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2010 Honda Pilot Touring AWD
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Has anyone experienced this and can help explain?

After the loud sound of pressure being released and smoke coming from the grill (and then AC only blowing warm air), the mechanic only found that the AC system passed a pressure test and just needed a recharge. All other systems checked ok. Now, it's running fine and AC blowing cold air.

It's 2010 with 170k miles -- so I just assumed the AC would need an overhaul.
 

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2020 Honda Passport Touring AWD Metallic Steel
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Sounds like the pressure release valve opened. Could be one of several issues. Bad high pressure sensor, bad valve or a failing compressor that is building up too much pressure. At this point it's probably best to just watch it and see what happens. Could have been a fluke but I doubt it. If there is an issue it will show its self again.
 

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I would replace the compressor relay just to be safe. Should cost about $8. There is a thread on the compressor relays failing so the compressor does not shut off even when AC not called for. That leads to the high pressure release you described.
 

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AC systems don't vent on a "fluke". Something drove the system pressure very high; Overcharge of refrigerant (very common), air in the system (common) AC/radiator fan wasn't spinning or spinning slow (less common), sticking expansion valve (uncommon). Air can enter when newbies buy recharge kits at Autozone and fail to bleed the hose before attaching to the car LOW pressure valve. "I'll just put a can in it", often overcharges. The compressor is the least likely culprit. A bad pressure sensor would not have been it. If the mechanic did a proper vacuum down and recharge, then that would have addressed any air or overcharge. You'll know before long whether it was the simple solution.
 
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2020 Honda Passport Touring AWD Metallic Steel
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AC systems don't vent on a "fluke". Something drove the system pressure very high; Overcharge of refrigerant (very common), air in the system (common) AC/radiator fan wasn't spinning or spinning slow (less common), sticking expansion valve (uncommon). Air can enter when newbies buy recharge kits at Autozone and fail to bleed the hose before attaching to the car LOW pressure valve. "I'll just put a can in it", often overcharges. The compressor is the least likely culprit. A bad pressure sensor would not have been it. If the mechanic did a proper vacuum down and recharge, then that would have addressed any air or overcharge. You'll know before long whether it was the simple solution.
Explain the no possibility of a fluke to Tony Stewart, July 2008 a decal disaster on the hood took him out of the race. Wind pealed it back. Not something that happens too often.

I remember seeing another NASCAR race where a driver had to pit for an exceptionally overheating vehicle. Radiator cap fine, radiator fine, hoses fine, amount of coolant fine. What wan't fine was the piece of paper that blew up from the track and attached itself to the radiator blocking off the air flow. The driver got back on the track but that FLUKE took him out of the race. AC systems also have a condenser up front along with a radiator. Well all except the few remain air cooled engines. No radiator.

The OP mentions nothing about adding any refrigerant and ac systems do not magically over charge. Could the OP have done this, yes, but we don't know. If failing expansion valves are so rare, why do several companies make replacement expansion valves.

That is why I suggested to the OP that they take the wait and see approach. Until the issue manifests itself again, if it does, then there is no real way of telling what caused it, especially since according to the OP the system passed a pressure test.
 

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Well, I suppose to make a profit would would be wise to sell repair parts primarily for non-flukes (like Greenlee, HP, Tektronics). A Walmart bag on the radiator, or one of your NASCAR examples (which weren't mystery problems), are "flukes" I'd agree. A dodgy expansion valve or sticking radiator fan relay, or a wonky compressor (wonky exactly how?) is in my observation, a less frequent "intermittent fault".
 
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