I think I just got an incredible deal on a 300CD but it does have a few quirks....

it's got two buttons left of the steering wheel and below the speedometer built into dash.... I asked the seller what they were and she said one might be the fan on radiator and the other lit up the dials.... I'm not sure that either one do what she said can someone suggest what they might be? BTW.... it is a biodiesel retrofit and everything seems to have been restored.... but it does have a lot of miles 362,000 but i've owned other MB diesels that were not even close in condition and performance at a lot less miles!

So another concern, is when I make a turn there is a clunk in the engine compartment... could this be engine mounts? or rather suspension bushings?

one other thing, it's obvious that the differential was changed out.... when I go through speed checks when I'm doing 32 I'm actually doing 25... will that ratio stay the same through all speeds.... I need to know when I'm doing more than 70

Thanks for your help!

Could be the speedo head was replaced to account for the difference in readings. No such buttons stock, got pics? EDIT: I didn't read your last part, about the diff being swapped. That would definitely cause some speedo issues. As for the buttons, some below are saying the rheostat and trip odometer reset/clock setter things. I didn't mention them because they are in the cluster. OP's wording makes me imagine two separate buttons not on the cluster.

Could they be the rheostat for the dash lights and the trip odometer control?

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

I agree with kerry - rheostat and trip odometer.

The fact that the speedo is not accurate, does not surprise me one bit.
Even if you have 75 series tires instead of the 70's, it wont give you back the missing 7 mph.
Do check the indicated speed vs actual speed, at different speeds. (repeat in the summer)

__________________
It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

I've got an '85 rear diff. in mine, and put the '83 speedometer back in after the '85 speedo chewed up its plastic gears. The earlier speedo reads about 5 mph faster than I'm really going (measured with an old Garmin GPS unit) and the difference is always about 5 mph.

__________________
95 E300D working out the kinks
77 300D, 227k, station car
83 300CD 370k, gone away
89 190E 2.6- 335k, no more
79 VW FI Bus- 145k miles, summer driver
59 VW Beetle ragtop- 175k miles
12 VW Jetta- 160k miles

If the buttons are not stock, I would think part of the former bio operation. Or maybe the entire cluster was pulled from a unit that had an idle adjustment knob.
The clunk may be mounts or maybe a failed guide rod (tube).

__________________
83 SD

84 CD

the switches are not stock of any kind... one is blue and one is green.... not dash light related or odometer... they are not in the instrument panel but below it built into the dash next to the steering wheel column on the left side....

thanks for the inputs

Those are probably for the WVO system. Heaters and maybe something to do with switching tanks (if it has 2 tanks).

You can get under the car and look at the diff. to figure out your rear end ratio really quick. On the left side of the diff. (facing the diff.) look at the bottom left corner and scrape off any paint, grease, etc... For that year car (if it is an auto.), you should see 3:07 on the little tab. Anything else and the rear end has probably been swapped. If it does say 3:07 and it still has the factory tire size... Then the speedo has probably been swapped.

__________________
AJ

1985 300D (SOLD)

That sounds quite logical but there are no extra tanks and everything runs quite well without their use.... no heater either as I am in Nocal and not necessary.... I haven't followed any leads yet though as in where the wires lead to.... just thought I might ask what everyone would think about such switches

Thanks