Installing tachometer

[116.025]

Two questions

What's this one from?

I wish I knew...I don't think I've seen one from a 116 with the redline past 6500rpms (as in the case of my 280SE and 280SEL)

Secondly, does the oil pressure line simply unscrew from behind the cluster?

Yes, it's a 10mm or 9mm nut that screws into the oil pressure gauge.  You'll want to lean it out on the trio gauge side, since the oil line is the shortest leash (by a fair bit).

Chaz, I don't know the answer to your question for certain, but based on Big R (or AYOMEA)'s post in another thread, it seems logical, and also based on BAR's post in this thread.

[koan]

In 116 and 107 vintage cars it is gearing within the speedometer that compensates for rea rend ratio and tyre size variations, you will need to use your original speedo.

k

[oscar]

Chaz, sorry I thought you did do the install.  Nonetheless from what everyone has said before me and in my "faulty tacho" thread I'll quote BigR

tacho's on a *petrol car* ain't rocket science - it counts ignition pulses to the coil and depending on how many cylinders the engine has, which is preset in the tacho, it calculates the RPM to display, IE on V8, there are 4 ignition pulses per revolution, 3 in a 6 cylinder and 2 in a 4 cylinder. So on a V8, it counts 4 pulses as 1 revolution, obviously the faster the engines turning the closer the pulses are together. Dead simple really.

So definitely yes, you'll need a tacho to read a 6 cylinder. 

Koan, I think you're right too and I'm wondering whether you're referring to a mention somewhere I made about my V8 350 speedo has a 107 part numbert on the faceplate.  Looking at "s class" cluster pics, his are either 110 or 116 I can't make it out.  I haven't looked hard enough or can't make out any 450 or 6.9 part numbers on speedos. I'm assuming though the 107 and 116 share the same ratios.

The tacho part number isn't visible on the front unfortunately but based on the redline, a 6.9 start's at about <5500rpm I'd assume a 450 is between that and my 350 at 6250rpm approx, a 280 seems to be 6500rpm.  It seems the bigger the engine, the lower the rpm.  Maybe the one I pictured is for an early 280S though early clocks have minute markings not 5 min markings (A big, I ThinK ).   Plus Dudu's I haven't seen before and the ebay tacho is different again.

Gee, There's so many variants, there's probably other issues like d-jet, k-jet, emissions that changed how rpm recomendations changed.  Anyway, Chad, thanks heaps for the tips, again.   

So if anyone's after a 8-cyl tach, here's the german ebay link. I think I'll just pull mine out and have a go fixing it and report back in tears

[Papalangi]

I think I'll just pull mine out and have a go fixing it and report back in tears

Oscar,

There is a good chance you have bad solder joints and/or bad electrolytic capacitors.  The tachometer is essentially an averaging voltmeter and uses a small IC and a handful of discreet components.  What usually fails is the electrolytic capacitors due to heat, vibration and age.  If your clock doesn't work also, it is probably due to the caps.  When you have it out on the bench, look for small gold(?) cans on the clock board.  If you can see any rubber or the leads themselves, they need to be replaced.

You might try a search on repairing the clock here or at the forums at mercedesshop.com

Michael

PS, the armature and coils are very fragile, be very careful while tinkering.  IIRC, there may be an adjustment pot to trim the tach if it seems out of adjustment. 

[oscar]

Thanks papalangi,

The merc shop site led me to other sites and as far as fixing the clock (which mine doesn't work) I found a few sites:

http://www.drivewerks.com/tech/mult_vdo_clock_repair.htmPorsche enthusiasts to the rescue again
http://articles.mbz.org/instrument/renew/Gold caps pictured.

Thanks for the heads up on what to expect in the tacho.

Bloody wedding anniversary tomorrow, so there'll be no progress for a few days.
Cheers, Simon.

[Papalangi]

You are welcome Oscar,

The MBZ.org article mentions that you need to check for polarity on the caps.  I don't think it makes the point strongly enough.

If you get the polarity wrong, the caps WILL EXPLODE.

Usually just a bang and a whiff of smoke but not something you need to have happen just as you are patting yourself on the back for a job well done.

Michael

[WGB]

My UK originating 450SEL has a Tach which is redlined at 5,800 rpm.

