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I recently replaced the resistor on the back of my fuel gauge in my '77, which solved that problem. After reassembling, I lost my power windows, gauges and most of the instrument cluster. I replaced the gauges fuse and the 30A breaker after reading some other info. Right now, I have nothing except the radio when I turn the ignition switch to on. When I fire up the engine, I get the fuel gauge and GEN light (and I assume Water Temp gauge, but I haven't let it warm up enough to tell). Even the volt gauge doesn't budge, but the interior/dome lamps are still working. Any ideas?
Last edited by amvenne; Apr 10, 2020 at 06:57 AM.
Reason: added year
Ok. Sorry about the delay. I'm overseas and I had to work today. Gave this some thought, haven't had my dash apart in a couple months. Only ground to frame I can remember is on left hand side. G.M.electrical manual confirms this.
and.
in second photo you can see the ground ring terminal just left of the letter H in headlight.
in first photo it says just above courtesy light.
This could be loose or broken. I'd check the connector on the gauge cluster panel first however.
If you're going to keep this car, you really need to get one of these.
Can't tell you how many times over the years I have looked at this. Makes all the wiring circuits simple.
Ok. Sorry about the delay. I'm overseas and I had to work today. Gave this some thought, haven't had my dash apart in a couple months. Only ground to frame I can remember is on left hand side. G.M.electrical manual confirms this.
and.
in second photo you can see the ground ring terminal just left of the letter H in headlight.
in first photo it says just above courtesy light.
This could be loose or broken. I'd check the connector on the gauge cluster panel first however.
If you're going to keep this car, you really need to get one of these.
Can't tell you how many times over the years I have looked at this. Makes all the wiring circuits simple.
thanks so much for the detailed response! I’m going to look at this Sunday evening when I get home and I’ll let you know what I find. Thanks again!
Update: I checked the fuses this morning and I have power to both sides of the guages fuse. So the problem must be somewhere downstream of that. I still cant find the ground location that was described above, so I'll keep looking for that.
Well it looks like I may have surpassed my ability level. I prefer to do as much work as I possibly can before I have to take it in, but I dont think I'll get this one solved on my own. Looks like a trip to the local corvette shop is in my future.....
When you reinstalled your center gauge cluster did the main plug go all the way back in? When I replaced my heater core a few years back my plug didn’t latch properly, it wasn’t making perfect contact with the circuit board.
Well it looks like I may have surpassed my ability level. I prefer to do as much work as I possibly can before I have to take it in, but I dont think I'll get this one solved on my own. Looks like a trip to the local corvette shop is in my future.....
I would love a pic of said ground, going to pull the seat an be more committed tomorrow. I too am chasing electrical woes...
You need to pull left side dash assembly out, or at least back to access the ground wire screw. Into left door piller. Just left of speedo center line. Didn't think to take a photo last time I had my dash apart.
When you reinstalled your center gauge cluster did the main plug go all the way back in? When I replaced my heater core a few years back my plug didn’t latch properly, it wasn’t making perfect contact with the circuit board.
I double checked it today, and I'm pretty sure it's all the way back in. I can still get the GEN light and fuel gauge to come on. The things not working are the power windows and speedo/tach. The turn signals still work, but I'm pretty sure they are fed through a different cluster of wires. Also, the water temp was reading all the way to the right (hot) right when I turned the car on. Not sure what that's about.
I would love a pic of said ground, going to pull the seat an be more committed tomorrow. I too am chasing electrical woes...
I may try to get back in to this in the next couple days, since I wont be able to get it into the shop for a while anyway. If I do, I'll see if I can snap a pic.
On mine one of the connections on the circuit board got folded over and then the plug didn’t fully seat. It caused all kinds of weird things with various things not working such as the voltage gauge, if I turned on the headlights it worked if I turned it off my generator light came on. I knew it was something I had done as it all worked prior to this.
I would love a pic of said ground, going to pull the seat an be more committed tomorrow. I too am chasing electrical woes...
The first image shows where the ground is, best I could do without removing the Left side dash. The second image is the correct angle but it's a little dark. Unfortunately mine still appears to be well grounded and not frayed, so I'm no closer to having the problem solved....
Red arrow shows where the ground i located, behind the dash. Poor lighting, but you can sort of see the ground bolt.
I thought I'd give it another whirl since I had some free time this morning. I'm throwing in the towel. The ground looks ok, the fuses are fine, and yet I have no power to gauges, instruments or power windows.
If you have a GEN Light and the fuel gauge works you have ignition switch power to the gauge cluster, pin #11 (pink wire).
I would pull your gauge cluster again and check your gauge cluster harness plug at pin #1 & pin #9 for a good clean ground connection to the printed circuit board.
The gauge cluster plug is divided into 2 half's, each half has its own ground (pin #1 & pin #9).
The Main Dash Harness ground starts at the sheet metal screw shown in your photo & on page 28 photo shown above.
From the Main Dash Harness ground you will see S225 S=splice, and lands at pin #1 & pin #9 of the gauge cluster plug (see 2 drawing below).
Page 20 of the 77 Electrical Trouble Shooting Manual
Last edited by bmotojoe; Apr 19, 2020 at 09:53 AM.
The image of the numbered printed circuit board is incredibly useful. Where did you get that from? I'll double check those pins and their connections this afternoon. Thanks!
The image of the numbered printed circuit board is incredibly useful. Where did you get that from? I'll double check those pins and their connections this afternoon. Thanks!
I scanned a image of the printed circuit board, Used MS-Paint to apply the numbering. Helps to have both the 1977 Corvette Electrical Troubleshooting Manual and a Late build spare 1977 Main Dash Wiring Harness laying around...
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