AC Cold then warm - Restart Cold again - Solve the Mystery

2004 Prius over 200K miles but many thousand idle hours (Prius Camper)

Just did another evac and recharge and no change, was low only by a very small amount over a long period of time since the last one.

Especially in temps over 90 in hot humid heat

It will blow cold. Lowest measured at 55 degrees F.
Parked in shade in can run a long time blowing cold
Have to keep on Max cold or maybe up to 69 otherwise it may start blowing warm

If I turn car off and right back on Cold again unless it is real hot might have to wait a bit

Coolants in inverter and engine at correct levels and flowing.
New dual fans blowing correctly in the right direction

Compressor was checked out as good by Toyota
They replaced air mix servo door which did nothing $$$$$ (5 visits no solution)

Many dye checks show no leaks and will have it checked again after lastest evac/recharge

They used separate machine and the correct oil.

Code B1476 persists

Open circulation switch only works on floor or defrost setting I noticed

Suspect controller for air servo door, engine running hot but no warning light, faulty compressor auto cut off switch

Mystery. Sometimes will blow cold even driving above 90 degrees or get less cold then colder again but once it goes warm there is no coming back.

I turn off ac compressor through touch screen while driving thinking that may reset it but never works

So have to wait until stop light and shut car off and back on and it will blow cold again unless it is very hot but sometimes even if it is very hot outside.

The closest consistent pattern is driving when very hot it is most likely to start blowing warm even if accelerating slowly.

Other pattern even if parked in shade which ac will blow cold 55-60 degrees for a long time but if you start moving the temp up to above 70 it will likely start blowing warm air unless I catch it fast and move back to max cold otherwise have to stop and start car again to reset to blow cold air again.

If really hot parked in shade it will blow cold along time if leave on max cold but may eventually start blowing warm air after a long time like over an hour or more but not always.

Want to monitor engine heat to see if heat correlates with AC going out through some obd to phone app maybe

I can feel the heat coming from the engine is rather hot more than I noticed before ever as the original owner but that is subjective.

No warning light has ever gone off for overheating but don't trust those warning lights as I had a noisy bad brake acuator that lasted months before the lights finally flashed and code was generated which I needed to be covered under extended warranty which may point to electrical problems I am guessing.

If engine temps are within normal limits I am tempted to try a used or refurbished oem compressor as I have read reports of non-oem ac compressors may not be compatible as advertised but not sure.

I saw no reports of problems with my Oreilly's Import Direct compressor.

Was going to use some radiator cleaning solvent sprayed on and let soak and hose off gently to see if that would help keep engine a little cooler and see if that would possibly have a positive effect on the engine heat causing the AC Compressor to indirectly stop blowing cold air.

The inverter coolant reservoir shows turbulence.

One person did experiment doing the same on the condensor and prooved it did increase the efficiencies in ac low high side pressures not in a Prius though.

Obviously I am no expert but I am persistent in looking for patterns and reading.

I've consulted several shops and they talked of thousands of dollars possibly of diagnostics and labor and replacements. The car's value now is appx $3000 and probably less with this AC problem and already have put in about $1300 into this problem.

One shop that actually listened to my patterns and history and sounded like he knew what he was talking about thought maybe it was electrical and maybe ECU module could be the issue

Wondering what is making it blow cold again when I stop a restart car but not when I just turn ac off and back on again.

Any detectives out there that know more than me (which isn't much) feel free to give me any theory or what would you check or do. Thanks in advance for reading this far.

 

I actually had to have my inverter pump replaced not to long ago. I think it may have had a positive effect on the problem. Hybrid assistant free app will show inverter and ICE coolant temps as well as HV battery temps plus turn on fan to max speed.

