R129 / W124 heater system ( other cars too? )

[97 SL320]

I'd post this in the SL section, but there is a wider audience here.

R129 97 SL320 ( W124 E class, maybe others too )

In addition to the large heater hoses connecting to the heater core, ( one on each side of the air box ) there is a small hose on each side. I can't see the end of these hoses but they point towards the base of the windshield. The right side small hose makes a stop at what looks to be a valve on the air box. Any idea what these small hoses do? ( These are not for heated windshield washer fluid, a second set goes to the WW bottle. )

Second, there is a electric water valve for the heater, is this a on / off type or modulated?

At some point I need to change all coolant hoses. Being this is a summer only car, the heated WW bottle will be bypassed as well as the mystery small hoses if they are not vital. Bypassing the small hoses would save $ as the molded T hoses are going to be big $.


Thanks

[emerydc8]

I read somewhere that Mercedes uses the hot water to melt the ice/snow at the base of the windshield, near the windshield wiper. I can't find much information about the system. Maybe someone else can chime in.

[S124300]

Our W124 heater, not the a/c model, only has the feed and return hoses from the cylinder head and a connection to the electric circulation booster pump.

[97 SL320]

I suspected some sort of lower WS heating. These will be bypassed as this is a summer only car. The circulator pump will be bypassed too, I'm reading that on some models, this pump can lock, burn the control module and sometimes take the car with it.

Finding out if the electric heater water valve is on-off or modulated is the only question. I'm OK with installing a manual valve under the hood, I've done this on other non MB , non AC cars. Shutting off water makes a huge difference in the summer. Even if the flaps are set to cold, some air leaks past and you still have this hot mass tucked under the dash radiating heat.

[Jer]

The monovalve (heating valve) is on-off. Pulse width modulation is used to control the volume of coolant moving through the heater, which in turn affects the temperature of the delivered air.