Instrument panels

[Bushwack]

I was reading the buy/sell section regarding instrument clusters discussed by Steve and Dave and decided to post my question here.

What is/are the differences between the instrument cluster of an 88/89 vs 90/91? Visually, they look the same (to me). Are the connections different? Is it a general build quality issue?

[DAVES89]

Connections are different and the 88/89 is digital while the 90/91 is analog.

The 90/91 cluster is the "weak link" in the Reatta, while many percieve the 88/89 cluster to be very tough. I have one in my Black that I pulled from a '86 Riv. that had been in the U Pick [not the one I usually go to] yard over a year. The drivers window was out, but I bought it anyway and it works great. I have had it my Black now over a week and all is good.

[Ronnie]

What is/are the differences between the instrument cluster of an 88/89 vs 90/91? Visually, they look the same (to me). Are the connections different? Is it a general build quality issue?

Bushwack, as you can see in the photos below they are completely different visually. I just happened to have a photo of each one and thought you might want to take a look at them so you could compare them.

[Bushwack]

Darn! I knew that. I had a 'memory moment'.

[KDirk]

Having been in the process of developing a rebuild process for 90/91 clusters for a while now (have successfully rebuilt a few) I have decided that the weak link in the design stems from two points:

1) The 90/91 cluster is heavily reliant on surface mount (otherwise known as SMT) electronics, and through-hole circuit boards (meaning circuit traces pass through a plated hole in the circuit board substrate and continue through onto the reverse side of the board). By comparison, the 88/89 was built with mostly conventional electronics where the pins of each device are soldered into a small hole in the circuit board, not simply soldered onto plated pads as is the case with surface mount.

This is important because SMT boards have less surface area for the individual components to solder to, and less of a mechanical bond. Thus, the effects of heat and temperature extremes that are prevalent in a car will cause microscopic cracks in various solder joints that tend to create open circuits, even if only intermittently.

2) The 90/91 clusters also have a problem with burning out the grid and filament high voltage portion of the power supply that provides the voltage to illuminate the vacuum fluorescent display panels. Now, whether this is the result of poor design, slightly under spec'd transistors and capacitors, or something else I cannot say with certainty.

I will speculate that since there is a lot more surface area to be driven on the digital displays in the 90/91 IPC, that the power supply runs hotter than that of the 88/89 design, and that may cause thermally induced failures that are very seldom seen in the early design cluster.

VFD's typically require 60VAC or so for the filaments and a similarly high voltage for the grids in order to get the display segments to fluoresce. The more segments that are lit (and the larger the overall display) the more power is dissipated, resulting in higher operating temperatures. Of course, this has to be taken into account when designing the power supply for the display. Proper component specifications and adequate heat sinking are required to insure reliability in the long term.

I guess I would have to say that GM (Delco) did more than "good enough" since failures have not been too prevalent until the last couple of years. That is an almost 20 year life span for most of these clusters (well beyond the intended lifespan of the vehicle in most cases), and many originals have yet to fail. Then again, I have a few IPC's that were previously rebuilt by a Delco service center (and these have the stickers saying so) that have failed again that are awaiting repair. Go figure.

KDirk

[Bushwack]

Silly question but I'll ask. On the 90/91 clusters, will its life be extended significantly by dimming the unit (10 or 20%)? If heat is an issue, I would assume so but I'm no expert.

..and for future reference, are these units easily replaceable/exchangeable?

[NCReatta]

Silly question but I'll ask. On the 90/91 clusters, will its life be extended significantly by dimming the unit (10 or 20%)? If heat is an issue, I would assume so but I'm no expert.

..and for future reference, are these units easily replaceable/exchangeable?

Dimming will not do anything. Like Kevin said, they're heavily reliant on surface mounts, and vibration and heat (sun and ambient car temp) are the major weak links.

They're very readily available. I have quite a few, as does Steve and others.

[Jim]

Both are digital.

The easiest and quickest way to determine the early from late IPCs is the late ones have "unleaded fuel only" in green on the face.

As to the value of the IPCs in the '90-91 Reattas you should never pay more that about $ 135 for one as they can be rebuilt by digital dash solutions for $ 150 and that includes shipping. You get a guarantee with this rebuild.

There web site can be found on Ronnies site.

[harry yarnell]

The '88-89s have the hard keys horizontal, whereas the '90-91s , they are stacked vertically.

[Guest steveskyhawk]

The quickest and easiest way to fix a bad Instrument Panel Cluster (IPC) is to replace it with a unit that is known to work. I have over 50 tested 90-91 clusters in stock. No need to take yours out and ride around with your car all apart for weeks waiting for the repaired unit to arrive. I ship every day via USPS Priority Mail. Best of all worlds would be to replace your IPC and then send out the original one for repair. It may not even be repairable, who knows.

[Guest Recian]

ya know it being a heat issue the 88/89 models have a vent in the dash behind the IPC for that purpose. The 90/91 dash is thicker around the cluster and doesnt seem to have as much ventalation as the 88/89s did on top of it running hotter could be part of the reason.

[KDirk]

Recian,

There appears to be slightly better ventilation on the 88/89 "pod" that surrounds the cluster, but I have to think it has more to do with the transition to SMT electronics and dual sided circuit board design. Many mid-90's Cadillacs with digital dashes had the same problem with bad solder joints, and these were also SMT based circuit boards. By comparison, the late 80's Cadillac digital dashes (excepting the Allante perhaps, which was a much different beast) were much more solid. This was a transition in manufacturing process that took place in the early to mid 1990's.

While on the subject, I find it remarkable that the CRT in the 88/89 holds up so well. That thing runs HOT! Almost usable as an auxiliary heater in the winter time. Again though, it uses the older style though-hole mounting method for all the electronic components on the circuit board. I really think that is the key difference.

KDirk