Ground wire
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
Ground wire
I am having problem with my alternator and oil pressure gauge way to the right and the tachometer is not working at all. Everything started going weird after I changed the body mounts out. The alternator and oil pressure work but it says that I have over 80psi for oil pressure and I am putting out about 17volts from the alternator which I now are both false.
I think I may have found the problem but not sure. There are two ground wires that come off the frame down under the vapor canister. The skinny one goes from the frame to the vapor canister bracket and is connected. There is one wide one (about 3/8s wide) that is broken and hanging from the frame. Does anyone know where this goes?
I have checked all my connection on the gauges and wiring harness in the dash and no luck. Any ideas???
Thanks
Dan
I think I may have found the problem but not sure. There are two ground wires that come off the frame down under the vapor canister. The skinny one goes from the frame to the vapor canister bracket and is connected. There is one wide one (about 3/8s wide) that is broken and hanging from the frame. Does anyone know where this goes?
I have checked all my connection on the gauges and wiring harness in the dash and no luck. Any ideas???
Thanks
Dan
Burning Brakes
Joined: Jun 2003
Posts: 1,079
Likes: 1
From: Niagara Falls ON
The gauges need ground to work.
Not sure if what is in here helps:
http://forums.corvetteforum.com/c3-t...-firewall.html
Not sure if what is in here helps:
http://forums.corvetteforum.com/c3-t...-firewall.html
Melting Slicks
Joined: Aug 2001
Posts: 3,047
Likes: 124
From: Wichita KS
... There are two ground wires that come off the frame down under the vapor canister. The skinny one goes from the frame to the vapor canister bracket and is connected. There is one wide one (about 3/8s wide) that is broken and hanging from the frame. Does anyone know where this goes? ...
Also connected to the frame at the #1 body mount location is a ground lead for the forward lamp harness. That ground wire should run from the frame (driver's side #1 body mount) up into the forward wiring harness at the fuse panel.
For 1980, the relevant A.I.M. pages are UPC A01 to A12 sheet 37 and UPC 12H sheet 1.
Last edited by mapman; Apr 13, 2012 at 02:42 AM.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
Well the ground wire between the frame and birdcage was broken from when I pulled the body mounts. Installed another ground wire but it did not fix the problem. I guess I will pull the gauges again and see if there is a problem back there....
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
I pulled the gauges and nothing appeared to be defective and I could not find any loose wires. Is there anyway that I can run a ground from one of the gauges to the body to see if this is the problem? If so, where should I connect it on the gauges? Again, the problem is the fuel gauge, voltage gauge and oil pressure gauge all go way over to the right when I start it up. They are still working (they do fluctuate) but way to far over to the right.
When the car is off and I turn the key, I read about 13 volts and when I start it up it reads almost 18 volts. With the oil pressure it is about 40 psi and then up to 80 when it is started. Everything else works fine on the car........
Dan
When the car is off and I turn the key, I read about 13 volts and when I start it up it reads almost 18 volts. With the oil pressure it is about 40 psi and then up to 80 when it is started. Everything else works fine on the car........
Dan
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Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
I know very little about the electricals on the later C3's...but, the gauges need a ground, too. I suspect that the ground connection going to the gauge circuit board/tach circuit board is missing/damaged/etc. On an early C3, you could touch a 'good' ground wire to to metal area on the gauge bezel to see it that was the problem. With a plastic bezel on the later vintage cars and the circuit boards behind it, I'm not sure how you can easily check for a grounding problem.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
I have a new circuit board on the way so i am going to see if that was the problem....I am really lost on this one. The back of the gauges are on a metal frame. Maybe I will touch a ground to that and check it.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
Well I got the new circuit board for my gauges and it did not help the problem with my gauges deflecting to the right. Any ideas? Could I run a different ground somewhere?
Dan
Dan
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
I am really need of some help here guys. Any idea of what my problem could be. I have looked every where and can't seem to find a loose wire or missing wire.
Thanks
Dan
Thanks
Dan
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
The instrument harness ground should be on the "A" pillar inside, above the hood pull, under the dash. It's hard to see and get to. All the original grounds are black wires.
There is nothing keeping you from adding more grounds from the frame to the birdcage inside and continuing to various parts from there.
The alternator voltage of 18v, if checked at the battery post on the alternator is not correct and sounds like a separate issue. Max should be approx 14.7v running.
There is nothing keeping you from adding more grounds from the frame to the birdcage inside and continuing to various parts from there.
The alternator voltage of 18v, if checked at the battery post on the alternator is not correct and sounds like a separate issue. Max should be approx 14.7v running.
Pro
Joined: Feb 2012
Posts: 668
Likes: 21
The alternator voltage of 18v, if checked at the battery post on the alternator is not correct and sounds like a separate issue. Max should be approx 14.7v running.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
I checked the voltage with the key on (car not running) and it measured 11.4 volts at the alternator. The gauge is still pegged to the right along with all the other gauges except the temp. I measured zero ohms between the ground on the a pillar by the hood release and on the ground on the back of a couple of gauges. I have a brand new ground between the frame and body down by body mount # 1.
I also checked and wiggled all the wires that I could see under the dash and in the engine compartment and no luck.
I also checked and wiggled all the wires that I could see under the dash and in the engine compartment and no luck.
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
I checked the voltage with the key on (car not running) and it measured 11.4 volts at the alternator. The gauge is still pegged to the right along with all the other gauges except the temp. I measured zero ohms between the ground on the a pillar by the hood release and on the ground on the back of a couple of gauges. I have a brand new ground between the frame and body down by body mount # 1.
I also checked and wiggled all the wires that I could see under the dash and in the engine compartment and no luck.
I also checked and wiggled all the wires that I could see under the dash and in the engine compartment and no luck.
Thread Starter
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
I used a wiring diagram from WILCOXX and verified that all my grounds are actually good ( back of the gauge to the body was zero ohms). Wouldn't this mean that my grounds are good? I even measured across the back of the amp gauge and read 11.4 volts just like on my alternator and battery. This with the car not running and key turned onto accessories.
Could this mean that maybe I shorted all my gauges out at some time and they are not working at all?
Could this mean that maybe I shorted all my gauges out at some time and they are not working at all?
