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1995 164 LCD Disassembly/Repair Procedure

6523 Views 15 Replies 6 Participants Last post by  goats
I have had my 1995 164Q for about 3 years now and I feel it is time to repair the LCD Climate display. The display is totally blank. I removed the climate control assembly from the car and tried to open it, but was not able to fully open the assembly. Does anyone have some disassembly instructions/tips on how to open up the LCD Climate Control assembly? Thanks.
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Goats in San Diego(?) rebuilds them. pm him for a price. I think he also posted at one time how to fix them. Do a search, or google it:)
I was lucky enough to buy my LS with the Goats repair already done. I tell you no lie when I say I feel lucky to have a working HVAC and display every time I drive her. Do the repair as it will make you love your 164 more!
Yup, mine, repaired by Goats, works just fine. Thanks.
yeah I haven't repaired any for some time -- I am out of the polyimide flex cables I had made, and my access to bonder is very very spotty (ie not reliable enough to promise a turn around time). To recap what the issue is

1. The orig climate module was subbed out to Bosch who then subbed the circuit board and display to a French company (early 90's)
2. French company used a mylar flexible connector that joins the LCD glass to the driver board and used heat seal technology to join the mylar 150 conductor cable to the lcd glass and gold plated lands on the driver PCB
3. Bad choice of materials. Mylar is like scotch tape and cars interior gets >120F in the summer time here in USA in many locations, and <-20F in winter as well
4. Under the heat, the mylar gets soft and the heat seal degrades. Under the cold, the coeff of expansion between the heat seal/mylar/glass/pcb is enough to interrupt the circuit
5. Many of the units also show abrasion from the clamshell connector onto the mylar connector thus physically interrupting the silver conductive trace.

So I designed and tooled a polyimide connector and developed ACF bonding using both 3M and Sony ACF rather than heat seal adhesive. Very robust very reliable. I got access to a bonding lab first in Arizona and then here (twice). Unfortunately ACF bonding is yesterdays technology so not many places have adequate bonding capital tooling any more. I ran out of all my connectors and didn't place another order

That being said, on Ebay there is a guy selling what looks like the original mylar connector for $18. I don't know if anyone here has tried it but for 18 bucks its worth a shot! Could prob get ACF and try bonding by hand and see what you end up with ... cheap enough experiment I guess. ACF is hard to work with though. Its finicky and cures under pressure and temperature with pretty narrow ranges. There is now a 3M tape that one might try to bond the connector with ....
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I'd like to get to the point where I can repair the damaged parts, but I was not able to open up the assembly.i was able to remove the screws, but was not able to separate the pieces much further. Is there a hidden screw or locking tab that I am missing?
Remove the 4 screws from the back. On the sides there are detents ( one on each side) that have to be relieved to open the assembly. Depends on the revision of the module it might be a small wedge fully enclosed in a tiny relief or open on one side. Just gently pry it out. Get the 2 case halves slightly separated and turn it over face up with LCD glass at top. Pry out gently the ribbon cable connector board on lower left and now the clamshell will open " up and down".
And do not forget that the electronics board is also held on with some small silver screws. In my case, the panel had a stain on the inside, like a liquid stain but the display worked. It seems that some of the glue holding on some foam spacers basically melted down and that was the stain. cleaned it up and all is fine. Delicate stuff so careful not to pull at the connectors.
The yellow glue that "melted " was the adhesive used to secure the diffuser to the back of the LCD glass. I would estimate about 70% of the modules I have repaired had similar migration of the adhesive. Beeton is fortunate that his Mylar connector is still good with the heat seal bond. Not too many original cables working any longer from what I've seen.

Also once the clamshell is open there is no need to remove any other screws. Both the clamshell connector (lower left corner) and the LCD driver board are held in by nylon standoffs. Gently pry the connector up over the standoffs, and for driver board use a hemostat to squeeze the top of the connector and gently pry (gently) the board over each standoff. Sometimes the standoff will come free at the base - no big deal, these are all press fit and won't be damaged
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Got Climate Control Display Apart

Happy New Year, everyone! Following goats instructions on how to open the display, I was able to find a little time to take apart my old climate control display. I have attached some pics of the assembly. The mylar flex cable to the LCD display looks to be in good shape to me. Not sure why the display does not show any working segments. Goats: Would love to hear your comments. Thanks


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did you check the 3 green backlight bulbs? If they are burned out you will see nothing

Otherwise your mylar cable , like the 100+ Ive replaced, is delaminated on both the board and glass side. There is no way for you to determine this fault though without some specialized test equipment. Its not visible. What happens is the 'heat seal' bond that Bosch used to connect the conductive traces on the mylar cable to the a)gold plated traces on the driver board, and b) the iridium traces on the glass breaks down. the actual mechanic/electric bond is compromised. Its possible, but highly unlikely, that your issue may be a driver board issue, but I;ve not seen this fault except once when someone spilled pepsi inside the module. Mylar is horrible for his application as is heat seal adhesive. Proper way is polyimide and ACF adhesive. The link below is very old and out of date -- in fact, factually incorrect in some places but will give you a decent overview.

Connecting Flat Panels to Circuit Boards | Thermal Press | 925-454-9800

The observation that you get ZERO segments is unusual, but NOT unseen previously. Typically its 'klingon' display. Check those 3 bulbs and make sure they are lit.

PS your photo on top in post 10 seems to show visible delamination on the glass side. The very middle 1/5 seems still bonded while the rest looks delamed to me. might be a photo effect tho

Also -- beeton is fortunate where he lives, super high temps probably not experienced. Here in So Cal in the summer the inside of a 164 in the sun will exceed 130F no problem and that's why mylar is bad design choice
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True but our summers can be humid and temperatures reach upwards of 34c (about 97f) so the insides of my little red microwave gets pretty hot.
My left display is dimmer than my right display so I may put this on my "to do" list over the winter months. i want to pull out the stereo and add a 3/4 inch spacer to allow it to sit further out... making the reach to the controls a bit more comfortable so might as well do it all at once.
Higher resolution pics

Thanks for the comments. I will check the bulbs. Here are some higher resoluion pictures of the mylar cable assembly.


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Check bulbs

What is the best way to check the bulbs? After looking at the clamshell asembly I am planning to re-assemble the unit without the LCD ribbon cable assembly and install it into my car and see if the lights turn on when I set the ignition to ON.
Bulbs do not light up

I re-installed my partially assembled climate control display (no LCD display - so I can see the 3 green bulbs). When I turn the ignition from OFF to ON I do not see any difference. The 3 green bulbs look like they are not lighting up. Where can I get replacement bulbs?


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Audi dealer. 2wAtt 12 volt green base bulb and u need to remove the little green condom from your bad bulbs carefully and put in the new bulbs. Search this forum for LCD BACKLIGHT
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