Cadillac Tech Tips - How to fix it Discussion, INFO : The DIC - for inquiring minds in Item Specific Cadillac Discussion; I have recently had some difficulties with my DIC and thought I should post what I learned...
1989 Seville, ...
Since I bought it ($500) I noticed that the DIC seemed to be 'temp sensitive', and would black out the entire display area (climate ctrl AND 'text') somewhat randomly when the temp was about 75 or so. It usually came back when the interior of the car exceeded or fell below that. Until recently I had ignored it, somewhat grudgingly, as I didn't want to pay to replace it...
A couple of days ago when I started the car (after having driven it recently), it came on and immediately began to FADE out, as if the panel dimming had been adjusted to nothing. It also lost all the button illumination (which was working ONLY on the right half previously). This was NOT a typical behavior and I focused on any other abnormalities.
They came quickly.
Soon the speedo assembly also began to fade, slowly, and over the course of 10 minutes, came close to approaching complete black. At this time I also noticed the dreaded 'some integrated circuit is burning up' smell.
Thinking that the DIC was about to kill the central power supply, I disconnected it and the speedo immediately returned to full brightness. Of course, the AC, with loss of its control system, 'did what it wanted to'.
Meaning that it kicked on the compressor and defaulted to 'defrost'.
Knowing that this condition could not be tolerated, I removed the DIC for inspection and began disassembly. Immediately after removing its back plate, I noticed two transistors on a small raised board (which also sported an obvious 'coil') that looked as if they had spent the week in a toaster oven. This board was obviously some sort of voltage control unit.
Everything else appeared okay and, since I did not want to leave the unit out of the vehicle and knowing that it was DOA anyway, I removed the two charred pieces (by snipping leads) and returned the unit to the vehicle to determine if the DIC was still controlling what it should.
Altho the DIC display and the button bulbs do not light, it DOES continue to operate those items that it is expected to, and I can continue to use the vehicle until I can get to the trusty salvage-yard in hopes of finding one to replace it.
I have also confirmed that the dimming control continues to function properly on the speedometer, so that, fortunately, has not been damaged, and it seems that the central power supply is also well.
Once I find a new unit to substitute in, I intend to attempt replacement of these dead transistors and, with luck, be able to keep it as a spare....
Hope this at least makes for some interesting reading!
Automobile(s): did this once... 86 Deville, 86 300E, 78 R100rs
Palm Spgs CA
Re: INFO : The DIC - for inquiring minds
Originally Posted by 92EldoTC
Wow, that is interesting. Sounds kind of complicated removing the DIC without messing the display up.
The connector for the DIC (on the 89) is a single multi-pin connector. The only thing that happens SEEMS to be that the communication (a serial line, supposedly) to the AC programmer 'drops' and it does funky things......
Since I don't know the details of the 'power convertor' on the back of the DIC I cannot elaborate on the symptoms I experienced, other than.....
1) The transistor failure/shorting to ground SEEMED to result in the reduction of the 16v 'drive' voltage to the displays close enuf to zero to cause the reduction in the display I experienced....
2) The fact that complete disconnection of the DIC returned the speedo to normal operation TENDS to confirm that the 'fault' is limited to the DIC power/conversion/modulation circuits....
3) The confirmation that the 'fault' exists in the DIC does NOT confirm that the failure of the two transistors previously mentioned was SOLELY to blame for the resulting failure..... there MAY be other DIC-internal factors that contribured to the failure of the transistors... meaning that, if/when I replace these transistors, they MAY fail again...
Other than the above, I think that, with the knowledge of the transistor numbers, I could/can/wanta return the DIC to 'standby' status once I get one that works 'right'....