I just had my carbs overhauled and now my W123's engine runs a lot better. I noticed however that when the temp reaches around 85.0C the idling becomes a bit rough and the oil pressure guage goes down to "2". The mechanic said that my auto choke is faulty. He said the Choke housing should feel warm when the engine starts to warm-up but in my case it does not so he's certain that it's shot. The two hoses that go to and from the thermostat does get warm but not the housing. I've checked the DC supply and it seemed OK. Does this DC supply actually heats the choke or is it a control for the choke? Is there a chance to repair or should I replace the whole choke assembly?

The electric heater starts the choke to open & then when the engine gets hot enough the hot water will keep the choke open.
Both are required for correct operation.

__________________
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

So what happens if say the heater is shot but the water temp sensor is still good? Would it still be able to control the choke? I live in the tropics so the temp never goes below 70.

If you open the choke up a little on that carb so the engine doesn't run too rich you should be OK.

__________________
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

guess I'll try that. Thanks DOC.