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Old 03-02-2007, 10:18 AM
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Join Date: Nov 2004
Location: Austin, TX - Hook 'Em
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How can I test my clock, gauges, etc on the bench? 1980 450sl

Good morning!

I started this whole project with my clock that wasn't working. I took it out and replaced the resistors, and I finally got the IP back in the car yesterday to test. Well, I could hear the clock ticking, but the arms weren't moving. To figure out what's wrong I'd like to be able to power the clock from my bench so I can check out what the gears are doing, etc.

1) Is there a way to test the clock, and any other gauges or IP lights while the whole IP is still on my bench?

2) Does anyone have any idea of what may be wrong with the clock?

Thanks!!

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Old 03-02-2007, 10:14 PM
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Join Date: Apr 2004
Location: KY USA
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I think but am not certain that 1980 had the clock in the tach pod, and this is what I am familiar with.

You do mean the capacitors, right? Are they the right value? Are they in with the correct polarity? You can hook up the clock (only) to a 9 volt transistor radio battery - OBSERVE THE CORRECT POLARITY!!!!- and put +9 to the tab that sticks out of the clock. This is isolated from the entire rest of the panel, you won't power any other gauges. Attach the ground (-) to just about anywhere else on the frame of the gauge (the spot that you hopefully resoldered at the back of the clock to the gauge frame would be fine). It should tick, and the hands will move -but be patient, it's hard to see, sort of like watching water come to boil. I know from fixing several of these that 9 volts from that particular type of battery will be enough to make it work.

I don't see how you could put the hands on so that they would hold on to the shafts but not actually move; if they don't move, there may be something other than the capacitors wrong with the clock.

I repaired 6 out of 7 clocks by just changing the caps. The seventh had damaged gears in the adjuster.

BTW, if you reversed the polarity on one or both caps, the clock might tick but not have enough power to move.
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Last edited by Strife; 03-02-2007 at 10:24 PM.
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Old 03-02-2007, 10:19 PM
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P.S. to the previous post:

Do NOT test any of the other gauges by applying voltage to them. They work on current (the fuel and temp gauges) and applying more than a certain number of milliamps of current through them not via the resistor in the temp sensor or fuel pot will probably damage them. I know of no "spec" to test them with.

The tach works on pulses and the same caution as above applies.

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86 560SL
With homebrew first gear start!
85 380SL
Daily Driver Project

http://juliepalooza.8m.com/sl/mercedes.htm
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