HOW-TO: W126 Odometer Repair, Clock Capacitor Replace - Page 3 - PeachParts Mercedes-Benz Forum

steh-fan · #31 11-25-2013, 06:55 PM

Quote:

Originally Posted by JamesDean

I ended up just buying a single 12-tooth drive gear replacement from odometergears.com. It was like $30 all said and done.

Btw, I got mine from this place: Mercedes Odometer gears
$17 for the set of three (and they even had the rare 14/48t in stock which I needed).

JamesDean · #32 11-26-2013, 12:24 AM

Quote:

Originally Posted by steh-fan

I fully agree to that!

I have two quick questions:
1.) What specifications do the capacitors and resistors have (or RadioShack cat #).
2.) I did the capacitor on my watch and it started working again, but it's showing erratic times. I somewhere read a certain resistor needs to be replaced in order to have it showing the right time. Do you by chance know which on that is?

Again, thanks a lot for your help!!!!

The capacitors on the 300SDL's cluster were
220uF/6V
47uF/16V I think.

I replaced them with:
220uF/6.6V
47uF/50V

The resistor was 33 Ohm, which is available at radioshack as that's where I got it. The capacitors are fairly common values so I think RS should have them as well.

Just be sure to open up your speedometer first before buying supplies so you are sure of what you need. The first gen speedometers are different than the second gen. Second gen are what is listed above. First gen I cant recall at the moment.

I've not seen the replacing the resistor comment. I'd have to look at the clock closer and see. As long as you are using the same capacitance on the replacement capacitor I cant see an obvious explanation for the erratic behavior.

steh-fan · #33 11-27-2013, 12:32 AM

Quote:

Originally Posted by JamesDean

The resistor was 33 Ohm, which is available at radioshack as that's where I got it. The capacitors are fairly common values so I think RS should have them as well.

Hi,

very stupid question, but I wanted to double-check before I buy something wrong; I saw that the resistors come in various wattages. Which one would be the best to use? I think RS mainly stocks 1/8, 1/4, and 1/2 Watt resistors.

Thanks a lot for your help!

JamesDean · #34 11-27-2013, 06:19 AM

Not a stupid question at all. I should have specified. The 33 is a 1/2 watt resistor.

steh-fan · #35 12-28-2013, 06:13 AM

Quote:

Originally Posted by JamesDean

Not a stupid question at all. I should have specified. The 33 is a 1/2 watt resistor.

Hi,

I finally came around to work on the odometer gears and the watch.
It was actually quite easy to find the 5 soldering spots to remove the speedometer from the board as someone has done that before (I guess, when they exchanged the speedometer with an US version).

I realized that the capacitors and also the board layout look very different from yours. I only had one 47uF and one 220 uF and both looked very modern. I thought it wouldn't make sense to replace them as they still looked fine.

As for the watch, I have a 200ohm resistor around which it looked pretty black. However, I could test it and so I assumed it must be ok.

What is your opinion on replacing these resistors and capacitors?

Thanks!

JamesDean · #36 12-28-2013, 04:23 PM

Quote:

Originally Posted by steh-fan

Hi,

I finally came around to work on the odometer gears and the watch.
It was actually quite easy to find the 5 soldering spots to remove the speedometer from the board as someone has done that before (I guess, when they exchanged the speedometer with an US version).

I realized that the capacitors and also the board layout look very different from yours. I only had one 47uF and one 220 uF and both looked very modern. I thought it wouldn't make sense to replace them as they still looked fine.

As for the watch, I have a 200ohm resistor around which it looked pretty black. However, I could test it and so I assumed it must be ok.

What is your opinion on replacing these resistors and capacitors?

Thanks!

I would replace those capacitors for certain. The one says W. Germany on the side of it, I believe which puts it at the minimum of 20 some years.

If the resistor(s) don't look damaged or harmed in any way I would not bother replacing them. The capacitors are what can age and fail.

steh-fan · #37 12-29-2013, 06:38 AM

Quote:

Originally Posted by JamesDean

I would replace those capacitors for certain. The one says W. Germany on the side of it, I believe which puts it at the minimum of 20 some years.

If the resistor(s) don't look damaged or harmed in any way I would not bother replacing them. The capacitors are what can age and fail.

Thanks for the recommendation!!
The next time I'll have to work on the odometer, I'll replace those.

So now my watch is finally keeping the right time!!!
I had most of the connections re-soldered together with lubing both the gears and adjusting mechanism seems to have helped...

Very happy and thanks for all your help!

steh-fan · #38 01-02-2014, 02:50 AM

Quote:

Originally Posted by JamesDean

I would replace those capacitors for certain. The one says W. Germany on the side of it, I believe which puts it at the minimum of 20 some years.

The capacitors are what can age and fail.

