Results 1 to 10 of 10

Thread: Auto-dimming Mirror(s) Not Working

  1. #1
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17

    Auto-dimming Mirror(s) Not Working

    89 SC. Came with an automatic dimming mirror and back when it ran in the 2000s I remember distinctively with a car behind us the glass would tilt, I'd hear a gear whir noise, and the mirror would dim. After getting it restored after sitting for 8 years it doesn't dim anymore, so I ordered a salvaged one off of Ebay... and that one doesn't dim either. Both tested at night, and the lights on the controls work. Distance light clicks on when someone's behind me or shined at with a flashlight, and even the auto-headlights work. Haven't figured out the auto-dimmers either, but I only got to test them once with no luck. Highbeams won't come on at all.

    I took the Ebay one apart and tested connections for any breaks in the circuit (I'm no electrical engineer though. It's only my fourth time using a multi-meter) as well as tested how freely the gears spun. Everything seemed to be in check, and I even took photos while I had it apart. Still, nothing. Also how on earth does it tilt? I saw zero parts that allowed for tilt-action. It was just a sheet of glass resting on a (rather static) circuit board with no hard connections or adhesives or anything.

    The setting dad always left the dial on it was FAR because "I prefer the mirror to dim sooner than later" and I haven't messed with it. Truth be told I don't know how on earth this is supposed to work internally. Maybe it's operator error? I really don't know.

    Here's the Ebay one. I'm having a heck of a time trying to get the one off that's still in the car, although I saw a hex-nut was hiding under the high beam sensor so maybe that needs to come undone first?
    Name:  MirrorSC.png
Views: 105
Size:  672.5 KB

  2. #2
    Join Date
    Jul 2018
    Location
    Northern Kentucky
    Posts
    19
    My 89 SC has this option also.
    These pics are out of my 1989 owners guide.
    Explains how it should operate.

    Last edited by CR125Honda; 11-01-2018 at 02:56 PM.

  3. #3
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,785
    Quote Originally Posted by FurryWrecker911 View Post
    Also how on earth does it tilt?
    I don't think it physically tilts. I think the mirror surface is bent/warped/distended, instead, causing the coating(s) to alter the amount of light that is reflected back to the driver.

  4. #4
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17

    Performed a second autopsy

    Today I messed with both mirrors hooked up to the car and spun the dials of each to no avail. I then took apart the mirror from the car to tear it down. First thing to note is I did find a contact point. It's this screw that has a cap on top of it. It's the ONLY thing from the board that the mirror comes in contact with, and it's rusted as hell on the mirror that was in the car. The replacement mirror's screw looks brand new, yet it didn't work as intended either.

    Again, did a haphazard multi-meter test, and most of everything checked out. It's making me wonder if the mirror isn't getting sufficient power, like there is a ground issue further up the line. Is there a cheap way I can bench-test these, like hooking a battery up to them and seeing how the operate standalone?

    And yeah, I can conclude it doesn't actually tilt. I just remember it doing this "flip" style thing so vividly when I was a kid, but I suppose that's a child's memory for ya.

    OH, and I'm not sure if this has anything to do with it, but the auto-lights mode works when it's dark, but the auto-high-beams do not. Since they're part of the same module it's making me wonder if they're in the same circuit altogether, and it's receiving a false-positive that the car is in reverse. Really, a bench-test would solidify this.

    Here's some photos of the board from the car. Maybe something will stand out as being out of place.
    Name:  1989_ThunberbirdSuperCoupe_MirrorBoard.jpg
Views: 90
Size:  2.86 MB
    Last edited by FurryWrecker911; 11-01-2018 at 08:47 PM. Reason: Specified which board is in the photos

  5. #5
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17

    Might be on to something...

    Did a multi-meter test on the harness. Kept ground on the ground socket. Getting 11.5V coming off the positive socket and 30mV coming off the Reverse socket? Not sure if that's supposed to be happening or not.

    Considering getting some 8-inch 20-something gauge wire and a spot of electrical tape and running just the positive and negative to the mirror and seeing if it'll work right as a test. I don't want to outright snip the reverse line. If it works then I'll work my way down the circuit sometime. If it doesn't work still then dang, I have two bad mirrors.

  6. #6
    Join Date
    Jan 2010
    Location
    Bossier City, LA
    Posts
    2,243
    Reverse goes to 12V to signal that you're in reverse; that voltage is probably leakage around.

    You may want to consider an electrochromic auto-dimming mirror and replace that one; it's what I've got in Ruby Jean.

    Since she didn't come with auto-dim, but had the wiring up in the headliner.

