How to improve the A/C Performance?

[Buzo]

My A/C works great when there is no direct sunlight. I'll say from 6:00 PM to 10:00 AM, but there is this period of time when the car is exposed to the sunlight where the max A/C is just not enough. I mentioned sunlight, because if it is cloudy, it works OK even in that timeframe.

I have a pressure 30 PSI in the low pressure side and 150-200 PSI in the high side, so I consider those normal.
Both fans kick in as soon as I press the A/C button too.

What else can I do to get cooler air during this period of time? When I actuallty need it the most?

Just as a sumary:
New Denso compressor
New hoses and manifold
New Dryer
New expansion valve. This one came with an extra port that I plugged off when installed it.
Cleaned the core inside the HVAC from all the debris.
Full-filled the system with r134A

I didn't do anything to the condenser in front of the car, Is it possible it can be internally plugged off? Can it be cleaned?

[2geeSEi]

Are those pressures at idle, or 1500 rpm? Also, what was the ambient temperature when you got those numbers?

[Jafir]

Did you pull vacuum before you recharged the system?

If you condensor is dirty or dinged up it will reduce efficiency.

The coldest 3G a/c I've had was on one that had been hit in the front and I replaced the condenser with a new aftermarket part and a used compressor. Pulled vacuum for a few hours and then filled it with duracool or freeze12, I cannot remember.

[Dr_Snooz]

What are your vent temps?

Honda A/C's never were especially good. If you live in a hot area like Texas or central California, they just can't keep up.

Here are some thoughts.
- Tint your windows
- Paint your car white (Seriously. It really helps)
- Park in the shade
- Use a sun shade or car cover when you park

[Buzo]

Outside temperature was 95 F when I measured the pressures & it was at idle speed. We just hit the 100's this week.
I did pull vacuum, but using the engine only. I'll say that it went from atmospheric 92 kPa down to 30 kPa for half an hour.
I haven't measured the vent temps recently, but when the A/C is into the "working hours" my passengers can't stand the max A/C. I usually need to select a lower fan speed.
But when it is not, the air coming out of the vents are certainly colder than if I had the A/C off, but not enough to make me feel comfortable. Only when I take off the temperature starts to cool down, until I get to the next red light.

[2geeSEi]

Under those parameters, your pressures are a bit low. Do you remember how many ounces of R134 you put in? For R12, the system holds 23-26 oz, which equals 21-23 oz R134. Your low side should be between 30-40 psi depending on humidity at 1500 rpm with the 95 F temp. Here is the temp/pressure chart:

http://i.imgur.com/wogU5mI.jpg

[Buzo]

Thanks for the chart. Just a plain sight, I am in the lower side of the correct pressures. I guess I need to repeat the measurements and use the proper idle speed of 1500 rpm. I also used to keep the doors and windows closed.

Sorry I didn't measured the quantity in oz. when I refilled the system. I used one 1kg can (35 oz.) and stopped filling when the low pressure side reached stability.
I know there was some gas remaining in the can but not sure how much.

Something to highlight is that it says "avoid direct sunlight during the test", so its clear it affects the performance.

One question though, Is anybody else experimenting the same in his car?

I live close to El Paso TX, its very hot & dry down here. We are at 100F today and we might reach 114 in the hottest days of the summer.

[2geeSEi]

You are in the lower side of the correct pressures, but at idle. Keep in mind that the compressor will pull the low side down as the rpm increases, so at 1500, it might be less than 25 psi.

[Dr_Snooz]

Those charts are for R12, BTW. I'm not sure how applicable they are going to be to a retrofitted 134 system.

Buzo, is your car an auto?

[2geeSEi]

Those charts are for R12, BTW. I'm not sure how applicable they are going to be to a retrofitted 134 system.

That is why it is best to charge by weight. 1.8 oz R134a = 2.0 oz R12a. The R134a pressures will be slightly higher than the R12a pressures. Here is a chart I found, but it is just a guideline: IDQ - Auto A/C Products & Sealing Solutions (http://www.idqusa.com/faqs.php?faq=74&faq_id=74&category_id=18) . I personally like the hydrocarbon refrigerants since the high side pressure is much lower.
I was noticing that you didn't mention anything about what oil you put in with the R134.

[Buzo]

Yes, my car is automatic. My Meqasquirt manages very well the automatic idle speed control and keeps it at 900 regardless of the load of the A/C compressor. I feel slight peaks in RPM during the engage/disengage of the clutch.

When I bought the compressor it was loaded with "R12 oil", then I turned it upside down to remove and measure the qty of oil and replaced with the same qty of R134a oil before installation in the car.

Still I have no explanation why the A/C works Ok if the car is moving, even at noon. Is it because the higher speed of the compressor or the air passing through the condenser, or both?

The contaiment action is to park the car in the shadow in front of a big wall at work. I'll recheck the pressures until the weekend, so I can do it at noon.

[2geeSEi]

When I bought the compressor it was loaded with "R12 oil", then I turned it upside down to remove and measure the qty of oil and replaced with the same qty of R134a oil before installation in the car.
You do know that the R134a will not circulate the R12 oil (mineral oil) that is in the system. You have to replace all the oil in the system, not just what is in the compressor. It is about 4 ounces. Also, PAG oil is not compatible with the mineral oil and turns to jelly. If you aren't flushing the whole system, you have to use POE (polyol ester) oil, which is compatible with R134 and doesn't react badly with the mineral oil.

[Dr_Snooz]

Well, I was going to say that if you have a stick, then just bump up your idle to compensate. Since you have an auto, that won't work.

My hunch is that your system is working just fine. It's real hard for these systems to keep up on the hottest days, especially when they are idling. If you take a look at the charts that 2GeeSEI posted, you'll see that on a 100 deg. day, a vent temp of 75 deg. is considered normal. That's simply not going to keep the car cool. And that assumes a new system, charged with R12, functioning optimally. Your performance with an old system, retrofitted with 134 can only be less than that. You will probably be best served by exploring alternative methods of improving comfort, like tinted windows, etc.

Definitely check what your vent temps are, but don't get your hopes up. I drive around with a meat thermometer stuck in my vents to let me know how I'm doing. Keep that chart in mind as you drive and if you just have to do something, consider using a hydrocarbon refrigerant. Most guys on here that use them like them.

[Legend_master]

Here is a theory that seems logical to me. I am going to try it.

Improve Car Air Conditioner Performance Without Additional Freon (DIY) (http://www.uniquestuff.net/improve_car_air_conditioner.html)

[2geeSEi]

Definitely check the pressures though. With R134, I would expect the high side to be in the upper 200's at 95 F. But like Dr_Snooze said, I would have gone with a hydrocarbon refrigerant. Lower head pressures, compatibility with all oils, efficiency as good or better than R12. With R134, your vent temps will never be as good as those in the charts.