Thermostic heater control valve operation

[chippers65300]

Can anyone explain theory of operation of the thermostatic heater control valve used on 65 Chrysler 300 with AC. Cable controlled to open and close but what's the purpose of the thermostatic control and copper winding that mounts to the case? I'm guessing as the heater case hits a certain degree of heat that the thermostatic control may open or close the valve to maintain a certain temp?? Mine is frozen and going to attempt to rebuild or send it off. Just trying to figure out how it works.

 

[CBODY67]

The "copper winding" is a capillary tube to fine-tune regulate the coolant temp in the heater core. More-consistent output temp is the desire. In prior times, it was common for the heater to get hotter while on the highway than in city traffic, as I recall. Some vehicles more than others. Consider that capillary tube valve a luxury as that part was deleted in later years, or in prior times (1955 Chevy cars had them too, but not later Tri-5 Chevies, as I recall), when "the accountants" figured they weren't needed (needed to delete them to cut costs).

Just some recollections,
CBODY67

 

[chippers65300]

Thanks for the info. Much appreciated!

 

[Ross Wooldridge]

Hmmm - it's my understanding that it was designed to prevent icing up of the evaporator core in overly humid AC weather. The capillary tube would open the heater core up just the slightest little bit for a minute or two to help melt ice buildup off the evaporator core.

Perhaps I've had it wrong all these years.

 

[CBODY67]

If the EPR valve is correctly adjusted, wouldn't that do the same thing (no icing)? On systems with EPR valves, that is.

 

[Ross Wooldridge]

I don't know - I thought the EPR stood for Evaporator Pressure Regulator, so my literal understanding using the meaning of the words (which could be wrong - lol) was that the EPR ensured that things didn't get too pressurized and potentially fail.

Additionally, I could see no reason why there would be an automatic functionality of limiting coolant flow for the heat circuit - if things get too hot, people just turn the lever down a tad... however, one might not know that the evaporator was icing up until condensate puddles occurred on the floor mat because the drains iced up (that's happened to me), and so the system can self regulate by adding a tad of heat to melt the ice build up and prevent that.

I dunno - that's how it was explained to me and it seemed to make perfect sense. The capillary tube puts pressure to open the system when fully closed against a small spring on the rubber stopper arm in the water valve, and that spring closes it when the capillary's pressure diminishes - thoughts? Am I backwards on that?

 

[chippers65300]

Thanks for all the responses. Much appreciated!