GREGGPENN

Over the past few months, I've observed some electrical gremlins. Gotta wonder if there's something like a ground in common?

Voltage often displays between 11-11.5V. Yet, I can see it instantly JUMP to 13-13.5V. Once the "jump" occurs, it stays there. Sometimes, it doesn't jump. I've had an armature shop test. They said battery AND alternator are O.K. (New battery less than a year ago.)

A/C controller goes blank and/or strobes like an oscilloscope. This started a few weeks after pulling it apart last year. I cleaned contacts -- especially between main board and display board. Bend tabs (out) to increase tension where they connect. It works fine...but the display is whack.

When trying to connect to the ECM, it constantly fails -- when the A/C display is whacked out.

Turn signals are slow...and I can see the slightest dimming of dash lights with each flash.

It's been cranking/starting fine...so I need to check if the voltage is REALLY low (when showing lower 11's). I kinda thought it needed more than 11-11.5V to start...so maybe the voltage meter is part of this voltage gremlin?

IIRC, there's a ground strap down behind/under the A/C controller. Could that affect dash functions too?

Joe C

with that many issues, the common denominator is usually ground or grounds. try running a temporary, secondary ground from the battery-to chassis-to engine block.

question - are you having these issues at idle, cruising speed, cold temps, operating temps - part time or all the time? for some reason, I keep coming back the AC controller, but I wouldn't count out the alternator supply not meeting demand either. exactly what do you mean when you say the AC controller display is wacked? what the current rating of your alternator? did this problem pop-up from nowhere, or was there some maintenance issue that triggered everything?

let me poke around in my 90 FSM - that's the closest thing I have to your 89. i'm curious about this AC controller ground, and system ground distribution.

GREGGPENN

You COULD say it popped up from no where....

I've had problems with both (voltage display and A/C controller) for long enough that I don't remember if anything trigger either. I'm gonna say no EXCEPT that it might have been within a few weeks of pulling the A/C controller.

To be clear, the A/C controller is the "head" unit forward of the console...below the radio. It's where you select heating/cooling functions. I have the computerized version (vs slide controls).

Below each button, there's a small light to indicate if you've selected: Auto, Heat, Bi-Level, etc... There's also a display for target temp, and fan speed. (target temp toggles for outside temp). When it say it's whacked, the bottom row of function lights cycle in a pattern while the temp display flickers so fast, you can't read it. It's almost like a boot cycle! LOL

But, again, the A/C unit still FUNCTIONS correctly. IOW, I can click temp up/down and affect what happens. I can change function/fan speed. Because JUST the display functions are haywire, I figured I lost constant connection between the main circuit board and the display board INSIDE the unit.

The voltage display issue (toggle with coolant temp) has been on/off for a year. I've tested it a couple of times. I've also bought a new battery AND I put it on a charger if it's sat for a week (or more). BEFORE I bought a new battery, it wouldn't start when dropping into the 11's. The armature shop said I didn't drive it often enough -- which contributed to battery issues. (It didn't help that my bodyshop let it run COMPLETELY down 2 summers ago...and left it dead for days and days.)

After buying a new battery, it seemed better. But, then again, it's sat for another issue/two earlier this year. Finally cured and running again, I've seen the weird voltage readings...where it JUMPS 2 Volts at seemingly random times. The last time that happened, I turned OFF the lights, it jumped, then I turned them back on. It jumped from 11.5 to 13.5V and stayed there after jumping.

Weird huh?

The slow turn signals just started. When flashing REALLY slow, I looked at the entire dash for other clues. MAYBE seeing slight dimming with each flash. One of the reasons I went to the armature shop was to see if they could check the regulator. They "rebuilt" it in 2010 when I polished the case. I thought that might be the issue causing weird jumps in voltage display.

I haven't noticed a correlation between voltage (display) and function of the A/C controller...or speed of the turn signals. If the voltage is really fluctuating (from a failing/intermittent regulator), maybe that's the cause.

Of course, the armature shop says $100 to redo again. Cracking into the alternator is "hard enough" that he can't do regulator w/o the whole enchilada in consideration. IIRC, newer, higher-powered units are on eBay for $200ish? (polished/chrome to match). Of course he says they are shoving TOO MUCH in a small alternator case and HE wouldn't buy one.

Rock and a hard place! LOL

GREGGPENN

Oh yeah....

The NEW battery might be why it starts below 12V where it didn't before? And, maybe there IS a combo of regulator (ground?) in the battery COMBINED with being a car driven only here/there.

