91' Rivi - Digital Dash AND Climate Controls go out intermittently at the same time

[Guest RynoLanerz]

Many years back, I had my digital cluster dash replaced with a Refurb. It started intermittenly, and then of course over time it went out completely. Over the last year or so, it has started up again with my current dash, BUT, this time around when it happens my climate controls also won't work. It will just show dashes on the temp display and won't let me operate any of the buttons. Any ideas? How are these two things related? I am pretty positive I didn't have climate issues the last time this happened... Thanks.

[RivNut]

Welcome to the forum. I don't think there are too many owners of Rivieras with the digital cluster on this forum but there are a bunch of really knowledgeable guys on the Reatta forum who deal with this stuff daily. They can probably answer your questions faster and more accurately. You can also do a search of previous posts. On the right hand side of the dark blue banner at the top of this page, is a link to the 'Advanced Search' feature. Click on it and when you get to the search page, open the tab for a single content search. Type in what your looking for in the key word line - intermittent digital dash - and then scroll down and select the Reatta forum (if you don't limit your search, the search will look through every year, make, and model.) Then click on the search button. There will probably be a lot of threads show up. Just start reading them and see what you can find. If your question isn't answered, then post a new thread on the Reatta forum.

Good luck and let us know what you find out.

By the way. Are you a member of the Riviera Owners Assn? If not, check out the link to their website; it's in my signature block.

Ed

Edited May 8, 2015 by RivNut (see edit history)

[MCHinson]

Rynolanerz,

Welcome to the AACA Discussion Forum. I am not an expert on 1991 Rivieras. I have personal experience only with 1981-1985 and 1986-1989 Rivieras. I am thinking that the two issues are not related. Do you have a factory service manual? The factory service manuals are usually a great help on troubleshooting these types of problems.

Rivnut,

I could be wrong but didn't the Graphic Control Center, often referred to as the CRT, only appear in 1986-1989 Rivieras? I am thinking that he is referring to a digital dash cluster, as opposed to an analog dash cluster. I would certainly agree that the Reatta forum is the home to experts on a CRT screen but I don't think that is what his problem is.

[RivNut]

Very possible. I saw the word digital and didn't think of anything other than a CRT. I have a '90 and a '93 and I guess that I wouldn't refer to them as digital. But in thinking about it, I don't know what I would call them.

Ed

[Guest RynoLanerz]

Thanks for the replies, guys. My riviera does not have the computer climate control, it's the electronic. Only my dash is 'digital', or computer, I guess you would call it. I'm pretty sure it was called the digital cluster?

MCH-They must be related somehow, because when my dash goes out, so does the climate!

I posted a couple pictures. This is my setup. I don't have a picture of the issue happening, but the dash reads 00 and electrical error (which is what happens when it goes out), while the climate controls will read dashes ( - - -) and aren't operable.

[MCHinson]

I would suggest you get the factory service manual. I suspect you will find a shared power source or some other common point in the wiring for those two components. Without a systematic troubleshooting method based on the service manual about all anybody can do is guess. The manual should help you fix it without just throwing expensive parts at the problem(s) while guessing.

[DAVES89]

I have extra Buick shop manuals. Also the climate control unit can be cleaned. There is a "How To" on Ronnie's site [Reatta Owner Journal] for cleaning the Climate Control unit. I believe you should check the plug connections on the back of each unit. After 25 years the connections may need cleaning.

However I believe your Instrument Cluster is failing and that while the two issues seem to be related it is just a coincidence.

You can reach me at lemke1044@aol.com if you want a manual. They are in like new condition and are $75.00 delivered.

BTW if you want to remove the trim panel it is fairly simple. There are two #15 torx screws [one in each heat/a/c vent]. Then grasp the trim panel in the instrument cluster area as the panel is held in place by what I call friction clips and will pull out. There used to be two torx screws above the Instrument Panel to hold the trim panel but I believe that was changed after the 1990 model year, but you should check first. Also be sure you get your fingertips under the silver as these panels are two part jobs and will break.

Edited May 9, 2015 by DAVES89 (see edit history)

[dship]

Quote from DAVES89: "Also the climate control unit can be cleaned. There is a "How To" on Ronnie's site [Reatta Owner Journal] for cleaning the Climate Control unit. I believe you should check the plug connections on the back of each unit. After 25 years the connections may need cleaning.

However I believe your Instrument Cluster is failing and that while the two issues seem to be related it is just a coincidence."

Agree X2.

[RivNut]

I think the screws two screws above the instrument panel are still there in '91. At least they're there in my '93. Some lazy guy just didn't put yours back in the last time the cover was off.

