I've just replaced the heater control valve, old one was a bit leaky. Now at the max hot setting it only blows hot air for about 10 seconds before it goes lukewarm. If I turn it down to full cold then back to full hot it does the same thing again. Anyone any thoughts as to why it's doing this?
Heater control valve problem (1 Viewer)
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Check that the heat control valve was installed correctly (don't think it's possible not to however), then check the cable connection to the valve lever to see if it moves the valve in the correct directions when you move the HVAC temp control slider.
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- #3
Thanks. It's definitely installed correctly and the cable moves the valve correctly as well. My thinking is it needs a good flush. The coolant is a nasty colour and hasn't been done for probably 5 years.
Malleus
Far west of Siegen
Sounds like the blend door. I'd check the solenoid and motor (details are in the FSM; there's an excerpt just for this HVAC section in the Resources section). It's unlikely the coolant has anything to do with the problem, unless you've got a massive plug in there.
What brand and part number valve did you purchase?
What uyear and model is your truck?
There are at least two valve that I'm aware of and they will bolt in the same place but operate differently. Since you're in Ireland, we need more info.
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Genuine Toyota for a 97 1HDFT diesel, part number was 87240-60170
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- #7
If you had Toyota or partsouq provide your part number, then you're probably good.
The differences are early (1991-1992) vs Late (1993-2006) and the valves operate the opposite direction of each other for open/close.
I think your diagnosis should point to the blend door.
Depending on version, some models got the auto temp control setup and have a separate computer module that controls this.
I'm not sure on those, but @OGBeno is the master.
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- #9
Many thanks - what/where is the blend door? Downloaded the FSM and couldn't see it
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And I should have said it was working perfectly before I changed the valve 
Then go back to the original one and confirm operation direction and make sure you didn't bump or disconnect something you shouldn't have.And I should have said it was working perfectly before I changed the valve
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Malleus
Far west of Siegen
There's a separate excerpt from the FSM for this area, since it's so commonly asked for, and it's a pain to find.
