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89 Eldorado
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I have been asked to troubleshoot a dead digital display on this 89 Cad Eldorado. No segments on any portion are
illuminated. I’ve checked all voltages on the two cluster connectors and they are per the shop manual. The owner states
this cluster was checked and tested Good. The left and right control panels as well as the radio display vary in intensity
with the Interior Light control. The Driver Information panel with the incandescent bulbs appears to be very bright.
Here are some questions that may direct me to further troubleshooting.
First, is there a code to enable the display as later model cars have or some combination of button pushes to enable the
display?
Second, is there a voltage measurement I can make on the PC boards to verify the fluorescent displays are powered? I do know how to read schematics. I suspect there is a high voltage inverter to power the display.
I have replaced the Central Power Supply only because the owner purchased one as a suggestion. It did not change the
digital display. I understand the data for the display is through a serial link but could that cause all function to not work.
Even the directional light displays do not illuminate.
Any help would be greatly appreciated.
Best regards,
Dan Kahn

I have been asked to troubleshoot a dead digital display on this 89 Cad Eldorado. No segments on any portion are
illuminated. I’ve checked all voltages on the two cluster connectors and they are per the shop manual. The owner states
this cluster was checked and tested Good. The left and right control panels as well as the radio display vary in intensity
with the Interior Light control. The Driver Information panel with the incandescent bulbs appears to be very bright.
Here are some questions that may direct me to further troubleshooting.
First, is there a code to enable the display as later model cars have or some combination of button pushes to enable the
display?
Second, is there a voltage measurement I can make on the PC boards to verify the fluorescent displays are powered? I do know how to read schematics. I suspect there is a high voltage inverter to power the display.
I have replaced the Central Power Supply only because the owner purchased one as a suggestion. It did not change the
digital display. I understand the data for the display is through a serial link but could that cause all function to not work.
Even the directional light displays do not illuminate.
Any help would be greatly appreciated.
Best regards,
Dan Kahn
 

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Registered
1970 Eldorado.
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4,023 Posts

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Registered
89 Eldorado
Joined
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4 Posts
Discussion Starter #5
Well after much troubleshooting and a lot of reading of schematics I have found the problem. The VF Power, which stands for Vacuum Fluorescent, 55 volts was not present on connector C201. Tracing the circuit flow, this voltage goes to the VF displays in the Climate Control Driver Information Module. when I removed the module the Instrument cluster came to life. Upon opening the CCDIC there was a transistor surrounded by blackened circuit board. I am in the process of trying to purchase a new CCDIC and also to trace the circuit on the defective module. My concern
is if there is something external to the CCDIC that could have caused the failure and replacement would be damaged due to this external
malfunction.
Looking at the functions of the CCDIC, the data is decoded from a serial link from the BCM. An on circuit microprocessor then displays the
information on the VF display. Other than a shorted VF, the only other possibility is a component failure in the 55 volt circuit. When I get the
module back, (I returned it to the owner to see if he could get it repaired) I'll trace the circuit to find the bad component. I may have to use some old transistors I have in my stock to replace the defective device.
I will see how it goes upon investigation.
 

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2001 eldorado,2008 DTS,2005 XLR, '96 eldo,'95 eldo,' 89 eldo,'78 eldo,'11CTS-V
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1,719 Posts
I have spare IPC's and CCDIC's if interested, but we're leaving on holiday today, and won't be back till june 28.
 
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