Started car this evening (after buying wife a dozen roses!) and noticed the tach sitting below zero. Noticed it working this morning. What happened? No playing around under hood lately, so rule out me messing with a wire. Anyway, checked the wire from the distro to the capacitor to through the firewall. All OK. So, where do I check. Notice that the tach needle will bump a little when I turn on the key, but then just sits there. Oh, its an 82.

 

could be the little curcut board behind the tach?

I hear horror stories about 'dem.

Daniel

 

the cable to the tranny is broken. :yesnod:

 

I didn't think the tach had a cable to the tranny. :confused:

I thought only had one to the distributor in pre-74(???) cars, and after that is was just a electric line going from the distributor...

??

Daniel

 

ooooo, you might be right. i have a 79 and that was the answer to my broken tach. i didnt even think to see what year he had. duhhhh. mabey he has a different thing :smash:

 

Yup Tach board. About a $75 part, give or take. I know it is a bear of a job in my 76, but at least my dash is basically 3 pieces. You have to take out the speedo/tach cluster and it is behind and inside the tach.
Go to this web address: http://www.zip-corvette.com/index.htm
That is the Zip tech, either do a search or scroll though the lists, I found a real good step by step how to there with pictures as well
Good Luck
JoeB

 

Thanks, went to the ZIP site. Looks like the repair series in on a 68-77 tachometer. I think the 82 is a little easier to get to. Or, at least I hope it is. And, will probably just replace the entire tach rather than the circuit board. But, I think the tach is gone south, not anything else.

 

Wait..... before you order a new tach or circuit board check one other thing. My tack just quit one day on my 80. I pulled the tach and cleaned all the electrical connections between the tack and circuit board with a pencil eraser and some electrical spray. Guess what, it has worked perfectly ever since. Remember how old your car really is. All the electrical connections corrode over time. A good cleaning can do wonders. I have cleaned all my instrument gauges, circuit boards and light bulbs this way with great success. It cost nothing to try this and just may solve you mystery.

Regards,

Jim

 

If it's a '77 with the OEM HEI ignition, there is no cable. Also, the cable from the tranny is for the speedo, not the tach.

 

Is it difficult to get the tach out of the dash cluster. I have had the cluster loose so I could nip off the pin right after 85mph on the speedo so I can guess how fast I may be going at times. But that was a few years ago. Do not remembler if the entire thing lifts out somewhat to disconnect the guages or is it a b***h to get at. May give it a try this weekend.

 

Its been awhile since I've been in there but usually I can have my cluster out in about 5 minutes. You will have to lower the steering column which is only two bolts just under the dash. You may also have to loosen the steering column nuts at the floor board. If your not sure which bolts and nuts I am refering to, look at your shop manual. Once that is done, start removing the screws around the gauge cluster. First you remove the lens cover, then the cluster itself. You will have to reach behind and disconnect the speedometer cable which is very easy once you position your body on the floorboard. Then start pulling the cluster out. Once you have it out a little, disconnect the wiring harness to the circuit board from behind. If need be, perform a continuity test on the circuit board to look for any broken parts. I was able to fix the "idiot" low gas light mini circuit board by soldering a broken connection. When you start to clean all the connections on the circuit board, you will see how corroded they really are. They will go from a dull copper color to a very shiny and bright copper color. That will give you some indication of how corroded they really are. I can only imagine how many people have spent tons of money on new gauges and circuit boards when all they needed to do was clean it all up. Also while in their, check all your light bulbs for proper function. I simply remove the bulb, clean it with the pencil eraser and some electrical cleaner spray and perform a continuity check with my tester. You will see a little wire on each side of the bulb. If no continuity, the bulb is bad. I could actually read my instruments at night when I got all the bulbs working properly. Good luck. Please post your results.

Regards,

Jim

 

my 1980 does the exact same thing..it bumps when i start the car but doesnt work..it is my next project so please let me know what solution worked for u ..thanx,mark :D

 

How do you disconnect the speedometer cable from the speedometer? Is there a clip?

I'm rebuilding my tach and speedo pretty soon and am curious.

 

Andrew,

It's easy. There is a clip on the back of the speedo that positively locks the cable to the gauge. Once you contort your body on the floorboard to be able to reach up under the dash to get you hand to the back of the speedo gauge, just push down on the clip and pull on the cable at the same time. Kind of tricky at first.

Regards,

Jim

 

Anybody ever wonder about that "speedo" cable being so easy to disconnect MAYBE, just MAYBE one reason why you see alot of the "older, low mileage Corvettes" around. Hmmmmmmmmmmm......... :confused:

 

Paul,

Very interesting point.

Regards,


Jim

 

Well, took the instrument cluster off today. Not really that hard. Just a bunch of screws and cover pulls off. Then, tach is held in place by three more screws. Just lifts out. Cleaned up everything, but could not tell what might be bad. Assume it might be the board, because there was one area that looked darker that rest of area. Don't know first thing about continuity testing so nothing done there. Replacing board should be easy, so off to ZIP Products next. Side benefit, found two cluster lamps out, so replaced those.

 

Can any of you guys with the electric tachs tell me how to wire mine up. I'm converting from cable drive tach. Did the cars with original elctric tachs use a connector at the tach, or were the wires seperate? If they're sepearate, can anyone with a wiring diagram tell me where the wires go?

Thanks
Ken