The fault code using the on screen AC fault code check (see YT) was 76 with B14 being the prefix. I made the mistake of putting an after market AC compressor on my Prius. It blows cold but may go out with that fault code. You can find Toyota documentation on this fault code and possible repairs. I had replaced the dual fans as they were getting loud from over use (Prius Camper) and probably not very efficient. I'm missing those shrouds over that area due to poor shops not replacing them and not noticing for a long time. My ambient temp sensor goes up in the hot Summer higher than actual temp but that may be the hot asphalt road. I could replace that easy to see if improper temp is giving controller poor feedback but T-Lech didn't think so. (AC Genius). I have become better at driving to prevent AC going out by accelerating slowly avoiding high RPM's anticipating the traffic flow like hyper milers. Could be pressure switch but no code for that.

Being the original owner of the 2004 Prius my experience at least in mine is conditions can exists long before the code shows as even pending but B1476 is pretty consistent. Find the method to check your AC fault codes on screen on YT and might as well check 12v battery too you can do on screen. I have to look it up each time.
Disconnect you 12v Battery through the connectors (on YT too) for 10 minutes to clear code(s) and see if it comes back. I had my AC serviced a number of times and analyzed for leaks, cross contamination and the puffer test for evaporator leaks. I believe T-Lech says people should do this at least every 2 years and if they don't the result is a burned out AC compressor as refrigerant or what ever it's called does get low slowly over time and notoriously neglected. I was lucky mine lasted so long but sooner or later it will burn out if not serviced properly with a proper hybrid machine and tests with full evac, weighing and recharging according to specs. T-Lech says the bubble window viewer method is unreliable.

I was and maybe still will have the AC compressor replaced but nursing it along and may try some of those other things even engine coolant pump. Maybe the fans need to be OEM. Need to check into that but they are quiet now and seem to be working. I believe this after market AC compressor is not communicating as well as OEM. I can run in park cold for a long time and it won't go out unless I move the temp up over 67.

I couldn't find any complaints on this Oreillys AC Compressor online which makes me scratch my head.

It is hot here in coastal southeast so I start car in the shade max cool closed circ and let it cool down well then drive like grandpa to the store and many times even at 93 and very humid I make it there and back but sometimes it may go out due to traffic flow or whatever so at a red light I'll do a quick stop and start of car.

I'll leave car running and lock with manual key while I go in the store.

Last thing before shut down I will turn fan speed all the way down and choose open circ which for me is defrost setting or floor (another controller issue... can't do open circ at the straight chest level setting and then I turn off AC on the display. It seems to help the compressor start better that way the next start.

I start car, then go to climate control with fan speed at 1 and hit AC then listen for compressor start then gradually move up the fan speed manually then switch to chest level setting. I have my windows open to let hot air escape. I'm in the shade as well. If some where else and didn't leave the AC on I may need to find a shade spot to restart car and let it cool for a few minutes.

Seems like a lot but I've become use to it. I reframe it into a game like hypermilers except my motivation is not to roast lol . Either my prayers are being answered or I'm getting better at this.

Still have August the brutal month to go. I want to make 20 years next year of owning this car and maybe more. Other than that the car works fine. It does better on the Interstate maybe because the air flow. No leaks in the condensor or evaporator. Hope all that helps. Check out T-Lech's YT channel plus he's on PC.

Also get a temp gauge for AC outlet and check close circ max cool lowest fan speed and just look for patterns over time and get AC properly serviced and checked out by someone that knows what they are doing and has a hybrid machine to avoid cross contamination and can check for it.

I did read one hybrid school ran an experiment putting the wrong refrigerant in it on purpose and the Prius kept running with no problems but they took the article down so it may have developed electrical problems. They were marketing some service to flush the system if there was cross contamination if I remember correctly so maybe the article wasn't helping their marketing. StillI trust it is a must to use the non-conductive refrigerant.

Let me know what you find out.

 

Correction: On that story of using the wrong refrigerant it was actually the wrong oil (PAG) not the non-conductive oil.

 

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I'd get in touch with T-Lech here or YT to get an real expert opinion with all details.