Hello all

I dont remember the specifics unfortunately of how this was diagnosed, so here it is.

In hot weather the AC essentially freezes up after hard usages of about 3 to 5 hours in driving. The main symptom is that air just starts to come out the vents slower and slower till it comes to a stop. I forgot the specifics of how that happens, but I believe it had something to do with a compression switch or valve that gets frozen and stops the flow of coolant. A possible fix to this was seeing if I could get the AC charged some just to see if it needs that. It was also speculated that this specific valve or item needs to have the entire AC system drained in order to get to, but perhaps there is a way around that> To my annoyance the car seems to require special coolant and unusually high pressures, unless perhaps you can getaway with regular AC coolant at the parts store?

 

Low refrigerant is the #1 cause of a frozen evaporator, particularly after a long period of lower utilization, i.e., you get the car cooled off, and it's just maintaining the interior temperature at a lower blower level on recirculation. If you switch to fresh air intake, it likely won't freeze because the air blowing over the evaporator is warmer and won't permit freezing.

HCH2 uses standard R-134a refrigerant. Absolutely nothing special there; however, it does use a special compressor oil that has extremely low conductivity due to the electric motor portion of the hybrid compressor being bathed in the refrigerant and oil. However, you can buy a $15 low side hose, and a $5 can of PURE R-134a (no oils, seals, dyes or other additives) and top it off using the sight glass and low side pressure gauge on the $15 hose. It's important to do it in about 90°F weather after the A/C has been running full blast for about 5 minutes.

 

Switching to outer air intake has it last longer, but it will still freeze, usually after a 3 to 5hr drive. I am of course talking about 90 + degrees F weather, usually with high humidity. I will check it after a long drive to see where the AC coolant pressure will be at and add if it needs it. So I have a can of coolant already, but its not pure and has additives and such, but has a reusable disposer. When twisting that off, is it normal to hear that hiss, or can I only take it off when the can is empty? Its only a dispenser for the low pressure coolant valve, so what pressure should I be looking after that long drive?

 

Typical dispensers puncture the can and will vent the entire can if you remove it.

Best to have two dispensers to avoid contamination: 1) for traditional A/C systems and 2) for hybrid-electric A/C systems.

I have two sets of full manifold gauges for precise work and two low-side hose dispensers for quick-fills. I recommend you get another dispenser and use it ONLY on the HCH.

 

Great Info, there must be something unique about an automotive electric AC compressor? The majority of Residential and Commercial HVAC cooling and refrigeration system compressors have internal electric motors that are oil and refrigerant bath cooled constantly. I am doing some research today as I have on my list to check the refrigerant level on a 09 Tahoe Hybrid system to make sure it is at peak performance for the summer season. Having a bit of trouble with the sites search feature today.......................

 

How many residential and commercial HVAC systems use R-134a and PAG oil? Zero? Yep. Zero. We're talking about automotive A/C systems not residential/commercial. Standard PAG oil has 10X the conductivity of the "hybrid specific" oil. Toyota spec for resistance is > 10MΩ. PAG is 1MΩ.

 

Since you brought it up R134A is actually very common outside of Automotive. If you take a close look most likely you have a household appliance Refrigerator/DeHumidifier/Window AC etc that uses R134A as the refrigerant. Carrier manufactured a HVAC that utilized this refrigerant.

This special low conductivity refrigerant oil must be a safety issue with the way these vehicles electrical systems works?
On a stationary system I guess if a short happens it goes to ground (no harm no foul, except your pocketbook to replace it LOL), Now on a vehicle, could a person stepping out of a vehicle become a source to ground with a shorted AC compressor? These things could be rolling Death MACHINES....................Just wait till Hollywood gets it hands on this material.
Could start seeing scenes where the car is rigged to electrocute the hero, but instead his wife or his concubine uses his car and is fried to a crisp and it all looks like an accident. The Plot Thickens.

 

Im not certain about residential usage of coolant, but perhaps it would be more proactive to go for a version of r134a that is for hybrids. Maybe this can? http://rechargeac.com/content/hyb-13...hicles?lid=468

This one is oil specifically for honda: https://www.hondapartsdirect.com/oem...BoCgo0QAvD_BwE

It would of course be easier to just add the pure 134a, however that said, is there a way to measure what the oil level is in the a/c?

 

If you read the product information, you will see that it's not specifically for hybrids ("For use on ALL A/C compressors (belt-driven, electric, and “Mechanical/Electrical Combination” units)"). The only difference between that product and straight R-134a is the label and likely the price.

No. There is no way to measure the oil level. The only way to ensure you have the proper amount of oil is to completely drain/purge the system and add the manufacturer's specified amount of oil to each component and then recharge. For example, Honda's instructions on replacing the compressor is to drain the oil out of the old compressor and add that amount of fresh oil to the new compressor.

 

I see, well thank you so much for your help.