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After a fairly exhaustive search for answers to this question in all of the normal places and coming up empty, I'm making this post for two purposes:
1) To possibly help someone else going through the same head-banging process, and
2) To hopefully get confirmation that I'm zeroing in on the solution
PROBLEM: Driver's power window work's perfectly for 26 years, and then finally "gives up" after a single AUTO roll down event. At this point, the motor can be heard spinning in either direction (up or down) when actuated by the switch, but the window stays in the down position.
FAILURE MODE: Rubber "shock absorbtion" system inside window motor separates, allowing the motor to spin, but not produce enough torque to raise the window. (Exactly as seen
SOLUTION: (sort of): Having had good luck with Autozone replacement window motors in the past, I picked up a replacement (Dorman), and in short order, I had the window zipping up and down very quickly (faster than the OEM motor). HOWEVER, the auto-down feature of the window now no longer functions. Not satisfied to leave well-enough alone, I start down the road of thinking, "this cannot be a coincidence," but I did fine ONE post in the forums here where the OP was complaining of the same problem (no AUTO function) and the conventional wisdom was to replace the driver's side switch control module (LCU01). Given that these are a dime a dozen on eBay, I figured, why not...easy/cheap process of elimination.
After receiving the replacement unit (which had a confirmed good Auto-down function), the problem persisted. Go figure.
Instead of just living with the totally unacceptable extra 0.5 seconds of leaving my finger on the switch and calling it a day, I go spend the next hour digging into the ELectrical (EL) system section of the service manual and find the On-Board Diagnosis Mode IV test within the In-Vehicle Multiplexing System (IVMS), page EL-191, because clearly I have nothing better to do...and my best interpretation of the function of this test is as follows:
1) Mode IV test automatically rolls down the driver's side window until either,
a) it reaches the bottom, OR
b) it is interrupted by the window LOCK switch or actuation of ANY of the remaining door window switches.
2) Either condition, a or b, causes the window to stop and diagnostic mode to exit
When I initiated this test, the window started to roll down, but moved only about an inch before it immediately stopped on its own. I'm not 100% sure, but this just seems to be wrong. I believe the window should have rolled all the way down on its own unless interrupted.
The KEY COMMENT in the FSM may be as follows:
*** "Power window motor (down) ON... during electrical ripple detection" ***
I'm purely guessing at this point, but it would appear that the AUTO down feature works by the control switch (LCU01) electronics board monitoring the motor's ripple current until the window hits the bottom of travel, at which point the ripple signal ceases, and the microprocessor within the door control switch sends a signal to the Body Control Module (BCM), telling it to UN-latch the down control signal to the window. Whew.
HYPOTHESIS: The running characteristic of this aftermarket motor is somehow different enough that the "ripple current" detection circuit is simply not working. In other words, when I fully depress the switch to the AUTO position, the microcontroller thinks that the window is already all the way down and does nothing.
At this point, I'm ready to pick up an OEM motor off of Ebay just to check the theory, but If this theory proves to be true, I'm going to be blown away that this has not been documented somewhere already. Maybe no one who still has one of these cars really cares about losing the auto down feature, as long as the window goes up and down...always possible. Anyway, The only other possibility at this point would be something wrong with the BCM, but I'm thinking that would be a very distant second to the motor theory.
If anyone with a functional AUTO-down driver's window has the time and the inclination to run that MODE-IV diagnostic (page EL-191), I'd be very curious!
Procedures to run test shown here.
I ordered and installed this one back in 09/18, and it has worked flawlessly to this day. It rolls down quicker than my passenger side, but may be due to a tired original unit...
OK, thanks. I sure thought it would have been plug-and-play as well for ANY motor. It's really going to be a head scratcher if it ends up just being that Dorman motor and that OTHER after market motors are working fine. Looks like I'm gonna have to try the OEM motor (or one like yours) just to be definitive. But with the luck I've been having lately, watch it be the BCM...ugh.
and calling it a day, I go spend the next hour digging into the ELectrical (EL) system section of the service manual and find the On-Board Diagnosis Mode IV test within the In-Vehicle Multiplexing System (IVMS), page EL-191, because clearly I have nothing better to do...and my best interpretation of the function of this test is as follows:
