bench test clock

by jpowen49 Thu Sep 05, 2024 11:27 am

Can I bench test this clock without burning it up. TIA.

by zucchi Fri Sep 06, 2024 8:43 am

Talk about serendipity; Just last weekend, I swapped the clock in my Monte Carlo with one of the rebuilt clocks I have on my shelf.

The answer to your question is "Yes" but it's better if you open it up so you can see if the solenoid is fried. Even if it's not fried, it may not work for various other reasons.

If you're squeamish or reluctant to open the clock, do a rudimentary continuity test across the two terminals using a meter, NOT a 12V light.
If there's no continuity, there are two reasons; the solenoid is fried (most likely), the mechanism is dirty and needs service.
If there is continuity then using a 12V power source, attach ground "-" to one terminal then momentarily touch the positive "+" to the other terminal. You should see a spark and hear a light "thud" as the solenoid engages to wind the spring. If you don't hear a "thud", DO NOT try to energize the solenoid again, prepare yourself to open the clock.
If it made the "thud" sound and everything is ok, the clock should start ticking. If it doesn't, test for continuity again. If the meter shows the circuit is closed, you'll need to open the clock. If the circuit is open, try twisting the clock. What that means is grasp the clock in your hand like you would a door knob then quickly twist your hand/wrist, like you would a door knob, back and forth a couple of times. That helps the flywheel inside the clock to get started turning. If it doesn't start working after that, you'll need to open the clock.

by Mcarlo77 Fri Sep 06, 2024 9:15 pm

I've opened up several dozen of these...no big deal. Remove the hands by lifting straight up. Then, straighten the tabs on the clock face so it can be lifted exposing several crimped tabs (you can see one of them below the adjuster knob in your photo). Straighten those and lift the inner works out of the shell. If that clock hasn't run in a long while, I doubt it will start when putting voltage to it. And yes, you can hook 12V to it without any problem. So, as Zucchi mentioned, first thing to do after opening it up is to look at the coils. It will be obvious if they are burnt. Can also look closely to see if one of the wires coming off the coils is broken. Either one is a sign it's shot.
If both look good, squirt a little light machine oil (do not recommend using WD40; although for testing purposes, it works fine) on the gears, manually wind the mechanism and give the little flywheel a flick and see if it continues to unwind on it's own. May take a couple of tries to get all the parts loosened up. Lastly, put power to it and see if it works on it's own. If so, put it all back together and should be fine for a year or two before it needs to be lubed again.

P.S. Little known fact, the coils can be replaced/swapped if done carefully...and, if you can find a good replacement. I just refurbished a clock for my Monte using the coil from a NOS Chevelle clock. Found the clock on e-Bay for less than $30 earlier this year.

by zucchi Sat Sep 07, 2024 6:40 pm

I just finished recording a video on this topic. I expect to publish it on YouTube this coming Monday.

by jpowen49 Sun Sep 08, 2024 8:36 am

Thank you both zucchi and Mcarlo77 for taking the time to help me. I followed your instructions and was successful in getting the clock running, thank you so much.
No continuity so I opened it up as instructed. The coils looked good but the points were stuck open. I sprayed the works with electrical contact cleaner and the points closed on there on. I checked for continuity again and it was good so I connected it to a battery. To my surprise it started running. Very Happy

A few pictures for anyone who hasn`t opened one up. zucchi can you post a link to your YouTube channel. Thank you both again.

by jpowen49 Sun Sep 08, 2024 9:37 am

Back together letting it run for awhile.

by 76 Malibu Sun Sep 08, 2024 1:10 pm

Thanks for the info in this thread. Does the larger clock used on the horizontal speedometer dash use the same internals as this clock? I bought a used clock and it doesn't work. A few restoration shops said they won't restore that type of clock, so maybe I will try to do it myself. It doesn't look too bad.

by zucchi Mon Sep 09, 2024 12:48 pm

Here's the video:

jpowen49 wrote:zucchi can you post a link to your YouTube channel.

Certainly: https://www.youtube.com/channel/UC-q-c4ylQUn6PXiQu9HZiOQ/
It's also in my signature as "Drive your old car forever" Smile

by 76 Malibu Mon Sep 09, 2024 3:44 pm

zucchi wrote:Here's the video:

jpowen49 wrote:zucchi can you post a link to your YouTube channel.
Certainly: https://www.youtube.com/channel/UC-q-c4ylQUn6PXiQu9HZiOQ/
It's also in my signature as "Drive your old car forever"

Do you know if the workings of the larger clock used on Malibus with the horizontal speedometer dash will be the same as this round dash clock? I'd like to work on mine, but not sure if it is a complete different design or not.

by zucchi Mon Sep 09, 2024 4:07 pm

76 Malibu wrote:Do you know if the workings of the larger clock used on Malibus with the horizontal speedometer dash will be the same as this round dash clock?

GM used two manufacturers during the 1970s; Borg Instruments and Westclox, a.k.a. General Time or G.T. Corp.; your clock will be one of these.

The clock assemblies are interchangeable but their internal parts are not. The G.T. Corp. clocks feature a dual wound solenoid whereas he Borg clocks have a single wound solenoid. The clock in the video is a G.T. Corp clock. The link below goes to an article about repairing a Borg clock: https://www.oldcarsweekly.com/features/putting-the-ticktock-back-in-your-old-car-clock-rehab

by 76 Malibu Mon Sep 09, 2024 4:14 pm

I just pull my clock off the shelf, it says GT corp on it. Thanks, it sounds like I got a new project to work on.

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