A/C not working after coolant control valve replace error P1121

The HVAC system doesn't depend on this valve, but many folks, at least at first, think it does... Your problems are elsewhere.

Similar symptoms as yours happen when the inverter cooling pump is going bad because when the inverter starts running hot the first thing it cuts back on power distribution for is the AC.

Get a hose and connect one end to the bleed valve and put the other end in the inverter reservoir then open the bleed valve to see if there's air in the system and confirm the pump is still pumping coolant into the reservoir. If that checks out let us know and we'll next steps...

And with any HVAC problem first thing you want to do is replace of remove the cabin air filter so lack of air going into the system isn't an issue.

 

It was good to fix the control valve problem, but it wasn't your A/C problem anyway. A bad control valve can sometimes cause you not to get heat when you want heat. On the other hand, if you're getting heat when you don't want it, that's something else, not the control valve.

So you just had two problems, one with the control valve, now fixed, and one with deficient A/C (or too much heat), that may be intermittent enough to have fooled you right after the valve was replaced, but hasn't been identified or fixed yet.

How hot is the air you're getting when it "blows hot"? Just not cooled? Or actually heated?

 

It's a little more subtle than that. The valve does divert flow away from the heater core when it's in the 'preheat' position, pumping hot fluid from the thermos back into the engine before startup. So if a bad valve gets stuck in that position, you can end up with no heat when you want heat.

However, the valve is not involved in a story like this, getting heat when you want no heat. You're getting heat, so clearly the coolant is flowing through the heater core, so this valve is not at fault.

If it were only blowing not-cooled air, that could indicate a problem with the refrigerant system. But because it is blowing air that's actually heated (and noticeably more heated when the engine makes more heat), that means the air is passing through the heater core when it should not be.

There is a movable door inside the heater unit that directs air either through or around the heater core (or a mixture between). When you are trying to cool, not heat, the car, this door should be in the position where none of the air goes through the heater core, and all goes around. Your air mix door seems to be in the wrong position.

Here is a thread with some more information on that:

No, that wasn't a mouse in the heater | PriusChat

 

Yet again, you know too much to understand my point. As in, I've known more than one person who when told there's a problem with their three-way coolant valve they think the word "coolant" means that once this is fixed their problem with the air conditioner will be fixed. That's what I was speaking to... As in your engine, heater and inverter coolant is a different system than your AC.

 

If we wanted to, we could converge on something that makes sense. As in "if you want hot and can't get it, the problem could be this valve. If you want cold and can't get it, that won't be this valve, has to be something else."

That works for the people who use "A/C" to mean the whole HVAC system, the people who use "A/C" to mean only the refrigerating parts of the HVAC system, and the people who use "A/C" to mean "whatever the thing is doing when I want cooler air". We've had threads with people using the term all of those ways, with some threads getting weird until everybody realized what everybody else meant.

In a situation like this thread, where someone has asked for cool air and is getting hot instead, it doesn't help much to say "your heater is a different system than your AC". It sure doesn't feel like a different system, when even though the refrigerating bits are working, you're still getting hot air. (And the feeling is right: the whole reason that can happen is the systems aren't so separate after all.)

I'm also not sure why you grouped "inverter" in there with engine and heater. The inverter cooling system is the one that really is separate, while the engine and heater (and thermos) are all in one loop, and very able to affect the A/C.

It's certainly not accurate to say "the HVAC system doesn't depend on this valve", which was the way you put it in #2.

So I think it is most helpful to give people the simple rule for when this valve might be their HVAC problem, and when it can't be. Wanting heat and not getting it? Maybe this valve. Wanting cool and not getting it? Won't be this valve, check other things.

 

The inverter is brought up because many times the first symptom of a failed inverter coolant pump is loss of A/C compressor function.

Posted via the PriusChat mobile app.

 

What you've said about the inverter coolant pump and shedding the A/C compressor is simultaneously (a) true, and (b) not an explanation of why PriusCamper would write "your engine, heater and inverter coolant is a different system than your AC".

I questioned the way that was written, because that makes it sound like "engine, heater and inverter coolant" are one system, when they aren't; the engine and heater are one coolant system, and the inverter coolant system is a separate one.

And of course, as you point out, neither one can be completely ignored in an HVAC issue. The engine, and its cooling system (and therefore the control valve) are directly the source of heat the HVAC uses. The involvement of the inverter cooling system is less direct, but the inverter, which supplies the electrical power to run the A/C compressor, does need to be cooled.

 

The coolant control valve affects coolant which goes through the gas motor and the heater core. Call it loop 1.

The inverter pump affects coolant which goes through the inverter and (I think) the transaxle. Call it loop 2.

Loop 1 and Loop 2 are entirely separate. (They use the same type of fluid though.)

If the pump in loop 2 fails, or something else impedes the flow, and the inverter starts to overheat the car will shut off the A/C to reduce the thermal load on the inverter.

I am not too sure about the following. If the hoses are reattached to the coolant control valve incorrectly something bad happens, but as I recall, it shouldn't affect the A/C's ability to make cold air.

The A/C problem may have nothing whatsoever to do with loop 1 and 2. It may just be that there is an intermittent problem elsewhere in the A/C system. If the loss of A/C is related to a failure in loop 2 you should see elevated temperatures at the inverter. I have never done this myself, but if you were to aim an IR thermometer at the metal case of the inverter while the car is running, when the inverter is overheating I would guess that it would be very hot. Over 150F (?) would suggest a problem in that loop. Note that those high temperatures might be below the threshold for throwing a code.

 

The control valve in loop 1 has a position where it cuts off flow to the heater core. So if it gets stuck in that position, it can cut off the ability to make hot air when hot air is wanted. But that's the opposite problem from this thread, which is about getting hot air when hot air is not wanted, and the valve won't be the culprit for that.

 

This is the one thing you said that makes sense to me...

 

Oh good. What "the term" was in that sentence was "A/C", as seen in the part you ...ed out:

So if we agree that it's worth trying to make our posts clear and helpful to people who might be using "A/C" in any of those different ways, it's a good day.

 

Please tell us more about this OBD2 code reader that you're using, as it may not be up to the task. And are there lights on the dash?

 

We definitely will never agree on that. I know plenty of people on here that are unwittingly unclear and unhelpful to people.

 

Maybe it would be an easier lift to just agree some kinds of sleight-of-hand quote editing just aren't cool, ever, between people who are honest.

 

Do mean cool like coolant? Or cool like AC?

 

Or as in "not uncool."

Which in a Boolean sense doesn't tell you anything new, but in a linguistic sense kind of does, because 'uncool' has a narrower range of meanings than 'cool' has.