I have 2 problems, (1). rough idle even though I changed the timing chain. the OVP has an unblown fuse in it . (2) the heater fan goes on only when it wants to if at all. The local Benz dealer wants $75.00 just to read any codes and I don't have a HHT, so any help would sure be welcome Thanks

When was your fuel filter last changed? Spark plugs??
Very possibly could be the fuel filter. That is what caused a rough idle for me.

What services have been done? There's about a bazillion different things that can cause rough idle. Your car can have codes retireved by an impulse counter the HHT is not necessary. The electronics on your car are not that sophisticated, meaning that if there isn't a fault light on a code check won't reveal anything.
The blower could be just a faulty switch.