1989 IPC connections

[89RedDarkGrey]

To anyone who has removed an '89 dashboard- besides the 2 obvious IPC clipped-to-dash sockets- is there a "plug" or splice connection that runs in the harness that's attached to a section of black plastic, just below the glove box, that feeds the cluster?

 

Back when I was hunting for the {found} ECM harness short that was causing an E042 and stalling, I was forcefully tapping up on the BOTTOM EDGE of the dash, under glove box- and the IPC went blank, and is still blank. I haven't checked all fuses yet. CRT functions flawlessly (recently rebuilt), ECM replaced long before this happened. BCM appears to function normally, all DATA, INPUTS, OUTPUTS, and OVERRIDES on both appear normal. No codes from ECM, BCM, CRT, ICP.

 

THANK YOU FOR ANY HELP.

 

[KDirk]

I don't think there is any intermediate connection between the main dash bulkhead connector  (the big black rectangular job) and the IPC connectors, but I have a full dash harness I'll look at tonight and post back my findings.

[89RedDarkGrey]

My next tests will be with a DVM check the 2 IPC in-dash connectors (per FSM) for GND, +12V and +5V with KOEO.

 

If those are correct- a United Radio IPC rebuild is in my future. They're 45 miles from my house.

 

I just don't understand- how a moderate hit on the opposite side of dash could totally kill the IPC. If the wiring is anything like the ECM (hard, brittle, shorted) that would explain it, though.

[KDirk]

Ok, have looked over a dash harness I had in my inventory and I do not find any intermediate connector in line with either of the two harness sections  that terminate at the IPC (the two red/black shell connectors). There are a number of plastic mounting flags taped into the harness along its length for screwing to hold points on the back side of the Dash panel,  but there is no other connector  visible. Most of it is in loom and taped over, but even then a pull-apart termination would be visible as a bulge.

 

Check for power and grounds at the IPC  connectors. If all voltages and ground are present but the entire cluster is blacked out then the cluster, by process of elimination,  is smoked. I'd be a bit surprised that it would go like that though. The 88/89 cluster tends to either loose the digital displays (via failure of the internal VFD high voltage supply)  or  the incandescent telltales stop working, but it is unusual for both symptoms to occur concurrently. A full failure of all IPC functions is more likely a fuse or wiring fault killing all power to the cluster.

 

 

[89RedDarkGrey]

8 hours ago, KDirk said:

The 88/89 cluster tends to either loose the digital displays (via failure of the internal VFD high voltage supply)  or  the incandescent telltales stop working, but it is unusual for both symptoms to occur concurrently

 

CRAP. I forgot to mention- that all Telltales and switchpod backlights DO WORK with key-on bulb check and in normal operation, and the TEST button also runs a bulb check of all incandescent. Only the VFD is blank.

[KDirk]

Then you, sir, have a cluster rebuild in  your future. Please post if United repairs the 88/89 cluster. I know they do 90/91 but not sure if they will do the early one. If they do, I'll probably send them one or two I have sitting that I have not been able to resurrect.

[89RedDarkGrey]

Thank you kindly

 

Just for S&G is there a fuse, breaker, relay- or fusible link that would cause the VFD part to die like that?

 

Again- I just don't understand- how a moderate hit on the opposite side of dash could totally kill the IPC (VFD part).

[KDirk]

 

No fuse that would only kill the digital portions of the display.  The high voltage for the VFDs' is derived from the 12VDC common feed to the cluster, as the high voltage supply is internal to the IPC. The same 12V is used to power the various telltale bulbs (which are 12V #160 wedge base lamps IIRC) when they are called for  (these are individually controlled by transistor switching  under logic control within the IPC).