While replacing my heater core on my 79 L48 I had to remove everything to it take out. Anyone that has done this knows this is one of worst pain in the --s jobs in the corvette world. I have spent close to 26 hours so far. My problem is while reassembling I plugged in the center console gauges and the gauges are not in sinc. I get no temp.,no battery charge, the oil pressure gauge starts at 60 and increases right to 80 when you step on the gas. The gas gauge shows 3/4 tank but it is full. It worked perfect before I took it off but the only thing I have done is cleaned the face plates while it was off and I know I moved the needles. The plug is in right as it goes in one way and I am getting power as the lights work. Any help would be appreciated as I just want to finish this job and get on to the next.

 

Are you SURE you plugged it in the right way???
Sounds like it is plugged in up-side down.
Also, while I was doing my 77 the plug came half way un-plugged and the gauges were all off. Check your plug again.

 

Rotated the needles by turning them, or moved them by physically pulling them off the post?

You can rotate them without problems. If you pulled em off, you have to push them back on at the right spot.

 

Do you have a ground wire hooked up? If bezel is not fully seated it may not be making a good ground which will create strange readings on your guages.

 

Sounds like a ground problem. Look for a ground wire off.

 

if your ground isn't good... then your gauges will give you false readings... make sure the ground is good

 

Sounds like it could be a ground problem, I had a ground problem with my temp gauge and the temp was all over the place untill I found the problem.

 

Thanks alot for the replys. Tonight I will use the tester to check the ground on the plug harness. If it is ok are you saying there should be another ground wire some where attached to the bezel???????? If not and the ground to the plug is ok I would think the circuit board on the back may be screwed although it visually looks fine. Other than that the car was perfect for over a year before replacing the heater core and now

 

I tested the harness plug that goes into the centre console and there is power to all the terminals except the terminal that the green wire goes into. I then clamped the tester aligator clip to the green wire and checked the other terminals and the tester did not light up on any of them. I really do not know what colour the ground wire is????????. I thought it was black and my electrical diagram does not tell you. This part of repairing my car is way over my head.

 

Your black wire is your ground wire. There should be 2 black wires on the connector.

 

As I am not positive what to check to see if I have a bad ground on my plug harness how do I go about it using a tester. What should I clamp to and what should light up and not light up. Not having done this before it is a new learning experience.

 

click here, this guy did a great job of scanning schematics - they're on an 80, but should work for you...

 

I had to go thru the same thing a few years ago. PITA. You will need an electrical schematic. Also, when testing make sure your ground wire for the meter is grounded to clean metal... not rusted or painted metal. Otherwise you won't get a good ground. Certainly sounds like a ground wire. I think the main harness ground is up under the driver side dash or kick panel but not certain.

As you mentioned, you can only plug the harmonica connector one way. It won't plug in if reversed so you can rule that out. Check the printed circuit board to make sure that you don't have any breaks. As they age they become fragile. Moving the needles should not matter. I've moved mine around in circles. Once power is restored to the gauges they align themselves properly.

Also make sure the copper tabs on the harmonica connector and printed circuit board are clean. I had an issue once due to corrosion on the tab. A pencil eraser will clean them nicely. Be careful with the tabs on the printed circuit board. They are fragile. Also, make sure the tabs on the printed circuit board are not bent in such a way that when you plug in the harmonica connector the tab moves and you don't have a solid connection. I actually glued the tabs down (from the bottom side) to keep them from moving around.

One possible way to test the ground wire theory is to ground the gauges seperately from the harness. In other words with the harmonica connector pluged in, run a wire from the ground post on one of the gauges to clean bare metal. If it is a ground issue and you have run a seperate ground but the gauge is energized via the printed circuit board the gauge should function.

 

Thanks for your help and I am sure that when I figure this out I will buy you all a beer. But one last question (maybe). If I hook up one clip on my tester to a wire that I know is hot on the harmonic connector and the other to the ground being black on the harmonic connector and the tester lights up------ does that mean the black wire is a good ground??????