I have used the previous articles to repair my clock (Which has been running flawlessly for 18 months after replacing the capacitances), repair the odometer and repaint the instrument needles.

The capacitances were not a standard item at Dick Smiths but the correct ones were in a pack of mixed capacitances that the store sold for about $6.

The other great improvement was to replace the speedo cable and get rid of the bouncing speedo needle at low speed.

Even with buying the cable from the local agent the whole Instrument refurbishment came to about AUD$ 80 and greatly added to the enjoyment of the car.

Bill

[116.025]

Gee, There's so many variants, there's probably other issues like d-jet, k-jet, emissions that changed how rpm recomendations changed.  Anyway, Chad, thanks heaps for the tips, again.   

I think I'll just pull mine out and have a go fixing it and report back in tears

Anytime, Oscar.  Glad to help.  Also glad you hunted up Big R's tach stuff, since I was in a lazy mood at the time and didn't. 

Haha, I hope you report back with a functioning tach!  They're great fun.

[koan]

Couldn't find your post oscar about the V8 350 speedo starting with a 107 number. 6.9 speedos are 116 542 34 01, calibrated to 260 kmh, change points I 104, II 170.

I got a cheap cluster on e-bay sometime ago, speedo is 107 542 31 01, calibrated to 240 kmh, with change points marked  I 52, II 87, III 145.

Anyone know what it came out of?

k

[oscar]

Hi Koan.  I can't find that post either . I'm sure I said it somewhere.

I haven't had time to crack the tacho open yet but I'll have a look to see what my "107" prefixed speedo says. I'm sure it's original for my 350. I'll report back tomorrow.  It would be good to get a list of model specific speedo part numbers and model specific tacho markings. We're halfway there.

[s class]

koan,

That speedo marked to 240 with 52/87/145 change points is from a euro 280SE/SEL.  Mine has the exact same part number and markings.  Dont be mislead by the 107 part number.  Since the 107 series came out befor ethe 116 seires, any parts that the two series share will usually carry the 107 number.  (or even a 114 or 115 number if they date back that far). 

Oscar, that unusual tacho with the 6600rpm redline and the 300rpm start limit is probably from a later model R107 with an all alloy engine.  My guess would be a 300SL, but if indeed it is for a v8, my guess is a 420SL. 

Ryan

[chazchuzzlewitt]

does this look correct for the 6-cyl? it's advertised as being for the 280 6-cyl but all the tachos I've seen in european 280's have the redline starting at 6500 rpm...

http://cgi.ebay.de/ws/eBayISAPI.dll?ViewItem&ih=005&item=150047429897&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1

[s class]

Chaz its hard to say.  I agree that all the euro 280's I've seen redline from 6500rpm.  The clock also looks unusual. Both my 280SE euro and 450SL euro have only the hour ticks around the circumference.  This one has every 5 minutes marked.  But it may be a slightly earlier version (both my cars are 1980)  Generally the lower redline would make me suspect a V8, but the seller seems adamant its for a 6 cylinder.  WHat about a 280S?  That may well have a lower redline limit for the carburetted version, but I've never seen a 280S with a tacho.  But like all other cluster related things there were probably different variants for different markets. 

That's my guessing for today. 

I see the bid is 12EUR.  You could just take a chance for that, its not a huge amount of money.  I'm not sure what these things go for in europe, but here inSouth Africa I would expect to pay a lot more than that. 

[oscar]

Re the clock, mine has minute markings, bigger 5min markings and bigger still 12,9,3,6 hour markings.  Basically the same as chaz's link.  Mine being '73, I'd agree that earlier clocks look this way. The redline's completely different though.  What's a regular 450 redline at?  I don't think anyones posted that yet.

[s class]

Chaz,

So much for my assumptions on the price of tachos.  I have phoned my local specialist Mercedes breakers that I frequent.  They are a "high class" breaker that strips cars, catalogues everything and displays it on nice shelves.  They have a selection of 280SE W116 tachos going for ZAR150 each.  That's about 13 to 14EUR.  If you are interested, I could purchase one, test it on my car (also a 280SE) to verify its correct operation and post it to you.  I'm not sure what the postage would be, but I assume it isn't too heavy.  Interested?

Ryan