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Discussion Starter #1 (Edited)
About 5 years ago I took off very early on a 25 degree morning on a 250 mile trip to Santa Barbara. Half way there my heater suddenly began blowing cold air (???). About 20 miles further down the road I stopped for gas and when I resumed my trip my heater was blowing hot air again. That odd heater operation has bothered me ever since as I could never understand why it suddenly began blowing cold air that morning. Early this morning on a trip to Fresno my heater began blowing cold air again and I did some serious thinking about what could cause such a bizarre operation again. I turned my A/C/heater selector switch OFF for a minute and when I turned it back ON my heater began working normally again. It acted like the heater control valve somehow shut while I was driving at a steady speed and when I turned my selector switch OFF it relieved the vacuum in the heater control valve's diaphragm. Now I'm wondering if my 7 port selector switch is leaking internally; allowing a VERY slow vacuum buildup inside the heater control valve's diaphragm. As thermostats don't just "fall open" while you're driving at a steady speed and then recover an internally leaking selector switch makes a lot more sense. Do any of you have any other ideas about this bizarre heater operation?
 

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When this happens have you checked your AC compressor to see if it's engaged? I suppose with the right vacuum leak maybe it's acting like you've switched to AC mode. Is there a device in line with the heater hose that shuts off the hot water going to the heater core when you normally turn AC on. I know the factory AC on my '67 did that and now the Vintage Air AC/Heater system that I installed does that also.
 

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Discussion Starter #3
When this happens have you checked your AC compressor to see if it's engaged? I suppose with the right vacuum leak maybe it's acting like you've switched to AC mode. Is there a device in line with the heater hose that shuts off the hot water going to the heater core when you normally turn AC on. I know the factory AC on my '67 did that and now the Vintage Air AC/Heater system that I installed does that also.
My A/C compressor isn't spinning when this happens. It's just ambient temperature air that comes into my cabin. That's why I'm now suspecting vacuum is slowly leaking across the flat inner faces of the 7-port vacuum selector switch JUST enough to close my heater control valve after many miles of driving. By shutting my 7-port vacuum switch OFF then back ON restores my heater to normal operation.
 

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Discussion Starter #5
Sounds reasonable toobroketoretire! Good luck!
The bizarre heater operation is the least of my worries right now. Over the past 73 years plaque has built up in my abdominal arteries to the point in which I can no longer walk as my leg muscles are starved for blood. I desperately need an "open" surgery but because of this pandemic the surgery is being delayed until the pandemic is brought under control.
 

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toobroketoretire ... I can understand your concern about going through surgery during this COVID-19 thing. I pray your given the strength and comfort to get through what your dealing with and can get yourself taken care of. John
 

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Discussion Starter #7 (Edited)
toobroketoretire ... I can understand your concern about going through surgery during this COVID-19 thing. I pray your given the strength and comfort to get through what your dealing with and can get yourself taken care of. John
I want to know why the plaque formed inside my lower arteries in the first place. I read plaque consists of fat and calcium so I'm wondering if my love of ice cream and dairy products caused it. And then there's the bruises I get on my arms when I bump into things. Big purple blotches caused by the capillaries under my skin rupturing. And my hair loss. And my vision loss. And the loss of my teeth. And the loss of my ability to uh "perform". Getting old isn't as fun as I thought it would be.
 

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I'd say if you're not already seeking serious medical advice you need to start. I remember my elderly neighbor always saying "Getting old ain't for sissy's". Good luck toobroketoretire.
 

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Discussion Starter #9
I'd say if you're not already seeking serious medical advice you need to start. I remember my elderly neighbor always saying "Getting old ain't for sissy's". Good luck toobroketoretire.
I just got scheduled for my SIXTH surgery on March 17th. The doctor told me the three stents he installed a month ago are plugged up with plaque. This is wearing me out.
 

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I hope your surgery gets you taken care of and your doctors get everything figured out and taken care of so you can get back to doing the things you want to do. 🤞
 

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Discussion Starter #11
I hope your surgery gets you taken care of and your doctors get everything figured out and taken care of so you can get back to doing the things you want to do. 🤞
Fortunately we live during a time in which we have the most modern diagnostic tools that can see what's wrong in a matter of a few minutes. Had I been born 100 years earlier I would remain crippled until my final curtain.
 
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