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You need to diagnose the cause of no lights rather than to replace parts. Voltage needs to be checked. Grounds need to be checked. Very rare for ALL of the bulbs not to work unless it's a wiring problem. On the tach, did you verify that the drive was good and that the cable was good before replacing the unit?
If the bulbs are getting twelve volts, you obviously have a grounding issue which seems the most probable to me. Not a lot to go with on the tach (distributor or generator driven). You are either going to have a broken cable/drive gear or a bad tach? If you find your cable is working perfectly and you get no reading on your tach, then I would say the tach speedcup and needle stem have separated which means your needle will not move...a tach that needs to be repaired.
If I wasn't clear, you need to know if it is your tach side forward or your cable side back. Again, if your cable is not broken and your distributor drive gear or generator drive gears are working perfectly, then the problem most likely has to be on the tach side. And with a working cable, I cannot think of anything else that would cause no needle movement except internal stem/speedcup problems. Now, if you have the same problem with the old tach and now a "Brand New Tach", I would be making double sure that the cable side is not the fault.
Last edited by tgtexas02; Feb 5, 2020 at 06:55 PM.
You need to diagnose the cause of no lights rather than to replace parts. Voltage needs to be checked. Grounds need to be checked. Very rare for ALL of the bulbs not to work unless it's a wiring problem. On the tach, did you verify that the drive was good and that the cable was good before replacing the unit?
Thanks for the tips. I'm not a mechanic but will try to figure out how voltage is checked and which grounds to check. Tach is brand new and cable as well. Bought the tach from Corvette Central.....don't know if they checked it before mailing to me. It's a generator driven tach. Thanks for your help.
You have to get the connector on the back of the tach housing on good and tight or the cable inside the sheath won't seat....the tach gear housing on the back of the generator may have a plastic nylon gear inside that can get stripped; its easy to take the cover off and examine that.
Thanks for the tips. I'll check the grounds. Tach is brand new and cable as well. I assume Corvette Central checked the tach before mailing it to me. It's a generator driven tach. Appreciate your help.
Make sure your dimmer switch is rotated counter-clockwise on the headlight switch. Then make sure you have 12 volts coming out of the switch on the dash light wire.
Good point about the dimmer switch!!! I'll also add, that with this little bit of additional information, the NEXT thing I would check is the output drive off of the generator. See if it is turning when the engine is running.
Welcome to the forum.. How about some pics of your white '61 and some back-story??? :-)
You can disconnect the cable at the back of the generator and use a drill to spin the cable.. have a friend look at the tach to see if it's registering while you spin it.
It's been a while but I BELIEVE you need to reverse the drill direction to do this.
All due respect, I would strongly advise NOT to hook a drill to the cable to test the tach if you don't know which way the rotation goes. What needs to be verified is power TO the tach....and that is done by inspecting the generator drive, not by-passing it.
All due respect, I would strongly advise NOT to hook a drill to the cable to test the tach if you don't know which way the rotation goes. What needs to be verified is power TO the tach....and that is done by inspecting the generator drive, not by-passing it.
Point taken.. You prob should confirm the direction before connecting a power tool.... You can flick it with your fingers while someone watches the gauge to confirm the direction.
Guess it could be argued but I don't think using a drill would cause any damage if you carefully attach and use slow or moderate speeds. The correct direction is using the drill in reverse to move the needle for readings. Running the drill in the opposite direction causes the needle to stay pegged on "zero" as internally it has a stop tang to prevent backward movements of the needle...works exactly like the speedometer needle when driving the car in reverse. The tach and speedo internal mechanisms are for all intents and purposes identical mechanism. Following is what I would do:
--Disconnect cable at rear of generator and with a drill run in reverse direction and see if tach needle registers.
--If needle registers the tach is properly working so check generator tach drive gears by removing rear cover. Vendors sell replacement gears if broken/worn/missing teeth.
--Or, if no tach needle movement, insure that the cable is fully seated and the coupling is properly threaded and tightened on the rear of the tach unit and repeat check with drill in reverse. If still no tach needle movement, remove tach unit and with your fingers spin the rear tach shaft in a counter-clockwise direction. You should see at least a 500 to 1500 RPM deflection of the tach needle and this would indicate the tach is functioning properly. No needle movement, contact the vendor you purchased it from.
As a pro, I would start with checking the generator drive first. Why? Because it requires no tools, it only takes a minute, and the tach is new. And the old tach had the same problem. Why get out the drill and risk breaking the new tach BEFORE you even check the drive system?
As a pro, I would start with checking the generator drive first.
What happens when you get a screwdriver, remove the tach drive cover, look at the gears, and everything looks good? What would be the next step? We are all just trying to help the original poster definitively isolate his problem in a methodical way and fix the issue. I think it is equally simple to remove the cover or use the drill whatever works for the poster who is not a Pro. As far as damaging the tach, the thing was designed to run at thousands of RPM's for long periods of time so running for a few seconds using a drill instead of a generator...hopefully enough info has been provided to resolve his problem. I do not want to complicate things by trying to help.
The tach output drive at the generator can be looked at visually to see if it's turning when the generator is. Simple. Or if the cable is out, see if the cable spins. Easy.
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White 61 vette
