My 1992 300E's tachometer does not work. Having searched the archives I see that a likely suspect is the TDC sending unit located on the driver's side in the engine compartment. Where exactly is the unit and what does it look like?

Thanks.

1. Is your clock working? (on the same face).
2. If not check the fuse it supplies the power to both.
3. I know this sounds basic but not sure where you are at technically.

Thai GI sends...

__________________
GI but not GI Joe
They call me "The Thai GI"
Thai in the US Arsenal

Nope, the clock works. I bought the car with a non-running motor (Previous owner's son melted a piston.) My wrench had a '86 300CE engine that I rebuilt and dropped in there. It runs great except for for a cold start idle problem and a dead tach. I've replaced the over voltage relay already.

Any other thoughts?

-Tiberion

I have the same problem (tach and temp gauge won't move, UNLESS...).... I must WHACK the dashboard and then they go up. It seems as though they get a little stuck (only happens in the winter part of the year!)
SImple... give it a try? GOOD LUCK!

__________________
2006 E350 w/ 155k miles (Daily Driver)

Previous:
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)

Nope. All gauges are working only the tach is inop.

I really need to know the location of the TDC sensor.

Look down through the fan and to the right (below the water pump). You will see the sensor attached to a bracket above the damper pulley. It will have a lead attached to it. That's your sensor. However, and I could be wrong, if that item isn't working, your motor would not start, or if it did, your ECM wouldn't be getting good info for spark advance, etc.

__________________
Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.

So, the sensor reads RPM from the dampner. Assuming the car will not run without the sensor then the sensor is ok. And since all other gauges and the cruise control are alive then the problem seems to be either the signal to the tach or the tach itself.

Does anyone know where the tach signal exits the engine bay before I pull the cluster?

Regards, Tiberion

The sensor reads TDC for #1 cylinder. The tach signal is derived from the ECM (I believe). In any case, the easiest approach is to rule out the tach head itself. Pull it and have it tested. I'd bet on that being the source of your problem.

__________________
Jeff Lawrence
1989 300e
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.

Is there a DIY for pulling the cluster for my 300E?

Where do I get a factory service manual for my '92 300E?

There's a good thread in here about removing the instrument cluster...a search on it will bring it up. It also mentions how to make a tool to remove it.

I've had similar problems with gauges on my MBs (esp. fuel gauge) and have found that the cold solder joint in the back of the unit itself is usually a good suspect, esp. when a "tap" on the dashboard seems to fix the problem...

__________________
Chris
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired

"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon

Well, I pulled the instrument cluster today and swapped with a known good cluster. The tach worked. So, swapped in the used tach while mine is being sent off to be repaired.

Thanks to everyone that replied.

-Kevin