Hey......how does the 86 190E control the change in temp (amount) of coolant to the heater? There is what appears to be a small electric motor/valve on the left side of the engine compartment w/heater hose going to it. Two wires go in to it as well, if this is the bugger, does one wire increase the water flow and the other one decrease it? If so, how can you test it? How much voltage is used to move it and where does it get its signal? Thanks!!!!

The water control is done by a vacuum operated gate valve. It is either on or off. Temp control is done by mixing cool and hot air with a mode door.

The device you ask about is probably the auxilary water pump.

ChinaClipper,
I'm not sure about your 190E, but if it is similar to my '84 500SEC, you may have this problem: The Aux water pump that Steve talk about is correct. Providing your vacuum controls all work, it may still be under the hood. On mine, there is also a bypass solenoid that actuates when the climate control says "make it colder". It is located near the aux pump (which you will hear and feel the aux pump running when the climate control is turned all the way to "hot"). The bypass solenoid actuates a plunger which stops the flow of coolant to the aux pump, making it colder by not allowing coolant into the heater core. To make it warmer start by doing this: If your car is equipped with a bypass solenoid (it looks like a square plate with 4 screws holding it in, with a button in the middle raised up about .300 of an inch. the whole thing is silver in color) with the car running and warm, disconnect the bypass solenoid. It has two wires in one clip going to it. Nothing should happen. Take the climate control and move to it the "coldest" position, turning on the A/C. Reconnect the solenoid paying attention to wether or not it actuates. If it does, that part of it is working fine. Actuation will be brief, so have your second hand on the solenoid when you plug in the wires. If if doesn't actuate, it may be stuck or not working. Default on this is in the open "heat" position. Secondly, allow the car to cool down and remove the pressure from the radiator cap. Remove the four screws for the bypass solenoid. Carefully remove the solenoid from the plastic housing. There may be a little corrosion in there creating resistance. None or very little anti-freeze will come out since the level of this thing is the same level as the reservoir. Once removed, the solenoid has an E-clip at the opposite end, followed by a screen filter and a gasket at the top. My problem was this broken gasket. The gasket applies cooling system pressure in the opposite direction against the solenoid, isolating it from the coolant. Broken gasket allows the plunger to fall (get sucked down) by water pump and aux water pump vacuum. The answer is to replace the gasket (which I have yet to do). My temporary fix was to remove the E-clip and filter, so if the plunger did get sucked down, water would still flow, giving me heat in the car. This is a little risky if your coolant system is rusty or has a lot of debris in it. It also becomes a "full time heat" until you re-install the plunger. So save your parts. I'm not sure if just the gasket is available. If this is your problem, I hope it helps. Good luck!!!

Paul, your description sounds like the "monovalve" water control valve which is a pulse width modulated control valve (which means it can control, quantitatively, the amount of water flowing).

The 190 doesn't use this type of system. It uses a simple vacuum operated "on-off" gate valve. It does temp control in the dash with mixing of hot and cold air.

I found it so interesting one day when we received two MB heater valves. One was a valve for a 190 and was less than $20. The other was the dual pulse-width controled, aux pump contained, water valve for the 140 chassis at less than $800.

The 190 was one of the last cheap-to-repair-heater-system-equipped cars...(besides the ocassionally leaking heater core)

greetingz,

So how important is the auxiliary water pump with regard to heating or the circulation of coolant in the 190?

Heater problems
 

My 1986 190E 2.3 blows cold only out of the right hand side controls. But the left hand side is ok. What can i look at. Thanks.