OK I'm starting where my question ended.....All warning lights, gauges and dash lights were not working, checked all fuses..ok. This is 4 the 1998 c200 benz i just bought.

Have you checked the dash dimmer switch to see if it's on fully?

check bulbs, fuses , switch process of elimination, nothing else for it

New thermostat, installed, saw, new coolant made a little mess filling reservoir, (normal) checked fan fuse for some reason, and condenser fan fuse (xxx ?:), and temp guage, is slightly lower on gauge (than normal?) (disconnected xxxx? quit? a bit? to get to thermosta?.t no dash warning lights have a feeling I popped a relay.

Answer:

ok, you did a coolant service with STAT,

and it failed.

tell us what works right and wrong, symptoms only.

over heating? parked, (fan never comes on)? as it hits 225F?

under heating? ( fan stuck on , up North can cause huge cold engine)

dash gauge stuck low. (thermostat wrong heat range 180f is best. see FSM for spec. on this temp. spec..

Dash guage varies.? oddly (air in system)?

Dash gauge too high.? (Stat put in upside-down or bleed hole (jiggle) not UP side. higher side of mount , trapping air.)

Does something wrong happen only driving?

leaks?

does cap on rad hold 12-14psi pressure, hot.?

if car has fan belts, are they tight? (for sure water pump does)

You mean by gadgets, warning lights and gauges? That would be from the ignition switch's run wire, the wire from the on position. This wire sends voltage to the ignition system, and to the dash for the warning lights and gauges-but not directly to the dash-the signal would reach the dash after being routed through the fuse panel to a fuse for the dash gauges and warning lamps. You need to check if that fuse is good.
Recall seeing any wiring diagram? The fuses are labeled either "hot at all times" or "hot in run or start". The fuses labeled hot in run or start are only sent power when the key is on, so power for those fuses are routed through, or turned on by the key being on. Depending on the car and its wiring set up, many will have relays that are turned on by the run wire, and power is then sent from the relay to that circuit's fuse in the fuse panel. This relay may be called the ignition relay. Or your car may have a different relay to send power from the run wire to the fuse panel.
The only way to figure yours out is to see a wiring diagram for it. Then you will see how power is sent from the ignition switch to the dash.
Wiring diagrams are almost always found in repair manuals. Check if your library has a manual for your car. Most libraries have quite a few repair manuals. Or parts stores sell repair manuals too, for about $25. Try to find a Haynes repair manual for your car. The other popular repair manual is from Chilton. My preference is Haynes, just my preference. I been burned by Chilton manuals sooo many times-incomplete wiring diagrams, incorrect information, incomplete information. Haynes are not perfect by any means, you want perfection-spend big bucks for a factory service manual ! In general, Haynes is more complete than Chilton.
OK, enough venting. If you have a test light, check for power at the fuse for the dash (may be labeled "gauges" or "instr pnl", something like that) with the key on. If it has power with key on, wire from the fuse goes to the dash. If that fuse has no power to it with key on, power has been lost between the ignition switch and that fuse-now you definitely need a wiring diagram to find the problem.

GAUGES NOT WORKING

If all voltages checked ok, then most probably its faulty instrument cluster board on which gauges are connected. Yes if cluster circuit board looks ok, then also it can be faulty. Somewhere there is minute short or burn on board then such problem arises.

Also check the fuse box. One under hood and other under dash.

Inspect each and every fuse and see if all are fine or not.

Click the link below for complete step by step troubleshooting:----

http://alltypesofpartsreplacing.blogspot.com/2012/12/no-spark-faulty-spark-plugs-replace.html

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Thanks.

Sounds like a fuse or an earth wire loose in the cabin. Take the fuses out and chk them in the light. Go thru all earth wires both in and outside the cabin, something is loose if not a fuse, remember fuses in the engine bay. cheers

If you check the oil pressure with a mechanical gauge and the pressure is steady, the problem would be in the gauge on the dash if you have replaced the sending unit and there are no problems with the circuit.
The mechanical gauge could verify a problem with the actual pressure in the engine.

Turn on your front and rear lights but not the headlamps, if they are on but the dash lights are not, check the dash lamp dimmer and check every fuse electrically using a test probe or multimeter. If the external lights are not on, again check fuses electrically and then go through each area of the circuit, like switches, relays etc. Again, use a test probe which you can buy from any auto parts store, clip the clip to a good ground (on the vehicle body) and probe each connection with the pointy end. If the probe lights up, power is present, if not, go back and start again. Fuses should light up the probe on BOTH ends of the fuse. If the probe only lights up at one end of a fuse then that fuse is faulty and should be replaced. If the fuse does not light up at either end of the fuse, then that fuse does not have power connected (as the ignition should be OFF, you will see most fuses without any power) or the light switch is turned off or faulty.

defective contact switch

Checked Every fuse in the fuse box (no small task).This includes #4 - Power point Instrument Panel, #14 - Day time running lamps (auto lamps doesn't work nor does auto lock), #27 - ignition switch run feed, #35 - Instrument Cluster, #41 - Instrument Cluster, #42 - Delayed Accessory, #45 - Ignition switch run/start feed, #102 - Door locks body security module, #103 - Ignition switch, #110 - Ignition switch, & #116 - Ignition switch. But I also check all other ones as well, they all register OK. AC panel & radio work. Turn signals work. Mileage does not work, trip computer does. So, basically, everything works except auto head-lights, auto locks, and the dash cluster (no MPH, RPM, mileage display, Fuel, Temp, Tran Temp, and Oil Pressure).