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Saturday, April 19, 2014

Doug's Domain

Doug Vetter, ATP/CFI

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Sunday, December 5, 2010

Fog Light Bulb Replacement

One of the more annoying aspects of winter in the Northeast is that the days are shorter and I inevitably wind up driving home from work at night. Since the US version of the E36 low beam headlights generally suck I wind up driving with the fog lights on. They are not really designed for long distance illumination, but any additional light brought to bear on a dark country road is always helpful.

In any case, one night last week I realized that the lighting pattern was not symmetrical. It didn't take long to figure out one of the fog light bulbs had burnt out so the following morning I picked up a couple H1 halogen bulbs at the dealer (BMW part number 63-21-7-160-777) and installed them.

The procedure is simple:

  1. Push a long thin screwdriver into the upper hole in the grill adjacent to the fog light to release the fog light assembly. When successful, the inner side of the fog light will pop out as if the fog light is hinged on one side. It is not strictly necessary to unplug the vehicle's wiring from the fog light assembly. Avoid the extra work if possible.
  2. Grasp the reflector assembly in one hand while you use the other to twist the black cylindrical wiring connector counter clockwise until it unlocks (only an eighth of a turn is necessary). Then carefully separate the two components being careful not to stress the short wires.
  3. Grab the insulated terminal that provides power to the bulb and pull it off the bulb. Be careful to grab the actual spade connector and not just its protective rubber boot.
  4. Squeeze the two free ends of the bulb retainer clip together, pushing down as required to free them, then pull the arms up and allow the retainer clip to fold back and out of the way. This will release the bulb.
  5. Pull the old bulb out of the reflector assembly and replace it with a new bulb. Do NOT touch the glass of the new bulb (open the box carefully to figure out what end you're grabbing first) or it will fail prematurely.
  6. Replace the retaining clip and reattach the reflector to the wiring cap, being careful to insure that the orange sealing ring is seated properly in the cap before mating the two components and twisting the cap clockwise to lock it.
  7. Install the fog light assembly by seating the outer portion of the assembly with the vehicle first, and then press the inner portion of the glass to lock the assembly in place.
  8. Just to make sure the installation is secure, alternately push and attempt to pull the assembly out of the bumper. If it doesn't pop free the fog light is installed correctly.
  9. Test the lights. There is no need to start the vehicle to test the fog lights, but remember that the headlight switch must be turned on and the high beams disabled in order for the fog lights to work. Keep testing of lighting to a minimum with the engine off to avoid undue drain on the battery.

The bulb that failed was provided as part of the new ZKW OEM fog light assemblies I installed back in 2007. Even though only one bulb had failed I replaced the pair because I tend to follow the "rule of bulbs", which is to say that in any combination of bulbs that shares the same duty cycle, where one has failed the remainder are sure to follow shortly.

Instrument Cluster Replacement Research

After some searching online and in the TIS, I discovered that the procedure to replace the instrument cluster in the E36 is pretty easy, and should not involve any coding at the dealer, but it does have a catch.

As it turns out the vehicle's mileage is stored, among other places, in the coding plug on the back of the cluster and inside the cluster itself. If the mileage stored inside the cluster does not match that in the coding plug the mileage shown will be whatever was previously stored inside the cluster and the tamper dot will illuminate to indicate the discrepancy.

The BMW TIS documents a procedure to synchronize the mileage stored inside the cluster with the mileage in the coding plug and remove the tamper dot. The catch, of course, is that this procedure only works as intended if the mileage stored in the replacement cluster is lower than that stored in the coding plug.

My current understanding is that new clusters ordered from BMW are set to 0 miles and this procedure will set the value to the current vehicle mileage without any extra coding. If true, that means I can replace the cluster myself and save at least $250 in labor and coding charges.

Mileage: 200700, Parts: $16

Sunday, December 12, 2010

HVAC Controller Gremlins Return

Way back in 2003 I replaced the HVAC controller after it exhibited progressively more frequent symptoms and then failed entirely. At the time I had the dealer diagnose the problem and the solution was predictable: I spent $325 on a new controller and $80 in labor installing and coding it.

Yesterday morning I decided to do some errands so I hopped into the car and turned the key. At that instant I remembered I'd forgotten something in the house so I went back in to get it. Not a minute later I walked back out to the car and stopped in my tracks when I heard the aux fan spin up. Knowing full well that I'd just started the car and the temperature was in the "balmy" 40's I knew engine temperature alone could not explain why the fan was running.

I got in the car and quickly realized that the HVAC controller display backlighting was not functioning. I could barely make out the blower fan speed and tried to adjust it. Nothing happened. I then tried some of the other buttons and realized that those didn't work either. Since I write software for a living and am all too familiar with the three finger salute I turned the car off, waited a few moments, and then restarted it. Not surprisingly, the controller returned to life.

In any case, I'd seen this movie before. If left alone, the problem would likely worsen over the next few weeks and the controller would eventually stop working entirely. That's an inconvenience in warm weather but a serious problem in winter so I let my fingers do some Googling.

A quick check of my parts supplier revealed that the controllers are now $440 and have a $200 core charge. I know the core charge did not exist in 2003 because the dealer gave me the old unit back and I (foolishly) threw it out, thinking at the time that the unit was unrepairable and I would never be in a position to use it in again anyway. After all, who would have guessed I'd keep this thing thirteen years?

Fortunately, this time around I have an arsenal of knowledge available to me. As it turns out the problem is caused by a failing (or failed) capacitor used in the controller's power supply filtering circuitry. There is risk in attempting the repair of course, but as I see it the worst that will happen is I'll have to spring for a new controller and the related coding charges. If I succeed, however, I'll wind up saving at least $500. That's enough of an incentive to leverage my knowledge of electronics as well as my soldering equipment and technique.

