[W126 Coupe] electrical expertise needed

[Markus Meyer]

 An update on my intermittent working clock issue.  I took the clock out and attached it to a free standing 12 volt battery from my alarm system, as well as the car battery.  Didn't change a thing.  Everything else checked out okay, so I UPSed it off to The Benz Store, and a few days later I got a box back with a unit that I plugged in, and since Monday night, has been working non-stop.  Not sure what they changed or fixed or updated, but all I know is I have a non-intermittent working clock again (knock on wood!).  Thanks to Dick for the suggestion on using them.  Chet - if you are out there, I still have a spare I picked up on ebay from an 89, and you are correct, it only has 1 capacitor as opposed to my 87 with 2.  Anyhow, next time we get together maybe you can show me how to swap the capacitor on that unit to see if it will also start working regularly again. Thanks to all who offered help and suggestions.Markus--- On Wed 09/14, a figment of the imagination < 
figstir at yahoo.com > wrote:From: a figment of the imagination [mailto: figstir at yahoo.com]To: mfmeyer at iwon.comDate: Wed, 14 Sep 2005 09:31:58 -0700 (PDT)Subject: Re: [W126 Coupe] electrical expertise neededHey Markus,It sounds like a voltage problem right off the bat.Dick's suggestions can be confirmed by myself, aswell.I would like to add the following.1. The terminal off the back of the instrument clusterbehind the tach is attached to a reddish wire whichprovides 12-volts. Test this wire to make sure youare getting the proper voltage; it should be around 12volts, although the clock should probably be able towork with as low as 9-volts. 2. If the voltage is low, then you have other obviousissues, with regards to the battery, alternator, orother.3. With the clock and/or instrument cluster off thecar, simply connect 12-volts directly to this samelead from a separate 12-volt source. Use the negativeterminal as your ground; you should be able to findthe common terminal to the 
clock easily on the clockitself or on the back of the instrument cluster. I amsure that this is what you were thinking and wereasking about.My only concern here is that you make sure you areconnecting directly to the clock. There are indeedcapacitors, IC chips, transistors, and resistors inthe back of the instrument cluster that could bedamaged, by accident, if the are connected to 12-voltsdirectly when they were not designed to be. Theterminal mentioned in #1 should be fine but check itjust in case.4. Your ground on your instrument cluster could befaulty. While for me the jury is still out, I amaware of others with SEC's having problems with faultygrounding on their instrument cluster. I currentlyhave possibly a faulty ground to my instrument lights,causing them to fail. My comment about a faultyground is that, if this was indeed the problem, thenyou should see other problems with other electronics. 5. Based on this logic in #4, which may not be fullycomplete, I would 
suggest that you may not have theproper voltage being sent to the clock. As stated in#1, check it. Check the battery level, check thealternator, check for other problems with otherdevices or shorts. 6. In general, a faulty capacitor should have nothingto do with intermittent operation of your clock. Acapacitor merely stores a set amount of voltage, afterbeing in properly adjusted with resistors and otherelements. You seem to be describing a run-down typeof phenomenon, kinda like a "subclavian steal" inmedicine or even "sun-downing" in psych, or somebetter analogy. [Hence, alternator, battery, etc..issues]. I highly doubt a faulty capacitor would allowfor intermittent operation, but a faulty andnon-constant voltage supply would.I'm sure your clock is good! You may need to takecare of a loose connection somewhere. You can checkcontinuity and resolder broken or faulty leads orterminals. Make sure you check voltage, as Imentioned in #1. Another analogy is your analog clockin your
  
home/work, which slowly runs down or stopsworking as the AA battery dies off. If you aredraining the battery as you go throughout the day,your clock will be affected. If this is indeed thecause, how this drain is occuring needs to beinvestigated.7. Regarding a good direct grounding point, Irecommend the common ground source behind theinstrument cluster. There are at least 3 big boltsholding down the terminals of numerous brown leads.If this is helpful, that's great. If not, keep tryingwith these and others' suggestions. I am certain itis very simple. Please keep me informed.Cheers!-fig__________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com

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