Heater Control Valve

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Tremek said:
Does replacing the HCV require draining all the coolant, or can I expect to just dump what's at the top of the system in those pipes out as I replace it, and then run it again while elevated to bleed out air bubble I'm creating?
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You will lose only a very small of coolant swapping the valve.
 
Today my HCV just started blowing only hot air until it was all the way to the left. What could cause that?
 
Is it true that you will not get hot coolant to your rear heater core if your HCV is closed? Today I tried, and it seems like you won't. Since my HCV cable is disconnected on Mario right now (due to the in-cabin control not adjusting the HCV), that necessitated a pulled over manual adjustment so I didn't start shivering. After that, I had to run the rear heat extensively for the first time because there must be air bubbles in my front heater core (e.g. cold air after an initial warm period). But man, that rear heater works like crazy when it gets going.

Cold weather, man. :meh:
 
To the OP, before the massive high jack. I have the same issue, fist I tried over riding the cable and moving the valve to hot. Nothing. Both heater hoses are hot, inside is cold air. Removed stereo to find the servo motor which controls cable and a flap closing air off from heater core. Mine was jammed with antenna cable. I have pics on my phone and can text them to someone that can post.
 
quasi said:
To the OP, before the massive high jack. I have the same issue, fist I tried over riding the cable and moving the valve to hot. Nothing. Both heater hoses are hot, inside is cold air. Removed stereo to find the servo motor which controls cable and a flap closing air off from heater core. Mine was jammed with antenna cable. I have pics on my phone and can text them to someone that can post.
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I would love to see those pics! I think my 80 is having this exact same problem.
 
Ok, so the first pic shows the servo on top of the heater box, second shows the flap door, sort of. This is from the the fan box removed view. All you see from a complete truck is through the hole when the radio is removed. There is more room than it looks like, but not much
 
quasi said:
Ok, so the first pic shows the servo on top of the heater box, second shows the flap door, sort of. This is from the the fan box removed view. All you see from a complete truck is through the hole when the radio is removed. There is more room than it looks like, but not much
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Thanks for the description of the pics. So if a person wanted to manually open the air flap to the heater, where is that relative to the removed radio? Assuming the servo has failed?

I'm cold in MN and a little desperate to get heat in my 80! Even if it's temporary until I can solve the problem correctly.
 
quasi said:
There is a metal rod approx 3" long connecting the motor to the flap door. Look for little white clips similar to door lock rod bushings. Unhook and move door with cable together. You will pull toward the left
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Exactly what I needed to know! Thanks!
 
I'm super slow sometimes, but I think I've finally gotten it. This black device pictured is the heater servo. This thing fails and the air flow does not open with the heater controls. I could swear a lot and get those screws out and replace the servo. Or I could temporarily disconnect it for the winter and just open the air flap manually.

Right?

Heater Servo

Heater Servo

  • Media owner KellyC
  • Date added
 
With your help, I think this problem is solved. After removing the radio, I observed the servo binding as I changed the heater to the warmest setting. I disconnected the cable to the HCV, and everything else seems to be working. I'm guessing a new cable is in order.
 
Thanks Quasi and KellyC for getting he thread back on track and moving it forward. Sounds like some great info to solve this little issue.

Rick
 
Just to wrap this thread up for anyone else that finds this thread later... it seemed my HCV was working properly. My valves/flaps that controlled air flow were working well so I decided to look more at the heater core.

Even though I flushed the entire system really well through the radiator during the summer, I rethought the heater core. I decided to backflush it the way IzzyAndSue did it here:

Heater Core Flushing - OWNED!

Wow! I must have gotten a quart full of sediment out of that thing. Some pieces as large as a 1/4" or so. Now, 15 minutes after a cold start, I had 166* air coming out of my vents on high. Earlier this week I was getting upper 80's and lower 90's out of the vents. Needless to say, I'm looking forward to jumping in and running the heat. It was -11 where I live last Tuesday.

Thanks @Izzyandsue

Rick
 
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