The replacement part is on its way from DigiKey and I hope to complete the repair next weekend. Naturally, I plan to thoroughly document the process for the benefit of all.

Mileage: 201100, Parts: $10

Saturday, December 18, 2010

HVAC Controller Fixed

When we last saw our hero, he was facing a grave threat -- freezing his nads off driving down the highway at 80MPH without any heat because of a faulty HVAC controller. We now continue with the story...

The first indication of a problem with the HVAC controller appeared last weekend so I ordered a new capacitor from my electronics supplier in an attempt to do a component level repair on the unit as opposed to throwing the better part of $500 at BMW for a new unit. I knew I could expect intermittent operation of the climate control system and thus intermittent heat until it was fixed, but little did I realize how bad it would get as quickly as it did.

By the drive home on Monday the controller went from working perhaps 95% of the time to working little more than 40% of the time. Whenever the controller would stop working, the "Auto" button LED would continue to be illuminated and I could faintly make out the segments of the fan speed indication on the display, but no control on the unit worked, the HVAC blower motor did not run, and the servo motors that automatically control the inner and outer doors remained silent. No degree of menacing looks or threats of physical violence with a clenched fist helped matters. Even a few well-placed bitch slaps on the nearby dashboard structure did not convince the unit to behave. It turned on and off with no apparent rhyme or reason.

(Image: Closeup of capacitor changed to fix hvac controller) While dealing with this headache I discovered a couple things. First of all, once the car is car is warmed up, even if the HVAC blower is not operational some heat does flow through the vents due to ram air pressure, but trust me -- it's not much at all. Second, I found I could take advantage of the unit's non-volatile memory that stores the last temperature and fan speed settings. I adjusted the temperature on both sides to 80 degrees and set the fan speed to about 3/4 of maximum so that when the controller was operating it would generate enough heat to warm the interior sufficiently to compensate for the periods in which it did not work. This had the unfortunate effect of blowing lots of cold air shortly after start up but that was a small price to pay for warmth throughout the drive.

While this little "trick" made the car drivable, by the drive home Tuesday I had had enough.The weather forecast was for cold but sunny weather the remainder of the week so I decided to bring the E46 out of its lair. I hadn't driven the car much since the rear suspension overhaul so knew this would be good for the car as well as good for me. Of course, nothing is ever easy. While browsing my favorite weather site during lunch on Thursday I realized to my horror that the forecast had changed and some light but accumulating snow was predicted for later that afternoon...just in time for the commute home.

As I learned many years ago when I foolishly tried to run summer (not all-season) tires on the E36 in winter, a half in inch of snow might as well be four feet: summer tires make the car downright dangerous to drive in those conditions. I wasn't about to lose my pride and joy just to keep my employer happy so I ditched work a couple hours early to grab the E36. It didn't take much to rationalize the move: better cold than spun out in a ditch, right? And good thing too...I had just managed to put the E46 to bed and close the garage door when I saw the first snowflakes appear.

By the time I got back to my neighborhood 15 minutes later we had about 3/4" of snow on the ground and the ABS was getting a workout. I had to stop at the food store on the way so I took the opportunity to grin a bit, turn off ASC, watch out for the Federales (and, for that matter, the light poles), and play around with the effects of reduced friction in the largely empty parking lot. Mercifully, the HVAC controller decided to play nice and I had heat nearly the entire trip home. What can I say? The car doesn't always love me, but I think it respects me...and I can live with that.

Fast forward to today. The parts came in, I pulled the climate control unit, drove home with it in the E46 and proceeded to swap the defective capacitor with a new tantalum part. I ran into a small snag when I realized I'd forgotten my micro screwdriver set back at the garage, but since I knew full well it didn't have the micro (T7) torx driver best suited for this job I just ran over to Eppy's and picked up a nice 41 piece precision bit set by Sunex Tools for a mere $28. While there, incidentally, I learned that Ideal tools bought SK Tools out of bankruptcy. The CEO of the company told Eppy's management that they expect to be shipping again in March and that they were planning to keep the manufacturing facilities in the US. Hearing that I confirmed my commitment to SK Tools, and good thing too....I have a lot of them.

Back at the workbench I took the opportunity to do a little preventative maintenance and replaced the HVAC temperature sensor fan. While not exactly cheap at $125 I felt it was best to do it while I had the unit out of the car. Interestingly, I discovered that the fan lacks a tachometer output, so I know the HVAC controller hardware or firmware is not monitoring the fan's speed. This in combination with its near silent operation would make it damn near impossible to detect a failure. And since stationary DC fans present a load equivalent to a short, I felt it better to replace the fan now rather than risk possible future damage to the controller I was working so hard to preserve.

On the way back over to the garage with the newly repaired controller I found myself a bit on edge because I could not bench test the unit and so I could not be 100% sure the repair was completed successfully until I reinstalled it in the vehicle. Once I arrived at the garage it took me less than two minutes to pop the OBC and HVAC controller back into the stack, reconnect the battery, and turn the key -- to find the controller working as expected. The acid test, of course, was the 20 minute drive home from the garage...the controller never skipped a beat. My feet were nice and toasty, and I took time to bask in the warmth of the knowledge that I'd just managed to save myself $470 in parts and $130 in labor, or $600 total in little more than two hours of work. I'll say it just in case it isn't obvious: that is one hell of a DIY dividend.

Naturally, I took a bunch of pictures of the process and observed at least one thing that wasn't covered in the DIY I followed. Therefore I hope to publish a DIY of my own as soon as possible.

Mileage: 201320, Tools: $28, Parts: $125, Parts Saved: $440, Labor Saved: $130