Good Morning Group,

While trying to research and solve my inoperative blower motor and Climate Control head I found this test on another Mercedes List.

I cut and pasted it here in hopes that someone else might benefit from it.

Check left side of engine compartment, up and behind brake
booster. It has red, yellow, and black wires on our two 124s. I wouldn't
expect the V8s to be different. There is an easy test using a voltmeter to
diagnose a bad blower regulator that was sent to me by the always
knowledgeable and gracious.

You can check the power and control signal to the blower at a plug
located above and behind the brake booster. It has 3 wires, black, red and
yellow.

With the plug in the socket and the climate control on, check to see
that you have +12volts on the red, a good ground on the
black and 3 to 10 volts on the yellow.

If the yellow wire voltage is a problem that points to a problem with
the control module.

If these all check out then the problem is with the blower control
module or the blower itself.

I performed this test and found that I had no ground. The other two wires and voltage were within limits. I might add that if you do not have long test lead probes on you volt meter you might not be able to reach back that far behind the Brake Master and the various other small items.

Fear not, a daughter with small hands and a need for Christmas money will do most anything to make dad happy. She got the test probes on the proper colored wire, and lost paitence with me before I finished telling her what I wanted.

__________________
BeachGuy

1994 E320 Wagon