VDO clock repaired...almost!!

snowfugger · 11-18-2009, 05:56 PM

So from the great info on this site, I have managed to get my VDO Quartz clock working again. However, a few issues popped up:

1) the clock works when hooked up directly to the battery, but not when installed in the dash, so I'm wondering where the pos/neg wires behind the dash go...

2) when hooked up, the light is always on. What might I have soldered together to make that happen?

What I did to repair it was re-solder the connections that had burnt out, as well as replace the capacitors that had also burnt out. Once I did those two things, the clock started humming away when I hooked it up to the battery, only to re-install and have it light up like a Christmas tree and not work

Thanks in advance

MrScott · 11-18-2009, 06:03 PM

Does the clock work if you turn the lights on? Don't remember if the connections prevent it but is it possible you switched the 'lights' and 'always hot' wire?

snowfugger · 11-18-2009, 07:47 PM

no...it doesn't work, and the dimmer happens in reverse, i.e. if i make the instament panel lights dimmer, it gets a little brightness back, and if i turn them all the way off, it lights up again, but it won't work when connected to the wires coming through the dash.

MrScott · 06:28 AM

There are 3 connections on the back of the clock: always-hot, gound and dimmer. Sounds like you might have the always-hot wire on the light plug and the dimmer wire on the ground plug.

Short version is if it works on the battery but not installed the problem's in the wiring. I'd test the 3 wires with a multi-meter (or consult a wiring diagram if you have one) to confirm which is which.

Edit: Oh and be careful it you're playing with the wires with the battery connected -- if you touch a hot one to the dash you'll either pop a fuse or melt a wire.

snowfugger · 11-19-2009, 07:13 AM

i didn't change the wiring, although i may have soldered something together inadvertantly. I've been looking for a wiring diagram but i can't find one. Thanks for the help though!

snowfugger · 11-19-2009, 08:45 PM

note...lights do not stay on anymore, fixted that, the clock lights works with the rest of the panel, the damn thing just wont run when connected to the wires in the dash. I tried using a wire that had been disconnected still hidden behind the panel, and no dice. That wire may be bad too (hense its lack of use) but for the life of me I don't want to trace this wire all the way back to the battery. I can see where it runs down into the main wire group that goes into the fuse box, but doesn't the hot wire to the clock have to go directly to the battery?

Put another way, what's to stop me from just running another hot wire from the battery to the clock? The dimmer works now, so I don't see why I can't just run it from the battery along with the stereo amp.

Also, fixed the fuel gauge. That was a tough one too, but it works like a charm now. Pulled the sending unit and re-soldered the copper wire to the contact, resoldered a contact on the gauge, and now it's good to go.

Thanks again for the help!

llewellyn56 · 11-26-2009, 10:34 AM

Accordig to the 911 service manual by Bentley, the black wire is the 12 VDC and the brown wire is the ground. You should have the black wire hooked to the middle contact (which is labeled 12 VDC) on your clock. Can't see how the dimmer switch has anything to do with your clock wiring as this is a separate circuit, however the silver housing for the bulb acts a ground for the light.
Check your fuse - you may have blown it by accidently grounding the black wire. It should be #18, and also connects the interior lights. So, if your glove box and dome lights are out, its probably the fuse. I don't recommend connecting straight to the battery. Note if you unintentionally grounded the black wire the fuse has saved you more extensive wiring damage.

llewellyn56 · 11-26-2009, 10:37 AM

PS - I'm referrig to a 1983 911SC.

snowfugger · 12-06-2009, 07:43 PM

Thanks! I got it working about a week and a half ago, but forgot to check the forums for an answer. Funny thing too...you mention the dimmer grounding out, i think that was happening at the same time!

bart1 · 12-07-2009, 05:08 AM

Every post I have read about these clocks is confusing. Maybe this edited pic will help.

