rgnprof, yes you can just replace the switch, but it is no longer available new from MB, just the whole assembly for $350, as you have found out.

__________________
1988 California version 260E (W124)
Anthracite Grey/Palomino
Owned since new and still going strong and smooth
MBCA member

Past Mercedes-Benz:
1986 190E Baby Benz
1967 230 Inherited from mom when she downsized
1959 220S Introduced me to the joys of keepin' 'em goin'

There are only 10 kinds of people in the world--those who understand binary and those who don't

John,

Thanks for the documents. I looked though the online document and I also found Job 07.3-121 online, but both do NOT include my year and motor. Any of the specific tests are for 103 motors, generally up to 1989, maybe 90.

Does this matter? I know you said my M104 is very similar to the 103's.

ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

As long as the duty cycle reading is moving, the mixture is still being controlled.

Adjust the idle mixture to 65-70% and see if there is any difference.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

You have not read through this thread - I know, who has the time...Anyway, this is a brand new EHA valve - $190! Can't believe it needs adjusting - although I'm not ruling it out at this point.

Besides, I have read many contradictory reports regarding making adjustments to the EHA valve...

ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

And I appreciate the help. But it's a brand NEW valve - is it typical to have to adjust a new EHA valve? Everything else that I have read suggests no. Just checking - and thanks!

Ryan

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE

Ryan, I just read thru your earlier post, using the Sears meter. I have that exact one, and to get correct duty cycle you must REVERSE the leads in the round diagnostic connector.
Didn't search data on your 104 engine, but in my 103 manual, the 70% DC indicates no signal from the TD sensor. 30% indicates a bad coolant sensor, 50% is normal.

DG

Ryan,

All of the electrical components in the fuel system are on the same on your motor as in any 12V M103 from 86-92. So those tests will apply to you.

You are looking at a faulty potentiometer or that throttle switch. Rule out one or the other using the FSM.

As a side note to people who search this....the EHA should NEVER be adjusted, it it set properly from the factory. If you make adjustments to the EHA it is a band-aid fix for other problems such as vacuum leaks, worn FD, etc. The EHA currently on my car is a from a 4-Cylinder 2.3 190E, no adjustment was necessary or needed. If you have problems with an EHA, replace it, don't adjust it.

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1991 300E - 212K and rising fast...