John A. Marker

Last week the instrument panel lights went completely blank while driving. They went out for about 15 seconds and then came back on. This happened again later for about 20 minutes and then came back on.

Going through the trouble shooting section of the FSM it indicates that the black wires in the plugs that go into the panel are grounds. Following these wires under the dash, I don't find anywhere that these are grounded to the body.

Could I splice a wire into the black ground the plugs into the panel and run it to a separate ground? What say you electrical experts??

primalurges

If you are certian that there are multiple grounds going into the dash they could be jumped, however if there are multiple grounds its very unlikely that multiple grounds would fail at once causing the dash to go dark. I think focusing on a bad ground is a good idea but the cluster containing multiple grounds doesn't sound right.

John A. Marker

The FSM shows that most of the electrical units in the dash (instrument panel, radio, and others on this circuit) all combine at some point into a single ground.

jfb

First, you should always include what year C4 you are asking help for, they aren't all wired exactly alike.
Yes, you can splice a separate ground onto the ground wire system under the dash but different parts of the dash have grounds in several places and your added ground may not fix the problem.

Rich Silvestris

It's an 85. If the left/right signal indicators light up when the display goes dark, then it is a grounding issue. The Battee site suggests running a separate wire. The destination for the grounds is a stud low on the driver's side of the motor near the oil filter, but good luck getting at it. You might try using electronic contact cleaner on the connectors at the display. If you do run a new ground, please write up your work and the results.

383vett

You can intercept any ground wire and ground it to the chassis if you are not confident that the other end is connected to a good ground. I've used the 2 bolts under the steering column which bolts to metal as a ground for some of my electicals.

HlhnEast

Boy Howdy. JFB was kind enough to help me thru considerable other details on chasing this exact problem to no avail. My problem is in the cluster itself. The power circuits are just as important.

If you truly have a ground wire issue, most likely your directional indicator lights in the display will be shining all the time because it is grounding thru the directional circuits.

Its easy enough to add another ground wire and pick up 3 wires behind the connectors and run it to a known ground. On my 85, and check the FSM wiring diagrams on your year, the B1 wire and on the other the D1 and D3 are all grounds I took 3 pieces of 18 gauge and soldered them on to the above wires. I then soldered these all together to one 12 guage, drilled a small hole in my firewall and put an eyelet crimp connector on it. I had the battery out for the drill and mine had a frame ground right there so I put the new ground along with the others. Nice neat job and frustratingly did not help at all.

If you add the new wire and it doesnt help at least you have eliminated that issue and now have another ground for your display.

Good Luck with it, I am gonna take my display to a local auto electronics shop with the wiring diagrams and let them chase it out. Everything else on my dash is great so I am hoping it will be a whole lot less than a refurbed unit.

John A. Marker

jfb....look a little lower on my post.....1985. Been around awhile and know how important the year is.

Rich Silvestris - Yes the turn indicators work when the panel is dark. I know about the grounds (I think there are 3-4 of them attached to the block) on the rear drivers side of the block. I am not having any other ground/electrical issues, so I don't think the problem is located there. When I dropped in the ZZ4 I tightened these ground pretty good. But I will get under there and double check to see if the nut is still tight.

Willie - I was thinking of using one of the bolts on the column....great minds think alike. The bolt is close to the source and is a solid ground.

John A. Marker

Rich Silvestris gave a hint to this site. Here it is

http://batee.com/corvette/dcrg/index.htm

A lot of very good information here....and reasons to back off at the point of one's own limitations.

This diagram was much better than what I found in my FSM. It might be valuable to you in the future...


So I am going to try and splice a wire to D1 (ground for the instruments) and ground it to the steering column bolt. I will also clean off the contacts before re-assembly.

engle1147

The pin outs for the connector are the same for '84-'89 so no problem with attaching a new ground to D1 at or near the connector.

I got to tell you though if the cluster only blinked or went "dark" on the one drive I wouldn't go digging in to deep. Temperature and moisture can cause issues with electrical connections as well. Before adding additional grounds I'd be tempted to dissassemble the cluster (remove the back PCB also) to check for bad solder issues and clean the connectors. Then see if the problem reoccurs.

jfb

Highlight in red the year of your corvette, "lower on my post". I cannot see it in any post except the one I quoted.

John A. Marker

The dash lights going out have happened several times. I happened once about a two months ago early in the morning. At first I thought I had just blinked. And then a couple of times on one day and three time the next day. It has gone from a quick blink to 10 minutes or more.

Moisture is not a problem, the car is garaged. The times that it happened were not excessively hot or cold. And it was never raining. I just don't want to be running down the road and have it go out and not be able to see a oil/temp/charging problem come up and not have it register on the dash . I have too much $$ in the engine to screw it up because of a ground or if that is not the problem...a bad dash cluster. I will start with the ground and if that is not it then have the cluster rebuilt.

jfb

Unplug the cluster and spray some electrical contact cleaner on the connector contacts and plug them back in. I highly recommend Craig laboratories DeOxit D5 spray.

SunCr

Moisture was a problem on these Years because the Cluster ground, D3, passes through (at the bottom) of the Big Connector behind the battery and above that is the fresh air inlet drain. The seal wasn't terrific and water would get in the Connector (simply washing the car drains moisture in this area) and that water would just remain in the bottom where it would eat away the terminals. D1 is grounded in Driver's Kick Panel and there's a ton of other stuff spliced into that ground circuit, so when it opens, all of that other stuff is going to quit working too. For '89, GM moved D3 (after replacing a bunch of good Clusters) so that it passed through the Firewall with the ECM harness behind the right head (it's outlined in the Electrical Supplement - if you follow the Service Manual Schematic it's got the wrong wiring). For anything before '89, taking apart the Connector and cleaning it up was one remedy. If you do this - and there's enough wiring - bend the harness down so that water can drip off of it and not get wicked up into the Connector. Slather as much dieelectric as you can all over the Connectors and use some window ribbon sealer on the Connector halves. The other, often recommended procedure, was to simply splice D1 and D3 together as D1 is/was allmost always good.

redvetttes

There is a good write up on the darth vader site somebody here should have, I'm on my phone now, it shows how to fix the IP it show a guy who had bad grounds on th bulb circut

86PACER

I've experienced a similar problem a few times myself. But if I tap the cluster it lights up again. Has not done it in a while.

383vett

Tell John to carry a hammer in the console.

John A. Marker

Thanks for the recommendation Willie. I do have a large rubber mallet about 3" in diameter x 4" but I don't think it will go into the console. When I work with steel, sometimes the best thing is just a bigger hammer.....I have one that is 8 pounds on a fiberglass handle about 3'-6" long.....really gets some TORQUE off that one.

Think I will just run the second ground.

joelmatchpoint

Had the same problem with my digital dash cluster occasionally going dark on my '86. After reading Bryan Thompson's article on batee.com I checked continuity between the grounds for D1, D3 and B1 to the chassis of my radio. Discovered that both D1 and D3 had continuity showing they were grounded but B1 didn't. As I already had the bezel off of the information center it was really easy to run a separate ground wire from B1 to the chassis of my radio. Haven't had my dash go dark since.

Cliff Harris

The ground for the dash backlighting is G201. It is located on the hinge pillar, low enough that you have to remove the frame cover and move the carpet out of the way to see it.