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Wednesday, December 6, 2023

Doug's Domain

Doug Vetter, ATP/CFI

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Friday, July 24, 2015

HVAC Overhaul Plan

Reports of my death have been exaggerated. Rest assured -- I'm still here but quite busy with stuff unrelated to BMWs.

Of course I have been thinking about the next step in the E36's restoration process and recently made the decision to have my technician do the next phase, as it involves equipment and skills I lack and have no immediate desire to acquire. And then there's my crazy schedule. I simply can't justify the time and mental effort needed to tackle a job of this magnitude right now. I'm hoping I can get back in the game next year for the engine overhaul but time will tell.

My goal is to have my technician:

  1. Replace the carpet, hopefully without cutting. This involves removing the dashboard, which is being done to facilitiate the remaining items rather than avoid cutting the carpet specifically (but that's certainly a perk since the goal is to make it look factory original).

  2. Replace the heater core. It's original, and given that the end caps of the core are (unfortunately) plastic, I'm absolutely amazed that the thing hasn't sprung a leak in the last 17 years. As I mentioned when I purchased the carpet a few years back it was one of the few remaining in worldwide BMW inventory. I have no idea whether they've done another run of them or whether they're ENDED at this point, but I sure as hell wasn't going to install a new, potentially irreplaceable, carpet only to have it soaked by engine coolant from a failed heater core.

  3. Replace the HVAC Controller. Yea, you read that right. Unfortunately my unit's LCD recently started to delaminate, exposing more of the backlight. This is a failure mode I've never seen before in the E36, but probably because the unit installed in the car has been in service longer than the original one I (stupidly) threw out before I knew how to apply the capacitor fix to address the more common failure mode of power supply irregularities (display flickering).

    This unit is only available remanufactured at this point and I wasn't happy to hear that because I know all too much about electronics. My technician attempted to allay my fears by suggesting that the display failures are common and all the remanufactured units likely have a new display. That didn't make me feel any better for unloading the better part of $500 + a $200 core. It should be half that at most simply because it's not new.

    The units also come uncoded, so it makes sense to do this while the car is in his bay for other purposes. Of course I did ask if he could code it quickly for me last week but the news is BMW has once again replaced my dealer's programming systems with models that don't particularly like to talk to the older cars. He added that the problem is of sufficient concern to BMW that they are paying techs a bounty for finding bugs with the system in conjunction with the older cars. If their case is picked they get the bounty and have a chance at an annual award as well. Bug bounties on BMW diagnostic software -- clear evidence of BMW's long term plan to push all the system testing out to the customers and technicians. No sense in paying qualified developers in a properly equipped lab to do that job, right? *Sigh*.

  4. Replace the A/C evaporator core. I debated doing this for obvious reasons (it's about twice the price of the heater core, which was actually quite reasonable as far as BMW parts go), but justified it as a "while in Rome" fix.

  5. Replace the A/C compressor / clutch. Ever since I made the mistake many years ago of running around with an inoperative aux fan the A/C compressor has always made a kind of annoying rattle at idle. Thinking the rattle was caused by the A/C pulley and hydraulic tensioner I had my tech replace those components (this was a LONG time ago, back before I really assumed most of the responsibility for working on the car) but the problem remained. I have lived with it for years but no longer.

    While it won't be news to anyone familiar with the E36, BMW used to provide compressors from two different companies -- Nippon-Denso and Seiko. I recall learning a long time ago that my car was equipped with a Denso unit but I couldn't recall for sure. Given the option of two compressor makes and the fact that the compressor must be matched to the expansion valve I assumed I'd have to get my lazy butt under the front end and pick off the part number.

    But then I learned from my parts guys last week that the Denso unit is no longer available and the part number has not been succeeded. The upside, I suppose, is that had I needed a Denso unit only remanufactured versions were available. But the Seiko units BMW is selling now are new units. And they damn well better be given what I'm paying for it. Even with my substantial discount this one hurt.

  6. Replace the expansion valve. This is being done for two reasons -- first, because the part is a mechanical device rather than a fixed calibrated orifice as I originally surmised and according to my technician subject to wear, and second, because this would ensure we have the correct expansion valve installed for the new compressor. The part is relatively inexpensive so it seemed like a rational thing to replace.

  7. Replace the A/C Dryer. The dryer is supposed to be replaced anytime the system is opened, or left open for a considerable time. And my system would definitely qualify because I was forced to run around for a week or so back when the condensor sprung a leak before I could get on my technician's schedule. The part isn't exactly cheap but it's not that bad either so this was easy to justify.

  8. IRAN the HVAC airbox, which I have noticed, particularly in the winter months, tends to make a "cracking" sound as the air doors open once coolant comes up to temperature a few minutes into the drive. I haven't heard the noise lately, which is bound to make troubleshooting more difficult, but it should be easy enough to play with the system manually to track down the culprit.

    When I asked my technician about the possibility of replacing the seals on the doors he said they are molded into the doors and not intended to be replaced so if replacement really turned out to be the only option I'd likely have to buy a new airbox. I'll spare you the price on that -- you can look it up if you really want to experience the sticker shock -- but I will say that it turned out to be a moot point. The unit is apparently now made of unobtainium.

    The parts guy told me that it isn't discontinued but there were none in worldwide inventory and the availability date was November 2015....and that date had been previously pushed back from February. Needless to say I won't be ordering one, but at least pulling the dash will give my tech the opportunity to inspect my unit. The absolute worst case scenario is that we have to pull the dashboard again at some point.

After discussing the plan with my technician he told me to gather up all the parts and I began that process a few weeks ago. The last components are coming from Germany and have a 2 week ETA.

Once the remaining parts arrive I'll set up a time to deliver it and let my tech get started on what he's estimated will be a three day adventure...assuming of course he gets three consecutive days to work on it. The guy eats his lunch on the run and is interrupted constantly (yea, even by annoying E36 geeks). I feel bad for him, but that's what you get for being the leader of the shop and the go-to guy. While I don't doubt his total time estimate my guess is the car will be out of my hands for at least a week. And it's probably just as well as I haven't driven the E46 at all since I installed the new tires so I'm looking forward to that.

Updated 8/2/2015: The compressor and expansion valve have arrived. A reader pointed out Denso-branded compressors are available on Amazon for a steal. Unfortunately they appear to be Chinese ripoffs manufactured under license from Denso. Buy that if you want but I'll stick with the Japanese made OE parts.

Mileage: 260500