Yesterday, since I had the ABS light coming on the dash board, I reset the codes on OBD1 code reader on my E320. ABS light is back on the dash board. However, I could not find any codes for it. Any advise?

Unfortunately the is no onboard diagnostics for ABS in a '94 E320. Usually ABS faults are OVP relay and wheel speed sensors (broken wires where they flex). When you replaced the relay was it with a new one or used?

Wheel sensors can be checked with an ohmmeter at the connector to the ABS control module located behind the battery. Left front is between pins 4 and 6, right front 21 and 23 and rear 7 and 9. I don't remember what the resistance is but they should all be around the same value.

Did you ever get your climate control system working?

Did any engine codes (pin 8) re-appear after clearing and driving? Any electronic throttle codes (pin 14)?

I have replaced OVP relay with a used made in Germany relay. Since that time the car is starting up and it runs too. However, the ABS light in my 1994 E320 sedan stays on all the time after I turn the key on or start the car. The self test diagnostic module (DM) 16-pin rectangular box located in front of the battery blinks six times when the button on the DM is pressed and released after four seconds. What additional diagnostic can I do to find out what is triggering the error code and why ABS light stays on all the time? Previously I was getting code 24 too, but is not there now. Some times the engine revs when idling but stabilizes and settles down in a few seconds.

I missed to mention that the A/C, heater and blower motor used to run but not any more. Nothing really happens to them when I switch them on.

Check your codes on pin 14. May give more clues to the DM codes.

Before you get into the climate control system very far, spin all the fuses. The aluminum ones corrode on the ends. Best solution is to replace with copper or brass ones. Also check the large blower fuse in a separate holder just in front of the fuse box. Touch it to check for a hairline crack.

I have replaced OVP relay and Brake light switch, and replaced front brake pads as they needed replacement on my 1994 Mercedes E 320. ABS light is constantly on. OBD1 has a button so I don't have to use tester and I don't have on. After depressing the button on OBD1 for 3 - 4 seconds, it light blinked six times first time and 16 times second times. I suppose it is showing error code 6 and error code 16. I tried to reset the codes but it still comes up with the same codes and codes have not cleared. It also continues to show ABS light on all the time. Any suggestions about how to get rid of these codes and ABS light? Other than that E320 is now running OK.

Your push button on the 16 pin connector only gives codes stored in the diagnostic module.
Much more information is available using an inpulse counter in pins 8 and 14.
You can also read codes in your climate module (pin 7) and SRS (pin 6).