Sounds more like an intermittent electrical supply problem. Electronic clock or mechanical? Though if it's electronic, I guess it's possible an electrolytic condenser has gone to condenser heaven.

Your car is at an age where corrosion and/or oxides can really mess with electricals. An easy thing do prior to real diagnosis is to remove the fuse that feeds the clock and replace it with a new one. Remove and replace the new one 4-5 times in rapid succession then wipe its contacts and insert it back in the fuse box. That should clean off the contacts in the fuse box and provide a known good fuse.

 

Does the clock dim with the radio when you turn the lights on as designed?

 

Sounds like someone might've added a clock, perhaps the person who installed the junkyard struts, and didn't get the wiring quite right.

There are four wires to the clock.
A constant 12V+ for memory when the car is off, which sounds like it's a problem in your car.
A ground wire.
A switched 12V+ which provides power only when the key is turned to a powered-up position, which will make the clock display the time.
And a wire from the positive side of the gauge light circuit, which dims the clock slightly when the headlights are turned on. This wire also sounds like a problem.

My '93 didn't have a clock, so I snagged one at the junkyard along with its electrical connector and the four pigtails.
I wired it into my radio wiring, and it worked mint the first time.

I think I figgered out the radio wiring by searching online for a pin-out diagram of 1990s Toyota radios, and then finding the appropriate wires coming from the back of the radio. I probably used my DVOM to verify the wires, but I don't remember because it was well over five years ago.
Maybe I found a pin-out for the clock? Maybe the clock wiring are the same colors as the radio wiring?

 

Bad solder joint.

How to fix your clock on your 2003-2008 Toyota Corolla

Hello ToyotaNation, I know this topic is already a sticky but the person who made the original video I thought did not do a good job. So I made a better one! :grin: I hope this is more helpful than the original video to do this! If you like my video, don't forget to hit the "like" button and...

www.toyotanation.com

 

When I had trouble with my 93 Corolla's digital clock, I pulled it out, took it apart, found the trouble and repaired it. What the problem turned out to be was a combination of bad solder joints on the display vacuum fluorescent tube and bad spring contacts on the connector fingers where the springs press against the pc board contacts.

One Phillips #2 screwdriver takes out the screw holding the clock assembly to the blower vent / radio bezel. Then three #1 Phillips screws hold the clock case assembly together. Carefully lift the two halves of the case apart and don't lose the three clock pushbuttons. Now one #1 Phillips screwdriver takes out the screw on the back of the pc board/connector housing. When seperating the pc board from the connector housing, there are four springs that press against the pc board to make circuit contact. DON'T LOSE THOSE SPRINGS!

The four springs make contact with their mating pc board pads to provide +12vdc igntion switch power, ground, time memory (constant 12 volts), and dashboard light dimmer voltage to dim the clock display when headlights are on. I clean the pc board pads and the pressure finger spring ends so they make good contact with the pc board. I use one of those fiberglass "eraser" pens to clean the contacts, but a pencil eraser or fine Scotchbrite pad would probably work.

The terminals of the vacuum fluorescent display tube will need to be resoldered as shown in my picture. You'll probably find at least a half dozen terminals with cracked solder joints that will need to be resoldered. There is also a single 47 uf @ 16 volts radial electrolytic capacitor on the board. Mine tested good with my capacitor ESR meter so I left it alone. That capacitor should be tested and if bad, replaced with a "low profile" version because there isn't alot of clearance in that case for normal height capacitors.

Now it's ready to reassemble and try it out.

 

Ken, you need to post more often!!!

 

I've been quite busy the past few months repairing/restoring about 65 pinball machines for the recently opened (March 1st) Olympia Pinball Museum. We had only been open two weeks then governor Inslee shut down all entertainment/recreation businesses due to coronavirus. I did a lot of circuit board and connector repairs on those machines. Come next week I will be able to be repairing more of those machines again when some business restrictions get lifted.

 

That's what I'm talking about!

 

Yup, that's pressure finger and contact pad problems on the clock's pc board. An easy fix for you.