Also, does anybody have a pic of the light that goes into the back of the clock. I am doing a project with one and the clock works great, but I can't get illumination to look decent in it. Anybody have a pic of what the available LED upgrade looks like? I mean the bub that goes in...

snowfugger · 12-07-2009, 09:22 AM

it's not a vent...that soldered connetion is what grounds the circuit board to the metal case, and in turn to the ground wire.

bart1 · 12-07-2009, 09:58 AM

Got it, fugger - thanks. I'm sure all of you are impressed with my ninja-like MS Paint skills.

scotricker · 12-07-2009, 12:59 PM

I have been trying to figure out how to get a clock going for awhile now, too.
Which capacitors needed changing? Everthing looks all soldered well.
How do I make it go?

snowfugger · 12-07-2009, 01:24 PM

the bigger white ones...only if they look burned out though. they are like small soda cans, and should be offwhite.

scotricker · 12-09-2009, 05:55 AM

you mean these ones? but they don't look burned out to me..

rick-l · 12-09-2009, 06:19 AM

Is there an integrated circuit in the clock? Can you see the number?
Is that crystal marked 32.768 anywhere?

rick-l · 01:04 PM

How about 4.194304 ?

Does it look like this?

Edit:
Better data sheet link. scroll down and click the PDF symbol by ICM7038
ICM7038 datasheet and Application Note, Data Sheet, Circuit, PDF, Pinout | Datasheet Archive

http://kr.ic-on-line.cn/IOL/datasheet/icm7038_549329.pdf

rick-l · 12-11-2009, 05:48 AM

Come on. I'm dying to find out how they did this. How many electrical parts are in there?

scotricker · 12-11-2009, 12:33 PM

the circuit board is only marked VDO 253 on mine

Billy T · 11-28-2011, 02:15 AM

Thanks for the info and feedback in this forum guys. It helped get mine going!
I had a VDO 253 quartz clock (similar to pic below) die on me for no obvious reason. (1978 vintage)
After checking that the car clock fuse was good I proceeded to strip the dashboard console where the clock sat.
I then confirmed that 12volts was present on the red or +ve clock cable from the dashboard. ("hot" or live cable)
I had no option but to strip the clock.
On opening there was no obvious reason for the clock failure. Internals were clean, gears looked good, meshing and freely turning.
All the gears or flywheels on these clocks are nearly all plastic. At the base of the clock sits a circuit board with a quartz crystal can, 2 capacitors, a resistor, an Integrated Circuit (IC) and the solenoid coil. The solenoid coil generates a collapsing electric field which causes the nearby magnetic rotor armature to rotate.
Thinking the fault may be due to friction, I decided to lubricate all the gears with WD40, powered the clock with 12v, but still no movement. I could see the second hand was 'flicking' on the spot or attempting to move, but didn't have the power to move.
These clocks are generally reliable because of their low component count.
Because I had replacement capacitors and resistors available I decided this was my final shot before I hit the wreckers for spare clocks. (Radio Shack sell capacitors and resistors) I proceeded to unsolder and remove both capacitors and replace them with similar valued ones. These are known as "electrolytic capacitors" and are rated at 16volts and each have a value of 100uF or 100micro Farads. Each capacitor has 2 leads - a +ve and -ve. These leads must be repositioned in the correct polarity on the circuit board. To ensure they are positioned correctly on the circuit board there is a negative or "-" marked on the hole where that negative capacitor lead of each should go.
I did a quick resistance check with my analogue multimeter on the old capacitors I removed and found one to be short circuited. I was now reasonably optimistic of success. The old capacitors I removed were "FRAKO" ones similar in size and colour to the picture on this blog. I proceeded to power up and test the clock again with the 2 new capacitors and bingo, its working like a charm again.
(I did not bother with replacing the resistor)
Reassembled the clock and dashboard and working as fine in car.

I always thought that capacitors were pretty reliable components over time - however their 'electrolyte' - the substance between the +ve and -ve plates can dry up or leak over time, making it fail.

Bill T