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Discussion Starter · #1 ·
I'm hoping someone knows how to rid my car of this voodoo.

I'm driving the car and depress the brake pedal, and the clock stops, then goes backwards for a couple of seconds, then resumes its normal course. The clock also reacts this way if I open the car door(s).

Whatcha think? :1zhelp:
 

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I'm hoping someone knows how to rid my car of this voodoo.

I'm driving the car and depress the brake pedal, and the clock stops, then goes backwards for a couple of seconds, then resumes its normal course. The clock also reacts this way if I open the car door(s).

Whatcha think? :1zhelp:

My first thought was it's time for you to enroll in a Looney-Tunes farm.

Does your clock do this ONLY when your engine is running or will it also do it when the engine is shut off? My thought is the diode trio in your alternator is failing and the alternator is occasionally going into reverse polarity. Is your alternator the original 10-DN that uses an external voltage regulator or has it been changed to the later 10-SI with the internal voltage regulator?

The original clocks were the "old style" that used a mainspring and an electromagnet to rewind them every minute (the CLICK you heard every minute). If it's the original clock with the original guts it would be impossible for it to run backwards. But if it has been changed over to a quartz powered movement I would think it's possible to run backwards IF the polarity got reversed.

Didn't you e-mail me once about your amp gauge being stuck? And by zapping it with a straight 12 volts it started working again? Have you made any changes to the wiring going to your amp gauge?
 

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Discussion Starter · #3 ·
Thanks a lot for the reply. I think you nailed it.

My first thought was it's time for you to enroll in a Looney-Tunes farm.

Does your clock do this ONLY when your engine is running or will it also do it when the engine is shut off?

Yes, ONLY when the engine is running.

My thought is the diode trio in your alternator is failing and the alternator is occasionally going into reverse polarity.

Can that be tested to be sure?

Is your alternator the original 10-DN that uses an external voltage regulator or has it been changed to the later 10-SI with the internal voltage regulator?

It's the original alternator with the external voltage regulator.

The original clocks were the "old style" that used a mainspring and an electromagnet to rewind them every minute (the CLICK you heard every minute). If it's the original clock with the original guts it would be impossible for it to run backwards. But if it has been changed over to a quartz powered movement I would think it's possible to run backwards IF the polarity got reversed.

I wasn't sure if the clock was changed over to Quartz, but from your explanation I would think it has. The second hand "sweeps" around the dial, not click with each second. I thought the Quartz movements clicked and didn't sweep.

Didn't you e-mail me once about your amp gauge being stuck? And by zapping it with a straight 12 volts it started working again? Have you made any changes to the wiring going to your amp gauge?

Yes I did, and I haven't made any wire changes since.
 

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Thanks a lot for the reply. I think you nailed it.

Okay, I did some research on the old external regulated 10-DN alternators and see they have 3 positive and 3 negative diodes; not a diode "trio" as I had assumed (my 67 year old brain is failing).

The 6 diodes can easily be tested with a common battery-powered test light. Connect the test light to the diode and current should only flow thru it in one direction but not in the other direction. So 3 of your diodes should pass current in one direction and the other 3 in the other direction ONLY. If the test light passes current in both directions the diode has failed

The diodes in your alternator are pressed in with a light press fit and over time vibration can loosen them so they quit uh "dioding". If you find any that have loosened you can gently peen the edges of the hole they go in and use red Loctite to secure them. Or you can buy a 10-DN rebuild kit over the internet that includes all of the parts needed to freshen it up (new front and rear bearings, brush holder, diodes) for not much money.

The quarts clocks have a continuous motion second hand (it "sweeps") so if yours sweeps it has been updated to the more efficient quartz style that does not reset itself with an electromagnet CLICK every minute.

As DC motors will run backward if the polarity is reversed I can't help but suspect your alternator is the cause. The external voltage regulator's innards is grounded to it's outards (is that a word?) via a small braided ground wire connected to it's base plate because the two parts have rubber in between to dampen vibration. So use your test light to see if the cover is grounded.

If your '66 isn't 100% original and you don't mind updating it I would suggest switching over to the later (and MUCH better) 10-SI alternator. The "SI" stands for Systems Integrated (internal regulator) and the most common used is the 61 amp version.

Feel free to contact me anytime at [email protected]
 

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Discussion Starter · #6 · (Edited)
Thanks, toobroke - I'll be looking into alternators, but in the meantime may I ask ... when the polarity is reversed- however temporary due to the bad diode, I imagine that reverses the polarity on ALL electrical parts of the car, and can that reverse polarity damage anything?

What's your thought on the rebuild kit? My alternator (and the rest of the car) is pretty much all original, so I would want to keep it that way until I have no choice.

Whatcha think of this ...
http://www.ebay.com/itm/10DN-Delco-alternator-repair-kit-63-to-72-Chevy-Chevelle-Camaro-truck-Corvette-/201052116364?pt=Motors_Car_Truck_Parts_Accessories&hash=item2ecfa3d58c&vxp=mtr
 

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Thanks, toobroke - I'll be looking into alternators, but in the meantime may I ask ... when the polarity is reversed- however temporary due to the bad diode, I imagine that reverses the polarity on ALL electrical parts of the car, and can that reverse polarity damage anything?

What's your thought on the rebuild kit? My alternator (and the rest of the car) is pretty much all original, so I would want to keep it that way until I have no choice.

Whatcha think of this ...
http://www.ebay.com/itm/10DN-Delco-...Parts_Accessories&hash=item2ecfa3d58c&vxp=mtr

Yes, I would buy that rebuild kit in a heartbeat as $25 is dirt cheap. Do you have a soldering iron or soldering gun (like a 200-250 watt Weller)? The pigtails of the 6 diodes will have to be soldered with thin rosin-core solder (available from Radio Shack for about $7).

To get the rear bearing out easily heat the boss around the bearing with a propane torch for a minute and the bearing will almost fall out from gravity alone. To install the rear bearing lube the bore with grease then use a flat steel plate or thick steel washer against the bearing and press (best way) or hammer it in from the inside toward the rear until it's flush. And add a little bit of chassis grease to the bearing.

The front 203-FF bearing is probably made in China so I'd strongly advise you to carefully pry either (or both) of the seals out and pack it completely full with any stiff grease before installing it. You can use an o-ring pick to remove the seal; picking at the OUTER edge until it pops out. I have seen some of these Chinese 203-FF bearings with no grease in them so it's always best to hand pack them completely full and any excess grease will just get pushed out thru the seals
 

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Discussion Starter · #8 ·
Okay then, I think I'm on my way.
I'll let you know how it all turns out once I get to it.
Thanks a lot for the guidance. :cheers:
 

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Discussion Starter · #9 ·
Here's one for the WTF book ...

The plug for the ammeter wasn't plugged in. I plugged it in, started the car, depressed the brake pedal, and the clock kept on sweeping correctly.

How 'bout that.
 

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Here's one for the WTF book ...

The plug for the ammeter wasn't plugged in. I plugged it in, started the car, depressed the brake pedal, and the clock kept on sweeping correctly.

How 'bout that.
Not really surprised .I was gonna say something about the ground being switched somehow but ended up just watching how this played out. I guess I should have posted......it made more sense to me than the alternator theory since it only happened when you stepped on the brake pedal.
 
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