Ed

[Guest RynoLanerz]

Thanks, but I do have an original service manual and also a haynes manual. I'll take a look through 'em. I just have pretty basic car maintenance knowledge. I was hoping by scouring the internet and asking questions, I would find someone who had the same problem and know what it is or have certainty of how the two are related. Recently, I narrowed down an issue with the wife's vehicle, likely saved hundreds and hundreds of dollars by cracking down the internet and doing it myself. So there's always hope!

I don't buy that it's a coincidence, because that would be astronomical odds. Of the 5 or 6 times this has happened, (anywhere from 5 seconds to 5 minutes), dash and climate have both went out simultaneously, and as soon as the dash comes back, so does the climate controls!

MCH - Probably right. There must be a shared power source or common wiring. Maybe that's what needs replaced, or cleaned.

[NTX5467]

While you're looking at connections and such, you might ALSO check the Body Control Module plug-in. That could well be the "shared power source" as that processes the instrument panel cluster data and also very possibly processes the requests of the HVAC system "input devices" and also monitors what happens after the requests are made.

Where are you located and how is the humidity in that locale?

I know you're trying to conserve financial resources, BUT it might be a good investment to pay the dealer an hour's labor diagnostic charge for them to hook up the GM-spec diagnostic equipment to see what might really be happening.

"Cleaning" terminals can usually be done just by unplugging and plugging-back-in the connector body several times. Many of the terminals are small and fragile. You CAN possibly disassemble the connector and wiring, but all which might be accomplished is to see if the crimps are still solid, between the terminal and the wire itself, and not corroded/degraded/show signs of 'high resistance"/heat.

ALSO, ensure that ALL wiring harness connections at the bulkhead connector are clean and solid, on both sides. AND that there are no issues with the alternator wiring/battery connections/wiring.

What you find in the Haynes manuals will be "representative", but not always "application specific" as the GM manual would be. Please keep us advised of your progress.

NTX5467

[Guest RynoLanerz]

I'm in New Mexico, so we typically have low to no humidity.

 

I'll look into the possibility of the GM dealer diagnostic equipment, good idea.

 

Appreciate the other advice.     

[DAVES89]

The '87-89 Riv and the '88-89 Reatta have a CPS [Central Power Supply]. I believe the CPS is no longer present on the '90 and newer Rivs/Reattas. I have experienced the Instrument Panel going dark, but never the Climate Control. It could be the BCM plug but then I would think you would experience other failures as well.

[KDirk]

90 models also have a CPS, it was omitted beginning with 1991 cars. This looks more like an intermittent data line loss, as the IPC is remaining powered but is getting no data to display. Note that all 86-93 Rivi's and 88-91 Reatta's have a system in which the BCM is the master device controlling the data bus and it supplies all information displayed by the IPC as well as the climate control panel. A loss of data line will cause exactly the symptoms you are seeing here.

The loss of data can be due to an open, a short to ground, a short to voltage or a module failure that is breaking continuity. Most modules have two data line inputs for redundancy (the data line is effectively wired as a loop) so if there is a break at one point, data can still be sent/received from the other direction of the loop. More than one break, or a short to voltage or ground will not be overcome by this redundancy.

When your IPC and climate displays fail, does the climate control default to defrost mode (dash top vent) on high fan? This also typically found to be the case when the data line is down. Some troubleshooting will be required here, as it could be damaged wiring, a flaky connector, a bad BCM, bad IPC, bad climate control or almost any other module disrupting the network. Does this typically happen when hitting a bump or is it truly random?

Does normal function return on it's own after a random period of time, or not until the car has been shut off and allowed to sit for a while? The latter would be a possible indicator of a thermal problem in the electronics somewhere (while operating something heats up enough to cause an open circuit only to self-correct after cooling off again). These are challenging faults to nail down due to the number of components involved and the intermittent nature of the failure.

KDirk

Edited May 14, 2015 by KDirk (see edit history)

[Autry]

On 5/9/2015 at 12:07 AM, Guest RynoLanerz said:

Thanks for the replies, guys. My riviera does not have the computer climate control, it's the electronic. Only my dash is 'digital', or computer, I guess you would call it. I'm pretty sure it was called the digital cluster?

MCH-They must be related somehow, because when my dash goes out, so does the climate!

I posted a couple pictures. This is my setup. I don't have a picture of the issue happening, but the dash reads 00 and electrical error (which is what happens when it goes out), while the climate controls will read dashes ( - - -) and aren't operable.

 

[Autry]

My car has the same dash my temperature gauge disappears causing ac to stop working it's driving me nuts