How I Fixed The Clock In My 77 Corvette

by Jay Ney

Make sure you use care in handling your clock as it would be terrible to damage the hands or the other working parts. 


Grasp the second hand around its round edges and not on the thin needle.

Use a steady upward pull to pull the needle from the clock. Be careful not to squeeze to hard as your fingers might slip and do damage to the needle when the needle comes out. Below is a photo of the needle removed.


Now to remove the minute and hour hand. 
I just used a tiny screwdriver to pry around the round base of each needle.

REMEMBER BE CAREFUL


Now the face can be removed.
Bend the tangs that hold the face to the clockworks. There are three tangs.

One tang looks like the photo below.

There are 2 tangs that look like the one below..

After you have straightened the 3 tangs lift the face off the body.


With the face removed we can see the spots where the tangs for the face were attached. (Marked with red arrows).

The spots marked with blue arrows are case tangs or divots. These need to be bent out of the way so the clockworks can be removed from the case. Once this is done the clockworks pull from the case fairly easily. If you notice from the photo I did not straighten the top case divot because it was not necessary (Yellow Arrow).


Ta Da

Your clockworks are removed.

Earlier, I told you someone put a wind up clock in your Corvette and I know you did not believe me. To the best of my ability I will explain. When you wind a clock you are making tight a spring sometimes called a mainspring. This spring is all the energy a clock needs to work The spring through it's gearing turns a oscillating wheel. This oscillating wheel keeps the time and turns other gears so the hands will move.

Ok so who winds the Corvette clock?

How I Fixed The Clock In My 77 Corvette

Who winds the Corvette clock?

A small electric coil winds the clock. Yes a coil.

The yellow and red arrow point to a pair of contacts. The yellow arrow points to a contact that is attached to the coil. The red arrow points to a contact attached to the mainspring. The blue arrow is pointing to the mainspring gear.

A contact is simply a device that when touched together will allow current to flow.

You can see little nibs protruding from the contacts. These nibs are holding the actual contact on the arm. The contacts are together. Green Arrow!

If power was applied to the clock in the above photo the two contacts (yellow & red arrows) would pop apart. Why? When the contacts are together current flows into the electric coil. When the electric coil is energized the bottom contact pushes up. This action stretches a spring (Mainspring). It is a fast push and enough of one to separate the contacts and then de-energize the coil.

 

The photo below shows the contacts separated..

 

So the clock works like this.

The oscillating wheel oscillates, causing the mainspring to unwind which brings the mainspring contact toward the coil contact. When the 2 contacts meet the coil is energized by 12 volts pushing the pair of contacts up till they separate, re-winding the mainspring and de-energizing the coil. The process repeats as the oscillating wheel oscillates...so on so forth.

I always wondered why the old clocks in cars clicked about once a minute. Now you know. 

(NCRS??) Listen for the click??

FYI. I did a little calculating. The coil in the clock energizes roughly 525000 times a year. 

So now you know how the clock winds.

 

Back to work.

Separate the contacts by pushing up on the contacts where the yellow arrow is shown in the photos above. GENTLY. about 1/8 inch.  

Now if everything was ok with the clock, the oscillating wheel should start to turn. Red arrow below shows the oscillating wheel. The blue arrow points to the outside of the small electric coil.

My wheel did not oscillate. 

Most wind up clocks that don't work that I have taken apart just needed cleaning. 

I blew out the clockworks with canned air. You must be careful not to blow to hard. I suggest you used caned air, not air from a compressor. Air from a compressor might damage the workings because of the velocity. Even canned air might do damage if blown directly at the oscillating wheel so be careful. 

I then got out my safety solve and doused the entire clockworks. 

MAKE SURE that what ever cleaner degreaser you use it is safe for plastics.

I dried the clockworks with canned air. 

I used a fine sandpaper and sanded the contacts. They are pitted bad and black but they cleaned up ok.

I once again doused the clockworks with safety solve and dried it carefully with canned air. 

GUESS WHAT!

The oscillating wheel started turning and before I knew it the contacts were back together. This meant the mainspring unwound and since the clock had no power the oscillating wheel stopped.

When I separated the contacts again the oscillating wheel started turning again. I knew it was fixed. 

Now it was time to put extremely tiny amounts of light machine oil where the shafts ride in the case. I have a syringe with a needle that I have full of machine oil (used it for years). This makes it easy to get to the tight spots.

 I put the unit back in the case and bent the case tangs down. I installed the face then the hands.

My Corvette just came out of the garage after being parked for a few years. It has no battery to test the clock, but wait!; it is a good thing I went to electronics school 22 years ago because I happen to have an adjustable power supply.

I adjusted the power supply to 12V turned off the supply and connected the negative lead to the clock case. I put positive to the terminal coming out of the back of the clock.

 

The moment of truth was when I hit the switch.

CLICK. The coil popped and off it went...

The clock ran flawlessly for 2 days, 2880 clicks of the coil, and I shut it off convinced it will be fine once put back into the car.

I realigned the hour hand as I was sloppy putting it back on the first time. (Just make sure you are exactly on the hour with the hour hand when the minute hand is at 12!).  They are right on now. You might test run your clock connected with jumpers to your Corvette's battery for a day before reinstalling the clock and the center cluster.

Attention

A couple of days after I wrote this article, a member of the
 77 & C3 forum 
posted that after he finished cleaning his clock it worked, but the clock would gain 20 minutes in 30 hours. Ok so this is important information and my oversight. I didn't even think about the clock running fast or slow all I think about is driving the corvette in the summer. Since my center cluster is out of the corvette I decided to take apart the clock to take more pictures so I could share the knowledge with you.
Thanks Bob_77!

OK you will not put your clock back in the case just yet. 

The picture below shows the oscillating wheel spring. (Yellow arrow)
The red arrow points to the oscillating spring tensioner's handle. To adjust the speed of the clock you will move this little handle to the left or to the right. 

SO

You have cleaned and lightly oiled the movement and it is working. The first thing I did was to reattach the face without the movement being in the case. I used tape to hold the face so as not to keep bending the tangs. I added the hands back to the clock putting all the hands at the 12 O Clock position.

Picture shows the face of the clock taped on movement and the connection of the power leads to the clock movement.

I attached a 12 volt source to the clock. Since the movement is not in the case the metal parts are no longer a ground. You must attach your ground supply to the circular spring steel near the positive 12 volt terminal. 

The next thing to do was to get a timing source. IE A watch you can start and stop the second hand on.

I started both time pieces. After an hour I checked it. I found the corvette clock fast.
I turned the power to the corvette clock off so the second hand would stop. I made an adjustment. I looked at the corvette clock it said 12:49 and 45 seconds. I set my watch at 1:00 o'clock and 0 seconds. I turned power back on to the corvette clock and when the corvette clock read 1:00 o'clock and 0 seconds I started the watch. After running on the new adjustment for an hour I found the clock even faster. The adjustments to the lever should be tiny. I started making adjustments to the lever in the opposite direction. 8 adjustments later I decided it was good enough. 

How good is good enough. after letting the clock run 8 hours I found the second hand to be 3 seconds fast. That means every day the clock will gain 9 seconds, about 1 minute in six days or close to an hour in a year. Now that is not to shabby for a 26 year old clock in which the coil had popped millions of times.

SO..

If you have decided to replace your clock and were going to replace the whole movement I suggest doing a cleaning of your old clock before ordering a new one. You might get 10 more years for just a little investment in time. 

Unfortunately I can offer no warranty either express or implied on the information I provided on these web pages. 

I do however claim 2003 all rights reserved. Jay Ney
 

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