    Scout Ebay; I picked up a pair of NOS Toyota units for $20 each with the compass ... but you can buy new for under $200, so you have to figure how much time you want to spend fixing the original (and that may depend on if you're keeping "highly original" or are like me, "spoiled with not having to flip the mirror"

    Here's a match to the one I bought for Ruby (and the second one to add to my Dakota; LOVE that mirror in the Dakota!) https://www.amazon.com/Gentex-GENK5A.../dp/B002Z61QAU

    *dry* Yes, it's a bit more when the seller knows what they have and what it's actually worth.

    RwP

  7. #7
    Join Date
    Jul 2018
    Location
    Florida
    Posts
    17
    "Reverse goes to 12V to signal that you're in reverse; that voltage is probably leakage around."

    Alright, thanks for informing me of that.
    I saw TBSCShop had two originals reportedly in working condition for sale on their site, so I might give them a gander if I can't figure out how to fix these by the end of next week. It's just so bizarre that they don't work. The transformer has continuity and I can get continuity out of the arms as well when I close the circuit, as well as several of the paths from solder point to solder point. The photocells obviously work as well as the distance/power switches. Just something is inhibiting the transformer from turning the gears on both mirrors.

    Right now my fear is if I do drop the money on yet another mirror the dim function still won't work, but as of now it's looking like I have two lemon mirrors. Oh well, at least I can manually tilt them in the meantime! lol!

    I'll update again come the next set troubleshooting I do here. If my janky positive/ground wire test doesn't work I'll focus on following the path from the photocells and distance light to the transformer and try to find any breaks in the path or failed resistors. Getting a lot of practice the the meter, that's for sure. Might buy a solder iron at this rate. :P

  8. #8
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    6,785
    Prime suspects on older auto electronics are cold solder joints and blown capacitors. I zoomed your photos and neither jumped out, however.

    My '90 EVTM, BTW, says 'solid state' about the mirror itself. Otherwise it shows 3 BK wires: GND, pwr dist, reverse circuit. Not much help there.

    Summary of:
    'How The Circuit Works'

    W/the ign. switch in run, power flows thru the run fuse and the 298 (P/O) wire to the mirror. A Photocell Amplifier in the mirror activates the electronics circuit when headlights from the rear are sensed.

    The backup switch closes in reverse...when closed, power flows thru the Turn fuse and 298 (P/O) wire, the switch, and the 140 (BK/PK) wire to the mirror. This voltage deactivates the electronic circuit in the mirror to prevent switching to the night position.
    Last edited by KMT; 11-03-2018 at 10:07 PM.

  9. #9
    Join Date
    Jan 2010
    Location
    Bossier City, LA
    Posts
    2,243
    I'd be checking the transistors and considering replacing them and the LM2901 just because.

    The actual switching action is started by the LM2901; I think the transistors are there to actually drive the motor. I haven't traced such a design out, but that's what I would do.

    Also, depending on what they're using for a photoreceptor, THAT may be failed; either the dark set or the lights in.

    Last but not least, check the "Near/Far" potentiometer; IT may have opened with age.

    Of course, check the motors; but IIRC, you've done that.

    (I STILL say you ought to just buy a new electrochromic mirror, but not my car, not my money.)

    RwP

  10. #10
    Join Date
    Jul 2004
    Location
    Salt Lake City, Utah
    Posts
    1,520
    Back in 1994 I replaced the electric motor in my 1989 with the IHC Carnival 12vdc #5115 motor. It is still available online or you could try a hobby store for something similar. The only issue with the motor was that it would tilt the mirror so fast that it would overshoot and tilt back and forth continuously. I added a resistor in series with the motor and it worked perfectly for many years until I sold the car.

    I repaired and verified operation of the mirror after removing it from the car, and used a 12v power supply to power it and a flashlight to trigger it.
    At the very least, I would check the motor by desoldering the motor wires from the PCB and use a 9v battery to directly power the motor. If the motor does not work, you could try to open it up and clean the carbon brushes, but you will probably destroy it in the process.

Similar Threads

  1. Auto dimming mirror wiring??
    By 91BlackBird in forum Technical Forum
    Replies: 20
    Last Post: 07-04-2007, 07:27 AM
  2. Auto Dim Mirror
    By Thunderbird84 in forum Parts for Sale
    Replies: 1
    Last Post: 08-01-2005, 07:05 AM
  3. Auto Dim Mirror Help
    By Scour_king in forum Technical Forum
    Replies: 5
    Last Post: 07-17-2005, 10:58 PM
  4. Auto-dim mirror installation, for those who asked
    By metalman in forum Technical Forum
    Replies: 6
    Last Post: 07-19-2004, 07:43 AM
  5. Auto dimming mirror
    By MTTod in forum Technical Forum
    Replies: 0
    Last Post: 04-19-2003, 11:37 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •