Now, the current issue at hand. After everything was reassembled and plugged back in where it belonged, another issue cropped up that I hadn't expected. We reconnected the battery to proceed to test that everything was working and all the lights came on, the stereo played music, the windows rolled up and down, power seats moved, all was good. Went to crank the motor and nothing happened. No sound of the started motor cranking at all, no clicks, nothing. Rechecked all the connections and still nothing.

Now, I've already had ImTheDevil on the phone to get some preliminary input and we've concluded that its very likely that I've encountered a coincidental failure of the ignition switch, seeing as all the other electronics work and upon turning the key to engage the crank position everything *stays* on, signaling that the ignition switch isn't tripping the relay that deactivates all of the auxiliary components to ensure maximum current flow to the starter. Based on this information, does anyone have any other suggestions of what might be causing the motor to not crank, or do you all agree that the ignition switch has reached the end of its days, being a notorious part for failing?

And so concludes the saga of a heater core replacement. Thank you all for your input on how to get the vaporized coolant off the windows, any potential input on how to resolve my cranking issue, and as soon as the cranking issue is resolved, I'll be back on the road with a functioning heater again Good luck to anyone in the future who has to replace a heater core, hopefully this post can be of some assistance to your endeavor.

 

Conculsion if it was working before than it should work again. therefore i say a harness did not get pluged in all the way

 

that looks like more of a pain in the *** than a big turbo install

 

Yea, we thought about that too, hence pulling everything back out to check it all and nothing is loose, nothing is dangling, every wire under the dash is connected to something. Devil had a good point too, most of those harnesses control multiple things, not just one single point IE the ignition switch and he pointed out that since every single other electrical function is working that it is not likely that something is not plugged in somewhere; but I appreciate the suggestion

 

and you make a soild point in the previous post that things do turn on but the engine does not turn so it might be switch but i guess you wont know until its replace i would take of some parts and put a flashlight in the dash and double check it might be a possibility

And remember just because the harness is plugged in and works doesnt mean its plugging in 100%

 

Yea, fortunately ignition switches can be had on the cheap so I don't feel too put out about replacing it. Who knows, if it is in fact functional and we do find that something else isn't quite connected all the way, who's to say the ignition switch has ever been replaced before and being a notorious part for failing isn't near its end anyway so I'm definitely replacing that and hoping for the best and if that doesn't fix it well, at least I have a new ignition switch in there haha

I should note that a synapse fired recently that may give some more credit to it being the ignition switch. I got thinking about it after Devil mentioned the function of the relay that interrupts the auxiliary components when the key is turned to the crank position and what he said about how the lights and stereo and other electrical components are momentarily shut off to divert maximum power to the starter to crank the motor and I recalled that there have been a few times in the last couple months when I would park while waiting to pick up my friend from work and turn off the motor but leave the radio going and upon restarting the motor, the radio didn't shut off but other times under the same circumstances it would turn off when restarting the motor.

Now, not *fully* understanding the mechanics of starting and restarting the motor and the associated electrical function, it could be possible that restarting doesn't require everything to be shut off, however, if its managed by the ignition switch telling that relay to bypass the auxiliary components, it doesn't seem logical that a restart as opposed to a cold start would affect whether or not that relay is activated so I'm wondering if the switch has been progressively starting to fail, every once in a while getting stuck open and not activating that bypass relay allowing the radio to stay on when cranking and the process of having the steering column on the floor for the removal of the dash to get to the heater core gave it its last jostle and caused it to finally stop functioning. Does that sound likely? Has anyone else ever been able to crank the starter without the radio being interrupted?

 

What'd you do about the broken tube on the new heater core?

 

Got another one haha napa had one for about 5 bucks more than I paid through ecs so we just got it from them and made sure to have that third person spotting when putting that one in.

 

Car is still out of commission. Didn't want to wait for shipping on the ignition switch so my buddy that's been helping me with this project who works at a dealership called up his sister dealer that sells Audis which is about 25 miles south of my city and because it was a dealer to dealer sale, he got discounted OEM parts so he gave them the VIN to ensure they sent the right part since there's a VIN split from 97-98 on the ignition switch and what do they do? Yea, you guessed it, they sent the wrong one. How they fuct that up is beyond me since they had the fvckin VIN to cross reference so now I've got to wait for them to send up the correct part, this time guaranteed to be accurate cuz we pulled out the original one (obviously, as that's how we discovered the one they sent us was the wrong one) and took the part number off that one so if they somehow mess it up again I'm going to flip my lid at these guys lol

I probably wouldn't be as pissed if I knew for sure that the new switch will get my car running again but right now I'm more or less banking on getting the new one in there and hoping for the best (Devil, I know you told me how to verify using an Ohm meter that the old one wasn't connecting but we forgot to check the terminals before completely taking it out of the steering column to get the part number off it to order the right one and now its unpowered and my buddy's got a wedding tomorrow so we won't be messing with it again til Saturday, which by then the new, correct part will be here and we might as well just put it in and see what happens since the other one is already out. Poor call on my part I know, I should have remembered to prod at it before taking it out, but too late now so I guess I'll just deal with it) But yea, so I just wanted to vent a little at the incompetence of some people's ability to use a computer and a supplied VIN to get the right parts ordered and whine a bit about having gone a full week now without being able to drive my car cuz of all these petty setbacks on what should have been a six hour job. Thanks for listening lol

 

Crap. Go figure. I saw that your thread was updated and was hoping the car was fixed and you'd be posting about driving again. When it does arrive, I hope it is the switch. Unless there's a broken wire in a harness somewhere or the damn crank sensor decided it was time to die, I can't think of another reason that it would just quit working. Crossing my fingers!