I know this has been discused some times before, but i am interested, if somebody found the reason why some of the early (and late ?) A/C displays start to dim, and fade away all the way after a while.
Mine starts to make this since a few days. Once in a while i cannot read anything on the display. I read before that there might be only a little electronic part which has to get replaced. My brother is an electronic specialist, and if i can tell him whats broken, he might just replace the part.

Thanks for any info about this.

Jochen

 

Jochen,
Interesantes thema..Ich hab daselbe problem aber keine loesung...

 

Hi,
eine Lösung gibts schon. Allerdings heist die die gesammte Steuereinheit für die A/C zu ersetzen. Kostet wohl (Material only) so um die 400 US$.
Hoffe ich bekomme das noch anders hin.

Grüße

jochen

 

Huh? Help me out, some of us English speaking *****' have this problem too.:D

 

Sorry,
we still havent find a "DIY" fix, except exchanging the whole unit, which might cost 400US$ plus labor. However, i think you can get the part more cheap from GMpartsdirect or Ken Fichtner. This will be the way to go if i cannot get it fixed.

Jochen

 

I bought one used off the "for sale" section for $75 and installed it myself. It is very easy to install and you can usually pick one up for about $75 - $100 used. I have seen Gene (Karshop) have them from time to time and he has ALWAYS been very fair with everyone that I have known. I thought about trying to work on mine but couldn't get anyone to give me a wiring schematic. Best of luck to you.

Jeff

 

;)

 

There's a broken one being shipped to me right now. If I figure something out, I'll post it.

I'm trying to figure out how to jig one up with power and signal outside of a car before it gets here.

 

Sounds good, i will keep focused on that. Do you have the layout of the electr. circuit ? If so, i would be interested in getting a copy !

Thanks,
Jochen

 

Gene or eBay...you'll find one near $100...

 

Electrical diagrams are in the service manuals. $109 for a complete set on paper from Fichtner. Best mod money you'll ever spend.

 

I got the broken control unit last night. Opened it up easy enough. (3/16" bolts, metric/smetric!!).

Inside are two circuit boards. The rear board has one large and one 20 pin chip, through-hole DIPS. This board appears to have all the "smarts" on it. Most of the parts have Delco part numbers, which can be very difficult to cross-reference. Most of the components are through-hole types, which are very easy to replace. Many of the resistors and capacitors are surface mounted as are a few other components.

The front board has one 40-pin (roughly - didn't count) DIP underneath the VFD (vacuum fluorescent display tube). The rest is a handful of switches, LED's and plain old incandescent lamps. A handful of surface mount resistors and caps.

Next step is to figure out how to jig this thing up outside of a car to get the display to light up. Doesn't matter what it lights up, just need it to light up so I can measure the relative voltages across the VFD and figure out if it is something simple to fix or not. Typically, these things like to see a couple of volts across the filaments and anywhere from 9-24 volts from cathode to plate (lit segment) at full brightness.

In similar technology, there's usually some sort of power supply to increase the 12V to something higher to run the display. Very often, it's the step-up supply that fails.

I think I've identified that section of the unit. Just have to figure out whether it will light up in the absence of class-2 serial data telling it to light up.

Hopefully, just applying ground, 12V battery and 12V ignition and instrument panel lamp signal voltage will do it.

The rest of the pins are for motor control and feedback sensors and temperature/solar load sensor input. These are easily subbed on a test bench with fixed values if need be.

The serial data though is another deal. I'm not sure if I have means to synthesise that data off the car. If this thing has to be told to light up, then I don't know if I can test it off-car.

 

Great, looks like we might getting closer to the problem. If you really find out what causes the problem, we should get together, make some pictures and create a tech tip.

Keep me informed about it !

Jochen

 

:lurk:

 

TT

 

:lurk: :cheers: :seeya

 

Be careful. They could be using some type of charge pump. It uses a couple of caps and about 3 diodes and can produce about 50 volts. Does it have a 8 pin IC. If so probing some of the pins can ruin the display operation completly. Is the display dim or are they blank? :thumbs:

 

I have a used Dual Zone AC display for sale if anyone is interested.

 

Larry,
Keep in mind that when they go bad, there is a mechanical cause, you can tap on it and get it to go brighter or dimmer. I pulled mine apart and find all the soldering looks prefect, I believe it is INSIDE the florescent display itself!! If we could only buy that display, we could fix alot of them, mine included...
I was able to buy a used one from Gene on the Parts forum, VERY easy install. I have a '99 coupe, the new one was from a 2001 Z06 (I believe he said) and has a different part number but works fine. Not sure but it probably has slightly different code, it seems to go into my desired Manual mode much easier..

Gary

 

Would my extended warranty cover the problem?