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How can I tell if the printed circuit is bad on the 1980 tach and console guages or if there is a wiring problem?
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22720
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
First, Welcome to the Shark Tank!! 
Do any of the gauges work? The tach board is separate from the console gauge board, so if all of them are not working, I would be looking at a wiring problem(ground), or possibly a fuse/fuse link.
I can send you a wiring diagram, if that would help. It does have the schematics for the circuit boards, I think...
It does have the console gauge board. The tach board is actually mounted on the back of the tach.
P/M me with an e-mail address, and I'll shoot ya the diagram.
A lot of times, when the tach doesn't work, it is the filter, by the dist. If you unplug it, and the tach works, the filter needs to be replaced. It is in/on the white wire, and supplies the rpm signal to the engine computer.Adams' Apple 2006-11-13 20:26:46
Do any of the gauges work? The tach board is separate from the console gauge board, so if all of them are not working, I would be looking at a wiring problem(ground), or possibly a fuse/fuse link.
I can send you a wiring diagram, if that would help. It does have the schematics for the circuit boards, I think...
It does have the console gauge board. The tach board is actually mounted on the back of the tach.
P/M me with an e-mail address, and I'll shoot ya the diagram.
A lot of times, when the tach doesn't work, it is the filter, by the dist. If you unplug it, and the tach works, the filter needs to be replaced. It is in/on the white wire, and supplies the rpm signal to the engine computer.
Joel Adams
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Thanks for the offer, but I have a wiring diagram and as best I can tell there should be a white wire from the tach to the distributor. This was unplugged so after scrounging around found what could be a white wire from the harness, but it also could be brown or yellow. I plugged it in and tach is still stuck at 4k and moves very slightly when the car is turned on. The center gauges, oil stays pegged at max, temp doesn't seem to work, ampmeter works, gas works. If there is a way to test these before I spend money on printed circuits or gauge rebuilds I would prefer to do that.
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22720
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
This may be silly, but...have you checked the fuses? The tach normally sets at 3-4000 when the key is off, I think. When it is powered(key on) it should go down to read correct RPMs. The other gauges not reading correctly would tend to support a no power/ground issue. Then again, it could be a problem in the ign. switch.
I'd suggest a good check of all the fuses with a meter/test light, before condemning the boards. As I said, the two gauge packs use separate boards...hard to believe they would both go bad at the same time, or that one bad one would effect the other.
I'd suggest a good check of all the fuses with a meter/test light, before condemning the boards. As I said, the two gauge packs use separate boards...hard to believe they would both go bad at the same time, or that one bad one would effect the other.
Joel Adams
C3VR Lifetime Member #56
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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a
have you taken the console out...then you can check with a multimeter or maybe you can already see if some on the "wires" are broken on the circuit
the console with the temp, oil , clock etc gauges is quite easy to get out... one big plug on the back and don't forget the one on top ( light on console)
art-corvette
the console with the temp, oil , clock etc gauges is quite easy to get out... one big plug on the back and don't forget the one on top ( light on console)
art-corvette
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Send PMGreensburg, IN - USA
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Vette(s): Previous: 1984 Coupe, 1988 Maroon Coupe, 1989 Coupe, 2001 Roadster Present: 1967 Stingray Roadster, 1976 Stingray Coupe, 1989 Roadster..
[QUOTE=Adams' Apple] First, Welcome to the Shark Tank!!
Do any of the gauges work? The tach board is separate from the console gauge board, so if all of them are not working, I would be looking at a wiring problem(ground), or possibly a fuse/fuse link.
I can send you a wiring diagram, if that would help. It does have the schematics for the circuit boards, I think...
It does have the console gauge board. The tach board is actually mounted on the back of the tach.
P/M me with an e-mail address, and I'll shoot ya the diagram.