I used to be able to smack the side of the A/C center console and get the display to go solid. That's obviously indicative of a bad connection/ground.

I could easily have 2 or more issues.

I guess my money is on a regulator AND connection problem INSIDE the A/C controller. If the regulator isn't working properly and/or the car isn't driven/charged often enough, maybe that's why I'm seeing turn signals slow down? Seems like everything would be dimming though....Headlights, dash, etc...

ctmccloskey

Your car sounds like it is having a problem seeing the "real" voltage.

My 1988 Coupe sat for a couple years and when I tried to start it there was nothing, no sounds other than a couple relays clicking. No fuel pump priming or anything.

On my car it turned out to be related to my fuse block. The voltages were low at the fuse block, what I mean was there was about 2 volts difference between the actual battery voltage and what I saw at the fuse block. This was caused by that nice stack of 12 volt wires that are attached to a stud behind the battery but in front of the drivers door. The stud has a wire that comes from the battery Positive connection supplying battery Voltage, the post on my car was badly corroded so I removed the nut and the connectors and cleaned them all up. These connections here at this post supply power to the interior accessories through the "Fusible Links" that attach to the post we cleaned.

The other issue on my car with the fuse block was that the fuses' themselves had corrosion on the Fuse's blades that insert into the fuse socket. I used a meter and found no continuity through the fuses even though they were not melted or fused. After replacing the fuses and cleaning the fuse block with Emory cloth on a small flat bladed screwdriver I found full voltage and my accessories started working again.

While I had my Dashboard apart I cleaned every ground connection and verified that I indeed had full battery voltage at every power wire.

On your C68 (the digital A/C controller) you might want to call and speak with Bryan at BATEE.com. He is the Digital Dashboard Guru who also fixes the C68's and their weird faults. He has the parts and knowledge to help you there.

I hope that this little bit of history might be of use to you! Good Luck and before you know it Your Corvette will be putting smiles back on your face!

GREGGPENN

Thanks!

Now that you mention it, I think someone else pointed me to the wire leading down behind the battery. Might have been in my first post last year (on this subject)?

If that's it, I should LISTEN better! (Though I wasn't aware it was a distribution "link" to interior circuits.)

I'm familiar with Bryan's website and have looked at it 2-3 times over the years. If he can identify the C68 display voltage supply and ground, that could go a long way in finding my intermittent controller connection.

Today, I got in and voltage displayed at 14.1 to start. As I drove around, it dropped a tenth every few minutes. By the time I got back running an errand, my dash showed 13.4V. Turn signals were back to normal today... So...I suppose it could be a distribution block problem.

Too bad I have to remove rocker panel, then side quarter, then battery just to GET to it! That's probably why I didn't jump on that recommendation last winter.

I do have an 89 FSM around here. In the electrical section (in the back), maybe they show that connection under a distribution block page? I'll have to look and see if I can locate what junction diagram. I'm kinda surprised, there would be a separate supply for dash items coming off the terminal of the battery. That seems ODD.

It SEEMED more likely it would come out of the fuse block AND I thought that was fed by the main positive cable. That (apparently false) assumption is another reason I didn't think a SMALLER lead off the battery would feed anything in the dash. I pegged it more for distribution to engine relays/sensors/etc...

Thanks again.

Cliff Harris

I had a problem with my voltage jumping between ~13 volts and ~11 volts. I took the alternator apart and cleaned everything and put it back together. That solved the problem and it hasn't reoccured since (at least 5 years).

GREGGPENN

Any chance you have a sense of what piece you affected during your "clean-up"? Is there an internal ground-to-case or other connection you feel most likely improved continuity?

I looked at a vid on disassembly once. It looks somewhat challenging due to the "electrodes" that have to be cut just to take it apart. IIRC, there might even be a potential "weak" point of the design where/how the regulator connects....making it the likely culprit?

j.martynuska

I had charging issues a while ago - voltage would drop, battery would lose charge. Tried chasing all kind of grounds and power leads. Finally had to cut off and replace the ring lug on the large gauge red wire that attaches to the terminal on the back of the alternator. (hearing my English teacher pounding head over all the prepositions)

For the climate control display, I replaced the electrolytic capacitors on the circuit board. I don't recall the values, I removed them and took them to Radio Shack when one was still open in my area. Cured the display strobing problem. The back lighting goes out, so I think I have an additional grounding issue.

Good luck!