2006 Prius - Heater Flow Control Valve Question

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by daronspicher, Feb 5, 2015.

  1. daronspicher

    daronspicher Active Member

    Joined:
    Sep 27, 2005
    1,208
    0
    0
    I have a 2006, 155k miles, bought new Feb 2006. Have not had a lot of trouble or maintenance beyond oil changes and tires, one front wheel bearing, couple of 12v batteries. For purposes of this discussion, the engine coolant has not been changed since new. For the last 3 or 4 years, I have the check engine light on all winter and then it goes off in the summer. I don't bother to go find out what it's complaining about.

    My heater issue:

    I believe there would be a hot water line valve that is opened and closed when the cabin heater core needs more hot water or less hot water. Since I don't have a control lever that is cable connected to said valve, it must be electronically opened and closed by an actuator of some kind, driven by a computer request. This is my theory.

    I'm in Chicagoland so I pretty much 'get it' when it comes to having a warm car to drive in the winter. The thing has an engine the size of a Harley, it just doesn't burn enough gas to make enough heat. Summer is coming, live with it.

    My problem in the cold days with the heater on blower on full or 80%, is that every so often (and more often as we get older) it will blow cold. As if the fluid control valve is not opening. Then I can switch from floor heat to mid-vent heat to defrost and after 1 or two switches that control valve will manage to open properly and I get heat again. I even think I can hear a bit of a mousy wimper of it opening that valve when I do this, maybe I'm just wanting to hear it in my head.

    I searched around here and couldn't find a thread that seemed to address this issue directly, so if there is one can you point me to it?

    Am I on target with how this system is built and how it works, or can someone line it out for me?

    Is there a how-to write up on how to change it, or a video. If not, and if I can tackle this on my own I will make one.

    What parts do I need and where are they hiding on the car, can I get to them in the garage on a DIY day?

    Your advice is much appreciated!

    Thanks, -Daron
     
  2. valde3

    valde3 Senior Member

    Joined:
    Jun 28, 2014
    1,982
    725
    0
    Location:
    Finland
    Vehicle:
    2004 Prius
    Heater output temp is controlled by air flap. Air flap is controlled by servo.

    So heater output isn’t hot enough even with max hot temp setting and waiting for long enough so that engine is hot?

    Are you sure you don’t have air in cooling system? You need to check it from radiator itself not from coolant overflow bottle. If you don’t have air in cooling system you need to get fault codes read with Toyota scanner (normal scanners only read engine codes) (mini-vci is cheap) and/or you need to do actuator test.

    EDIT: exstudent is right only do those things if cell has nothing to do with cooling system. I somehow missed that part of your post.
     
    #2 valde3, Feb 5, 2015
    Last edited: Feb 5, 2015
  3. exstudent

    exstudent Senior Member

    Joined:
    Jul 11, 2009
    2,207
    863
    0
    Location:
    Torrance, CA
    Vehicle:
    2007 Prius
    Why didn't you get the CEL code read 4 years ago?

    Get it read for free at Midas, Auto Zone, or other large chain parts stores. Most likely P1121 (3-way coolant control valve issue). If P1121, just replace the valve and you'll regain heat. Also change the engine coolant and Inverter coolant! Way overdue and both cooling loops need to be properly bleed.
    P1121 - Coolant Control Valve Replacement (with pics) | PriusChat

    Also get the brake system flushed. Techstream software and mini vci cable required. If unfamiliar or uncapable, just get done at the dealer. Might be $100-$150.

    Get the transaxle ATF-WS drained & filled. Many procedures posted on how to do it; perform a search. Inferring you haven't done this as you haven't done the coolant drain/fill.
     
  4. daronspicher

    daronspicher Active Member

    Joined:
    Sep 27, 2005
    1,208
    0
    0
    I wonder if the hinge on the air flap is getting crumby, or the servo is needing replaced.

    I should check if the coolant level is low for any reason. It just seems like I can give it a little wack with a hammer (change from one heat selection to another) to remedy the issue, so I was thinking the computer is telling it to do something and then some physical part is no longer making the movement to deliver.
     
  5. daronspicher

    daronspicher Active Member

    Joined:
    Sep 27, 2005
    1,208
    0
    0
    You are correct on all of this, all of those fluids need changed out.

    I did see some P1121 threads, but after reading them I thought they dealt with coolant to the canister and not really about the cabin heat, so thanks for clearing that up.

    I just called my Toyota dealer to get an idea what kind of money it takes to get some of this stuff done. It was a bit of an odd experience. The lady who answered the service option line had no idea about doing service work, she was just typing what I said into some text box and setting up my appointment. I asked her what it would cost, how long it would take, and she had no idea and seemed a bit offended that I would ask. I helped her with how I expect things to be done and she is going to email my list to a service manager who can figure it out and call me.

    It's always fun to get the cost from the dealer so I know how many hundred I am saving by busting my own knuckles under the car.

    Thanks for the input, -Daron
     
  6. exstudent

    exstudent Senior Member

    Joined:
    Jul 11, 2009
    2,207
    863
    0
    Location:
    Torrance, CA
    Vehicle:
    2007 Prius
    There are you tube videos of people changing out this 3-way coolant control valve. Some of them do an excellent procedure. Luscious garage has a video of this procedure on their website as well.

    For whatever reason, the valve at times has enough "strength," to move to the correct position, thus the intermittent problem, and intermittent CEL light. For cabin heat, if the valve can not move to the correct position, you get to be cold, as you know.

    Don't know about the servo/flap. Fix this valve first, if the error code is P1121.
     
Loading...