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Heater Control Valve

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4.5K views 5 replies 3 participants last post by  Enola Gaia  
T
#1 ·
I know some of you have had this issue before - I have an 04 tacoma and my heater control valve won't open all of the way. When i turn the switch from hot to cold in the truck the valve will turn almost all of the way but it gets to a certain point and then toggles ("thinks") back and forth and will never open completely. I took the cable off the valve and manually have it opened all the way at this point but I am not sure what I need to do to fix this and/or how in depth it will be.

Do I need to replace the valve or is it something else in the system that needs to be checked? I searched but only came up with people having issues on 99-00 models which evidently have a little different set up.

Any help would be appreciated!
 
#2 ·
I'm not sure what the specific problem may be, but the general outline of the problem is this ...

Up through the 2000 model year the HVAC controls were 'mechanical' (cable-actuated). You moved the lever; the valve (or whatever ...) changed directly.

The 2001 - 2004 HVAC controls are servo-mediated for most functions. You change the settings on the dash, and a circuit board translates these into 'instructions' for the servo motors.

The problem you describe could be mechanical (i.e., a glitch with the valve itself or the connecting cable). It could also be electrical. The worst case scenario would be that the main controller circuit board is 'shot' somehow.
 
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T
#3 ·
Hmmm....thanks for your response. Do you think I should try to assess the problem myself or would it make more sense to take it to the stealership? This is my daily driver so I don't really want to tear it apart the dash and have to leave it apart for days but at the same time I don't want to give the dealership all of my money unless it would be worth it's weight in gold. I have heard taking the dash apart can be somewhat of a cumbersome process.

Would it help if I took a video of what the valve is doing?

Thanks.
 
#4 ·
The problem is this ... Without knowing where the glitch is, it's impossible to know how much hassle it will be to deal with it. If it's a simple matter of control mechanicals at the valve, you might be able to handle it. If it requires getting to the servo motors or innermost ducts, it could involve deconstructing the entire dash area. If it means the circuit board behind the controls needs to be replaced, it could be a minor labor job with a big parts bill. I just don't know ...
 
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V
#5 ·
Do you know the part number for the HVAC controller? The spec for testing it calls out for about 3k ohm between pins 13-11. I'm only getting about 2.5k ohm so im not getting full cool on my control. I have a background in electronics and if I had the schematic for the part, I'd probably be able to figure out the failed component. If I can order one I could do a compare and contrast between a new and a bad one and if I'm able to fix it, I'd either keep it or let it go on ebay. There's a moderate amount of electronics on the board so without knowing more I'd have a hard time reverse engineering it. Any help would be appreciated

Thanks
Virgil
 
#6 ·
The PNC number for the 'amplifier assembly' (the circuit board thingie alone ...) is 88650B.
 
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