I can't believe it!
I was so happy that the clock is finally working accurately, but now I realized that my speedometer is about 10-15 mph too fast (depending on the speed).

Could this be in connection to the old capacitors? Or what else could it be?
I replaced the gears (but miles are correct as tested with GPS) and soldered the connections to get the speedo-/odometer off the board.

Thanks for your continued help!

pmckechnie · #39 01-02-2014, 09:31 AM

Step-fan,
I was thinking about your 10-15mph error and was going to try to help, but I realized I didn't know what kind of car you have. I tried to fine that information in your previous post but couldn't find anything. So I'm sorry, I can't help. I gave some advice one time when I didn't know the exact car and was wrong. I gave bad advice which was completely wrong. And as we know wrong advice is a bad thing.

Paul

JamesDean · #40 01-02-2014, 09:46 AM

Quote:

Originally Posted by steh-fan

I can't believe it!
I was so happy that the clock is finally working accurately, but now I realized that my speedometer is about 10-15 mph too fast (depending on the speed).

Could this be in connection to the old capacitors? Or what else could it be?
I replaced the gears (but miles are correct as tested with GPS) and soldered the connections to get the speedo-/odometer off the board.

Thanks for your continued help!

If the miles are correct we can conclude the speed signal is correct and the problem lies in the circuit that controls the speedometer needle. I would start by replacing the caps. They might not be providing enough power to drive the little motor that runs the speedo needle. I'd also reflow all the solder joints on that board as well. There are not a huge amount so it should be fairly straight forward.

steh-fan · #41 01-02-2014, 02:10 PM

Quote:

Originally Posted by pmckechnie

Stefan,
I was thinking about your 10-15mph error and was going to try to help, but I realized I didn't know what kind of car you have. I tried to fine that information in your previous post but couldn't find anything. So I'm sorry, I can't help. I gave some advice one time when I didn't know the exact car and was wrong. I gave bad advice which was completely wrong. And as we know wrong advice is a bad thing.

Paul

Hi Paul,

thanks a lot for trying! I greatly appreciate your efforts and fully understand your concerns about wrong information given. However, I personally think every reader should be able to judge whether that particular advise applies to their cars and should never taken any advise as guaranteed as every situation is different. I have been given 'wrong' information before, but there's nobody else to blame besides me as it was my very own decision to follow the advise.
That's part of the risk you're accepting using an online forum, and if I wasn't accepting that risk, I simply have to bring the car in.

Anyways, my car is a 1989 300SE EURO with ASD and France-specific rear diff ratio of 3.07.

I hope that helps.

Thanks,
Stefan

steh-fan · #42 01-02-2014, 02:12 PM

Quote:

Originally Posted by JamesDean

If the miles are correct we can conclude the speed signal is correct and the problem lies in the circuit that controls the speedometer needle. I would start by replacing the caps. They might not be providing enough power to drive the little motor that runs the speedo needle. I'd also reflow all the solder joints on that board as well. There are not a huge amount so it should be fairly straight forward.

Thanks!
I was thinking the same, and I will report back whether that helped.

JamesDean · #43 01-02-2014, 02:14 PM

Has the speedometer pod/cluster ever been changed out with a different unit?

The US 300SE was 3.46 gear ratio evidently..

1989-1991, 300 SE, M103.981 3.0L I6, 3.46 1 Liter

If someone swapped in a US speedometer cluster than that would explain your speed difference.

steh-fan · #44 01-02-2014, 02:24 PM

Quote:

Originally Posted by JamesDean

Has the speedometer pod/cluster ever been changed out with a different unit?

The US 300SE was 3.46 gear ratio evidently..

1989-1991, 300 SE, M103.981 3.0L I6, 3.46 1 Liter

If someone swapped in a US speedometer cluster than that would explain your speed difference.

Hi,

the car was brought to the US in 1999 and yes, they federalized it and swopped the speedometers. That's why I mentioned above that I could easily detect the solder points for removing the speedometer since it has been replaced during the federalization process.

However, it was working correctly until last weekend when I swopped the gears and soldered the speedometer to access the gears.

So something most have gone wrong during that process...

Is there a way of adjusting an US speedometer for the different ratio?
Maybe I was soldering something that was inactivated before....?

JamesDean · #45 01-02-2014, 02:30 PM

I dont think the speedometer head would vary from US to EURO. I think the drive circuitry would change based on diff ratio (at least thats how I would have done it) and since you said it was ok before the change we can assume that the head is Ok and correct.

There are only three or four solder points so thats a low probability of fouling up.

I would replace the capacitors and see what that does. Perhaps the new gears added additional drag on the motor causing it to require more torque/current from the capacitors and if they were marginal to begin with the additional load might make them slow down..

Maybe. Just speculating.