lysinger

I've been fixing up a 1980 300TD wagon, my first Mercedes ever, and the heat stopped working when I changed the fan belts. I know it's not the belts fault

I checked the monostat and the rubber was torn up so I replaced it. I still have no heat.

I warmed up the car and the coolant hose to the auxiliary water pump is warm and the hose past it is not.

I assume this part needs help / replacement, but I have a couple questions about it:

If this part is broken, will it prevent coolant from circulating past it?

Is it always pumping when the car is running or is it switched?

If it is switched, where is the switch that controls it?

All help is greatly appreciated!

lysinger

As an update, I pulled the aux water pump and jumpered it to the battery and it works fine.

The monostat electrical connectors were all corroded so I cleaned them up.

Still no dice.

240D 3.0T

Did you get heat with the pump jumpered?

Make sure the monovalve is getting voltage when you turn on the heat.

bicylindrico

What is your engine temp? You need a warm engine for heat. Does your blower work? Give us more.

tanktube67

i think it has a valve that open the circulation of the water