I think it was designed that way assuming that most people live in varying climates and wont want to connect and disconnect the heater hoses everytime winter or summer comes. For those that live in the South and never leave that area, then clearly you can disconnect the heater core(s) and just run the coolant through the engine. But for guys like me, who live in NY, the arrangement is fine, now that is starting to get cold and in the spring why would I bother disconnecting the hoses? Too much work and why make a mess?

 

RacerX, I know what you mean but computers and thermostats have been in cars for more than 30 years and if they were put to better use where HVAC is concerned we should not have to deal with a one size fits all solution. And we should certainly not need to manually disconnect and reconnect heater hoses. I am all for making the machines work for us, not the other way around and a little thoughtful design and engineering would have done so in this case. My final solution was to bypass the solenoid and connect the vacuum hose directly to the heater control valve so that the front heater core is always bypassed and thus remains cool until I disconnect the vac hose and allow the coolant to flow again. This will work for most of the year and when the temperature dips way down in the 40's as it does occasionally in the winter I can reconnect it for a month or two with little adverse affect.
Thanks for everyones thoughts on the heater issues.
Bill

 

I have noticed in the mornings when driving to work that even when the HVAC is "off" if the temp is set to something the air blowing out will be warmed to that temp.. i.e. I last had the AC set to 76 even with the system off the vent air will blow out at 76 or at least warmer then the outside air...
I have also found that you can set 2 different temps on for the AC and one for what the vent will blow when the system is "off"

With the system off press the temp up or down for the vent temp
if you turn the AC on it will go to what ever temp you last had it set to regardless of vent temp setting..

I found this out while going to work one cool morning and noticed it getting warm in the truck....