Question re minimum safe refrigerant amount.

[GJHANS]

The refrigerant in my CRV was recharged last week and the AC technician mentioned the AC system only contained 8 oz and required 18 oz.

At 8 oz the car was only at 45% full charge.

1. Is there a point where, if the vehicle's system falls below a certain percentage of full charge, it could cause the AC system to run inefficiently? If so, at approximately what percentage of full would that be?

2. Also, my understanding is that when a system's charge gets too low, the compressor in many vehicles will shut down as a "fail safe". Just curious if anyone knows what the percentage of full capacity that might be? (at which point the compressor would shut off)

Thanks!

[JohnHere]

The refrigerant in my CRV was recharged last week and the AC technician mentioned the AC system only contained 8 oz and required 18 oz.
At 8 oz the car was only at 45% full charge.

Yes, I recall that from your previous post. Was the compressor engaging at that point? Probably not is my guess.

1. Is there a point where, if the vehicle's system falls below a certain percentage of full charge, it could cause the AC system to run inefficiently? If so, at approximately what percentage of full would that be?

With your system, holding only 18 ounces of refrigerant, just a couple ounces short will begin to cause problems.

2. Also, my understanding is that when a system's charge gets too low, the compressor in many vehicles will shut down as a "fail safe". Just curious if anyone knows what the percentage of full capacity that might be? (at which point the compressor would shut off)

Offhand, I don't know what the percentages would be, but it normally depends on the high-side and low-side pressures as sensed by a pressure switch in the system. Below ~25 PSI on the low side, the compressor will shut off. And above ~404 PSI on the high side, the compressor will shut off.
Some Honda vehicles also have what's called a Thermal Switch that shuts-off the compressor if it gets too hot due to a low charge. Someone else asked about a Thermal Switch issue about a week or so ago.

Another concern is circulation of oil to the compressor. With a low refrigerant charge (and low pressures), the compressor will be starved for oil, compromising it's "health."

[GJHANS]

Thanks for your reply. The compressor was still engaging normally and the system was cooling well before the recharge. I'll try and make sure to have the system serviced on a more frequent basis. When it comes to AC systems, it seems more difficult to know when to bring it in. Some systems leak more refrigerant through the seals than others. I keep a thermostat in the center vent.

[Cusser]

It seems to me - and I'm NOT an AC professional - that manufacturers over the last couple of decades have gone to smaller driers, so that fewer ounces of refrigerant would be required, a cost savings. Given that, over or under such reduced ounces of refrigerant give poor performance.

I'm from the consumer products industry, and we had cost savings programs wit soap bars, packaging, etc. - such cost savings saved millions of dollars.

[JohnHere]

Thanks for your reply. The compressor was still engaging normally and the system was cooling well before the recharge. I'll try and make sure to have the system serviced on a more frequent basis. When it comes to AC systems, it seems more difficult to know when to bring it in. Some systems leak more refrigerant through the seals than others. I keep a thermostat in the center vent.

That's all good stuff.

I'm surprised that the system didn't shut-down the compressor at such a low refrigerant level.

If you like to tinker with your MVAC and keep it in tip-top shape, like I do, consider investing in a pro-grade Manifold Gauge Set, a heavy-duty rotary-vane vacuum pump, an accurate refrigerant scale, a digital thermometer to monitor center-vent temperatures (if you don't already have one), and a 30-pound cylinder of R-134a. Then you can do it yourself. Consult Tim at ACKits.com for the pro-grade equipment.

If you need to recover the refrigerant before opening the system and doing repairs, a local shop can handle that for you at a nominal fee.

The photo (sorry...the quality isn't the best) shows a digital thermometer that I place in each of my vehicles to keep tabs on the A/C systems.

[GJHANS]

Thanks for your reply. The compressor was still engaging normally and the system was cooling well before the recharge. I'll try and make sure to have the system serviced on a more frequent basis. When it comes to AC systems, it seems more difficult to know when to bring it in. Some systems leak more refrigerant through the seals than others. I keep a thermostat in the center vent.

That's all good stuff.

I'm surprised that the system didn't shut-down the compressor at such a low refrigerant level.

If you like to tinker with your MVAC and keep it in tip-top shape, like I do, consider investing in a pro-grade Manifold Gauge Set, a heavy-duty rotary-vane vacuum pump, an accurate refrigerant scale, a digital thermometer to monitor center-vent temperatures (if you don't already have one), and a 30-pound cylinder of R-134a. Then you can do it yourself. Consult Tim at ACKits.com for the pro-grade equipment.

If you need to recover the refrigerant before opening the system and doing repairs, a local shop can handle that for you at a nominal fee.

The photo (sorry...the quality isn't the best) shows a digital thermometer that I place in each of my vehicles to keep tabs on the A/C systems.

Thanks for the good ideas. The local Community College has an auto AC class, but only in the spring. I'll seriously consider taking it next year. It's free for seniors...

[JohnHere]

Thanks for the good ideas. The local Community College has an auto AC class, but only in the spring. I'll seriously consider taking it next year. It's free for seniors...

Good timing that the CC offers the class in the Spring, just when people start thinking about getting their MVAC systems in shape for the Summer. I, too, avail myself of some of those "free for seniors" offerings

[andrew vanis]

. I, too, avail myself of some of those "free for seniors" offerings

So where would one go to take a class that you would teach?

..... I'm thinking it might be worth a road trip?