I wouldn't be too quick to rule out the EHA as a contributor to hard starts. In any case, it's easy to run the diagnostic test. Ignition off for all tests:

1) Multimeter set to Ohms. Disconnect KE control unit (N3) coupling. Positive lead to contact 12, neg to contact 10. Spec: 19.5 ohms +/- 1 ohm.

2) Disconnect EHA (Y1) coupling. Positive lead to EHA pin 2, neg to pin 1. Same spec 19.5 +/- 1 ohm.

3) Positive lead to EHA coupling terminal 2, neg lead to KE coupling term 10. This tests the wiring from the EHA term 2 back to the KE controller. Spec is <1 Ohm.

4) Positive lead to EHA coupling terminal 1, neg lead to KE coupling term 12. This tests the wiring from the EHA term 1 back to the KE controller. Spec is <1 Ohm.

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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