Heater problems

I have a 1977 280SL Euro and don't get much heat out of it . It does not have AC. I changed the thermostat, but it didn't help. I flushed the system, and it didn't flow well in one direction but couldn't figure out why. cb

[MBenzNL]

Your 1977 euro 280SL probably has the 180 degree rotating temperature setting knobs that control the heater core water inlet valve by cable...These systems were very good and didn't break down as much as the current electronic systems...
If the engine warms up well and the heater core doesn't, you should check the water inlet valves to the heater core. There can hardly be anything wrong with them.

greetingz,

The heater control is a vaccum operated slide control on each side. The engine temp. gauge shows plenty of heat but not in the heater lines.

[hill]

There could be a vacum controlled valve at the firewall. It would connect directly to the supply side heater hose. With the engine warm, disconnect the vacum line and plug. If you get lots of heat the problem is in your controls/ vacum pods, modulators? Hell I can't remember what there called.