A lot of times, when the tach doesn't work, it is the filter, by the dist. If you unplug it, and the tach works, the filter needs to be replaced. It is in/on the white wire, and supplies the rpm signal to the engine computer.[/QUOTE]
Hey bro can ya fire me that diogram? My tach haint nair worked. I'm a workin on da C5 raight now but hit haint gonna tak me all winnter.
thankee! Tux...
Do any of the gauges work? The tach board is separate from the console gauge board, so if all of them are not working, I would be looking at a wiring problem(ground), or possibly a fuse/fuse link.
I can send you a wiring diagram, if that would help. It does have the schematics for the circuit boards, I think...
It does have the console gauge board. The tach board is actually mounted on the back of the tach.
P/M me with an e-mail address, and I'll shoot ya the diagram.
A lot of times, when the tach doesn't work, it is the filter, by the dist. If you unplug it, and the tach works, the filter needs to be replaced. It is in/on the white wire, and supplies the rpm signal to the engine computer.[/QUOTE]
Hey bro can ya fire me that diogram? My tach haint nair worked. I'm a workin on da C5 raight now but hit haint gonna tak me all winnter.
thankee! Tux...
Tuxblacray: She's Back In Black! Check out my pics @ My Link 
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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22720
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
no...
Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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Just a quick note on the O/P reading at MAX - mine did the same thing and it was the sending unit. BTW - if you go to the stupid auto parts stores, they will often look up the Vette and give you a sending switch (for an idiot light). The sensor for the guage looks like a small beer can. Best to take in the old one to compare.
C3: 1979 Corvette Coupe, Auto, L-48, Red/Doeskin (my wife's fave);
C4s: 1986 C4 coupe (SCCA road race car), satin black, 4+3, Z51 package, L-98; & 1993 C4 coupe, white, 6-speed, LT-1.
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Send PMGreensburg, IN - USA
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Vette(s): Previous: 1984 Coupe, 1988 Maroon Coupe, 1989 Coupe, 2001 Roadster Present: 1967 Stingray Roadster, 1976 Stingray Coupe, 1989 Roadster..
[QUOTE=sfindlan] Just a quick note on the O/P reading at MAX - mine did the same thing and it was the sending unit. BTW - if you go to the stupid auto parts stores, they will often look up the Vette and give you a sending switch (for an idiot light). The sensor for the guage looks like a small beer can. Best to take in the old one to compare. [/QUOTE]
Mine did OP gauge did the same thing and you are dead on about the auto parts dude. I went to a Car Quest store and that is exactly what happened. Unfortunitly I didn't take the 1st one out prior to going because I was out of town when it decided to start puking oil out of the end. So I had to drive back to the store and they were out of the right one. He was good enough to make a few calls for me and locate one for me so it worked out.
Mine did OP gauge did the same thing and you are dead on about the auto parts dude. I went to a Car Quest store and that is exactly what happened. Unfortunitly I didn't take the 1st one out prior to going because I was out of town when it decided to start puking oil out of the end. So I had to drive back to the store and they were out of the right one. He was good enough to make a few calls for me and locate one for me so it worked out.
Tuxblacray: She's Back In Black! Check out my pics @ My Link
(Click on image to see a bigger version)
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Send PMHOWELL, NJ - USA
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Vette(s): 1979, Targa Blue (72 Color), Pace Car rear spoiler, L88 hood, Dark blue factory interior, 525HP 406, HD 700R4, 370 gears,Steeroids, composite rear spring, TT IIs wrapped in T/A Radials.
The tach board (which is a pc board) is often the culprit - but not always. It was a gamble in my C3 as well as a few friends - we were 100% successful. In every case, the tach seemed to "float" around a certain RPM and bounce a litttle in reaction to RPM. Replaced the tach board and worked like new. The tach board is a $60 investment and can be replaced by taking the tach out from the front of the dash. No contortionist work under the dash for this one....
But, like I mentioned, definitely a bit of a gable unlesss you are very confident that your wiring is good...
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