Unknown grouding issue 89 Instrument Panel
Thread Starter
Cruising
Joined: Jul 2012
Posts: 14
Likes: 0
From: Ekron Ky
Unknown grouding issue 89 Instrument Panel
Okay, so I know this is a fairly common problem with the digital dash in the C4's that there will be grounding issues (instrument lights going out and turn signal/bright indicators staying on).
I started off with the fairly typical problems, my instrument panel backlighting started going out and if i tapped it with my fist the lights would come back on. After a while the lights eventually went out and stayed out, along with my turn signal lights staying on.
It was around this time about a dozen other unrelated problems started occurring and I ended up parking the car and letting it sit for about a year and a half. I've recently dug back into it and started knocking out one problem after another and have got back to the instrument panel.
I ended up ordering a refurbished instrument panel, put it in and have the same issue.
Eventually I will be cleaning up the factory grounds but in the mean time I've spliced into the 2 grounds coming from the instrument panel connector and ran them to my steering column. Surprise surprise, it's not helping. I also checked the INST LMP 3amp fuse and am not reading any voltage.
Any ideas?
I started off with the fairly typical problems, my instrument panel backlighting started going out and if i tapped it with my fist the lights would come back on. After a while the lights eventually went out and stayed out, along with my turn signal lights staying on.
It was around this time about a dozen other unrelated problems started occurring and I ended up parking the car and letting it sit for about a year and a half. I've recently dug back into it and started knocking out one problem after another and have got back to the instrument panel.
I ended up ordering a refurbished instrument panel, put it in and have the same issue.
Eventually I will be cleaning up the factory grounds but in the mean time I've spliced into the 2 grounds coming from the instrument panel connector and ran them to my steering column. Surprise surprise, it's not helping. I also checked the INST LMP 3amp fuse and am not reading any voltage.
Any ideas?
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
Sounds like the connector between the boards. Look for obvious scorch marks around it. I had this same issue. I ended up soldering a wire on each board with a male/female coupling so I could still separate the boards
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
There are two grounds for the instrument cluster.
One is on the hinge pillar near the driver's left foot. That one is for the cluster lighting.
The other is on the engine block with about 5 or 6 other grounds. That one can be on the side of the block above the oil filter or on one of the bellhousing bolts -- the location changed over the years. This one is for the sensors.
One is on the hinge pillar near the driver's left foot. That one is for the cluster lighting.
The other is on the engine block with about 5 or 6 other grounds. That one can be on the side of the block above the oil filter or on one of the bellhousing bolts -- the location changed over the years. This one is for the sensors.
Thread Starter
Cruising
Joined: Jul 2012
Posts: 14
Likes: 0
From: Ekron Ky
I found out there are actually 3 grounds for the cluster. I've spliced new grounds into each of them and ran them to the bracket support the steering column. Am I right in saying if the ground issue were anywhere other than in the actual instrument panel then this should have done the trick? I'd like to eliminate all other options before I send this instrument panel, that I just bought, out to be fixed again.
Safety Car
Joined: Nov 2008
Posts: 4,328
Likes: 15
From: Jacksonville FL
Also take a look at the main connectors and see if you may have bent one of the pins. Did they rebuild your dash or did they just sell you another rebuilt one? Asking because it would follow if its a new to you dash the problem will be with with your grounds for sure. When I regrounded my '85 I spliced a wire in before the main connector and took it thru the firewall to a new frame ground to be sure it was good. After that is when I did the jumper to fix mine.
Good luck!
Good luck!
Thread Starter
Cruising
Joined: Jul 2012
Posts: 14
Likes: 0
From: Ekron Ky
The dash I bought was another rebuilt one, not the original. I've checked the pins and connectors and they're all fine. I did go ahead and clean them all off with contact cleaner though. I spliced in the new grounds a few inches behind the connector on the dash. I don't see how the ground could be anywhere other than in the dash.
Like I said though, I'm throwing this out there in case there is something that I'm missing or to see if anyone else can think of something.
Thanks!
Like I said though, I'm throwing this out there in case there is something that I'm missing or to see if anyone else can think of something.
Thanks!
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
What pins are these 3 grounds on?
All of the grounds are connected together on the cluster PC board. The ones I know about are:
D1 - goes to G201
D3 - goes to G104
D14 and D15 are connected to ground on the PC board but don't have wires in the connector.
C15 is the return connection for the VSS, but it goes straight to the VSS, which is isolated from ground.
C14 is the return for the cruise control servo position sensor. It is also isolated from ground.
B1 is shown on the cluster connector diagram as a ground pin but it actually supplies a reference connection to the switches on the center cluster panel.
All of the grounds are connected together on the cluster PC board. The ones I know about are:
D1 - goes to G201
D3 - goes to G104
D14 and D15 are connected to ground on the PC board but don't have wires in the connector.
C15 is the return connection for the VSS, but it goes straight to the VSS, which is isolated from ground.
C14 is the return for the cruise control servo position sensor. It is also isolated from ground.
B1 is shown on the cluster connector diagram as a ground pin but it actually supplies a reference connection to the switches on the center cluster panel.
Last edited by Cliff Harris; Dec 4, 2013 at 02:50 AM.
