I'm trying to trouble shoot my voltage/coolant temp gauge not showing anything.

My 1984 corvette history is unknown and I think it was was an overheat problem and it melted some wires/connectors. That being said, I'm trying to track down the dash info. I have the FSM and have looked at all the schematics and read through the troubleshooting area and it does not give me info on the voltage gauge. All other gauges seem to work (oil temp/pressure, trip/MPG, etc).

Under the driver dash there are 2 wires melted, drk grn/white and brown. The dark green white from what I understand is the coolant sender from the passenger side block and is used for the radiator fan. And Brown should be that same sensor to the A/C module.

For the Water Temp sensor I have continuity from the (driver side) engine water temp sensor to a green wire past the firewall under the driver dash, but have not been able to follow that. From what I understand that wire is for this gauge. The DIC switch is working, but like I said no lights at the dash.

The car has not run since we've owned it, so I can't test things at temp or anything like that, but to my understanding it should still show LO. I have not got to opening up the dash yet which might just explain it all, but hoping to have some insight before I start digging into that. Having a wire to trace on the coolant is good, but what do I check for the voltage going to the gauge?

Or maybe it's just a bulb in the dash for that gauge? Like I said I have not opened the dash yet.

 

Key on, sensor out (disconnected) you should see LO. Grounded it should max out iirc. My sensor at the block appears to be a baby blue wire but we all know how things get after years... Green seems right according to the FSM. I do not have the electrical supplement but I recall the voltage gauge being piggybacked off the injector fuse...

The idiot light portion should light regardless of switch position. If you ground the sensor wire and get the red light in the top left corner then the data stream is in tact and functional. Does the segment check out okay on its key on test? if so and it goes to a blank screen then I would wager the switch is not working properly. I really need to buy the electrical supplement for the FSM.

 

Looks like red wire for voltage gage source on LCD



Test your sending unit

Couldn't get this one to upload, had to screen shot

For your voltage looks like the red wire from the DIC (multifunction switch) to your instrument cluster, maybe check for continuity between the two, not sure if you can just check voltage or if this is just the "on" for the voltage gage and the instrument cluster gets this value from it's power supply.!?

For the coolant, I would test the sending unit (using information provided) then check the dark green wire for continuity and then again where it changes to dark blue (also through this connection) all the way to the instrument cluster. So if that all checks out, I would guess the instrument cluster LCDs for this display has issues (cold-solder, bad, bulbs, etc.)! Hopefully this helps, good luck👍

Tells the inputs, note voltage inputs

Testing sending units

 

Looks like there is damage to the glass, anyone looking to sell just the glass???

Seems backwards to me that my instant and MPG were working, but the voltage/coolant wasn’t.

 

Check out batee for that.

 

I knew that was going to be the answer, ordered. Btw, I posted a build post as you requested in your PM, but it said it needed to be approved by the admins. Guess it was too long or something.
thanks again.

 

Any time. And yeah... if it weren't a real 84 dash you can find the center used but that gauge section is 84 only... kind of hard to find sadly. On the bright side it'll come ready to go. Since mine is good I am not giving it up lol.

Strange about the build thread... was it here or in another section? I only say to do it because it's cool and it gives others motivation to do theirs too. Let me know when you want that bin... I'll go back and find it. Just been a little busy.

 

Hello, My Corvette did that on some of the gauges. The light bulbs burned out and I pulled out the instrument panel and replaced all the bulbs. The bulbs had two metal plug ins you push into the dash panel. It worked good for a short while and one day they all went out again and never worked again. I bought some after market gauges and hooked them up and still working good. The instrument panel used was about $400 and the aftermarket gauges were less than $50.00. I only replaced the tach and speedometer with budget gauges years back still working! This is a picture of my car it cost $6,500. Best of luck to you!

 

I'm going to bump this because I have a question. In the picture above showing the voltage checks there is beside the coolant temp value a "D4" I suspect that it is some kind of pin location somewhere but I would like to know where.

 

My apologies for not responding to this on fb or here, but I was supposed to get my coolant lcd on Saturday, but UPS didn't make it (I should get it today). I see on fb you were able to resolve this. Please post your solution here so others can learn from our troubles.