Lee Beery

Instrument Panel is blank

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:(Just acquired my second 1990 Reatta from an auto dealer in Washington.  Before I took possession a  test drive turned up a blank (no indication of any kind) instrument panel.  They replaced the alternator and the problem went away.  Now that I own the car, with in 100 miles the dash went blank again.  I have searched the manuals and can not get a clue as what is wrong.  Has anyone run into this problem or has suggestions for a fix?

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Almost certainly a bad cluster. This is common on 90 and 91 Reattas. The alternator change "fixing" it is most likely a coincidence. The high voltage power supply within the cluster has failed  causing the digital displays to black out. The cluster needs to be repaired  or replaced with a working unit. There are a few vendors here who sell working used clusters, and there are a number of places around the country that will repair them.

 

If the displays return and then blank again, it is probably a thermal issue causing the loss of power after the circuit board has warmed up a bit in operation. Even in that case, it will still need repair of the compromised portion of the circuit board. Note that the mileage is not stored in the cluster,  so swapping it with a working one will not impact the odometer reading

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As Kevin mentioned the bad alternator did not cause the IPC to go bad but when you have low voltage the IPC will read ERROR and OO.

The '88-89 IPCs were very good and seldom went bad but for '90 and  up they were the most common part to go bad in those cars.

I do have some tested good used '90 and up IPCs available.

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Here is a reply to my own request for help.  After making several checks involving body computer and alternator/instrument cluster circuits found the circuit that protects alternator feedback voltage was blown.  #9 in left side fuse panel.  Replaced fuse and had working panel and alternator.  I was a little shaken when I was told the instrument cluster had failed. 

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Well, that's a new one. I'll have to look at the schematic to sort why that blacked out the cluster, but suspect that fuse must also supply the operating voltage in run to the IPC. Glad to hear you got away easy this time, these cluster have a reputation for failing just as you experienced.

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And this also goes to prove the value of the forum as while pretty much everything that can go wrong has been encountered and posted by one or more members along with the fix, every once in a while, something new turns up.  As the 90/91 IPCs have been so failure prone, exhibiting the same blank panel symptom, that there is an almost autonomic reflex as to the solution.  The alternator circuits in the Reatta fail so seldom (I have NEVER had such in my '89...still running the original alternator) that this particular failure mode for the IPC may  simply have never popped up previously.  Good catch!

Edited by drtidmore (see edit history)

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:(:angry:I'm not smiling now.  I still have a IPC problem as within 50 miles the instrument cluster went blank again. Found # nine fuse blown.  My friend that is the lead man on this problem said that would happen as we had not found the problem.  We are getting deeper and deeper into the FSM trying to figure out what is going on.  Without a FSM you would not have a clue what to look for.  I now believe this car was traded in for a Mercedes because of the problem.  The one thing we have not found is a schematic for the IPC. Also on the symptom table of the FSM,  elect diag  (8a-82-9) it says ((Cluster does not light up, refer tp Section 8D, loss of IPC Display chart...Dang,I can't find that!  Anyone that has been down this road before, please step in and take a swing.

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Perhaps the IPC going black is the result of the fuse blowing - not the cause of the fuse blowing.

 

Are there two #9 fuses? I don't have a '90 model to actually look at so I'm sort of flying blind. The #9 fuse (HVAC) I see doesn't seem to have anything to do with the alternator but it does power the IPC. Maybe I'm looking at the wrong #9 fuse.

 

When I look at the schematic of the circuit of the #9 fuse that powers the IPC, I think the left switch assembly is where I would look first for the cause of the fuse blowing. It carries the most current. You could disconnect the switch and drive the car for 50-100 miles and see if the fuse blows. Or you could install another switch that is know to be good and drive to see if it still blows. That would eliminate the switch as the problem with the fuse blowing. .

 

Fuse-9.jpg.1f851bab18e01b4f2c23aebe213abec7.jpg

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I have an '89 Reatta coupe and the IPC is blank.   The test shows lights and the computer screen works.   Is the IPC fried?

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