Hey guys,

have a couple of questions regarding my c200 1995.

I have just discovered my thermostat is knackered and am replacing it. Will running the car with a stuck open thermostat cause any performance or other issues?

Also, I have noted there is a small black knob by the OVP, numbered 1 - 9. It is labeled HFM MFM or something simular. I cant see as it is worn off. It looks like the EZL adjustment on older euro spec cars. Anyone know what it is?

josh

ok the adjuster knob has the following part number

025 545 50 58

this may assist with finding out what its purpose is

are you sure the number is correct? it doesn't show as a good number

ok....heres whats written on it.

025 545 50 28
09 9251 25
HFM MS

It will just take a long time to warm up especially in cold weather. Your heater will also be ineffective.

heres a pic. You can see the part to the right of the OVP

Attached Thumbnails

 

bump

the number you originally posted was different than the actual number, that is why it was invalid. anyway that is the coding plug, moving it will alter the ignition timing of the engine

Any idea on what the positions correspond to.

I Run on 95 RON octane, what position should it be set to for this fuel.

Just an interesting note, the engine doesnt ping on 91 RON which i thought was a bit odd

Ive been searching, and ive come accross something interesting. Apparently this plug alters MKV / ROZ coding. MKV = Multiplicative map adjustment,
ROZ = Research octaine number.

So, in saying that, it would control more than ignition timeing.

Would it change mixture ect to a different map?

And being named ROZ coding, would a higher number setting correspond to a higher octane rating?

josh

I have concluded that a higher number on the dial, gives more ignition advance. the position marked 7 gives approximatly 2 degrees advance, IE a higher octane gas.

But this contradicts what Ive read in previous posts about a higher number giveing more retard