Any Auto AC Mechanics Here?

2003 Suzuki Aerio SX
290,000 miles. Bought her new. Her name is Suzy.

AC no cold when weather is cool about 70° Spring and Fall weather. Works great in hot summer weather. Today we had global warming, outdoor temperature got to about 80°. AC started working.

When AC not working, 70° Spring and Fall weather. - Press AC button. It lights up green. Right plastic radiator fan starts spinning. Center of AC compressor no spin.

When AC is working, 80° hot summer weather. - Press AC button. It lights up green. Right plastic radiator fan starts spinning. Center of AC compressor spins. Few seconds later, left plastic radiator fan starts spinning.

Problem first happened last spring when weather was cool about 70°. Happening again now that fall is here and weather is getting cooler about 70°.

Have you ever had it topped up with gas? In the cooler weather the pressure may be dropping and the HPLP switch may be inhibiting the pump. That would be my first check.

Then I would look for info to locate and test the outside ambient temp sensor. If that's faulty and reading wrong the climate control may not be starting the pump because it thinks it's far colder outside than it actually is.

Coolohm said:

Have you ever had it topped up with gas?

Click to expand...

Last fall. One year ago. AC no cold. Before that never touched the AC since car was new in 2003.I have very little experience working on auto AC. Bought 2 cans R-134a and a yellow hose. Added 1 can R-134a following instructions that came with the yellow hose. Compressor came on and AC was cold. If one can is good, two would be better? WRONG! Added second can. AC no longer cold. Compressor clicking on then off and sounds like its freaking out. PANIC and call a real mechanic. He tells me what I already know. I am a idiot. He explain how to let some refrigerant out like you let air out of a tire. Let some refrigerant out ---- hiss. Compressor sounds somewhat normal and AC is cold. Now I am not sure if there is correct amount of refrigerant? Leave car at mechanic's house so he can take it to his work at a new car dealer. Not exactly sure what he did? Empty then refill Freon? He did not charge that much.
Please see pictures.
View attachment 1

Yesterday I took it to a auto parts store. Auto part guy put a gauge on the same fitting where ya add refrigerant. Gauge showed red as in pressure too high.

I have a service manual.

Yep. pressure's too high now. buy a gauge. let more out until you're in the green.

What AC gauge should I buy? I like good quality tools.

No one answer my question. Ask at auto parts shop What AC gauge should I buy? Auto parts guy chose this one.

http://www.fjcinc.com/?product_info=r134a-brass-manifold-with-72-hoses-quick-couplers-boxed
6715B – R134a Brass Manifold with 72″ Hoses – Quick Couplers – BOXED

Got it. Got some learning to do.

My shade tree trick to determine if an AC system is undercharged is blocking some air flow from a portion of the condenser coil. If the evaporator air goes colder while some of the “capacity” has been reduced then it can probably use a little more Freon.

I learned this by accident on my home AC. Early one spring we had a warm spell, cranked the AC on and house cooled down fine. Month later (after mowing the yard and trimming grass away from the condenser coil) the system wouldn’t get cold. It was low on Freon.

Reason it got cold early Spring was because enough grass had grown up and was blocking some of the air flow through the condenser coil. Once the grass had been trimmed and the full air flow across the condenser coil was restored the system didn't have quite enough Freon to cool for the "restored" system capacity.

I later learned some AC installers when forced to use a larger condenser for a system than what’s required, use sheet metal to block off condenser airflow to effectively reduce the capacity of the system.

Over the years I’ve used this trick (chunk of cardboard) on auto AC’s to help figure out if the system is low on Freon without a full evacuation and refill with the specified amount.

30 years ago it was easy to grab the evaporator inlet and outlet pipes from under the hood.
If the outlet was warmer than the inlet it was time to add more.

Bought FJC 6030 Can Tap

Can tap goes on center yellow hose.
Testing how blue, yellow, and red, hoses are connected by blowing in them.

Hook up gauges. Start car. Compressor seems to be going off and on too much. Look at chart in the service manual. Graph with pressures and ambient temperature. 50° according to dashboard temperature gauge. Guessing it was also about 50° in the shop with the doors open. Not sure if I should let refrigerant out of the low or high side? Let it out of the low side. My reasoning is that I put the refrigerant in the low side. Keep letting refrigerant out while watching the gauges. Compressor begins to run for a longer time. Here are PSI readings when I stopped letting refrigerant out.
Low Pressure Gauge 9 - 30
High Pressure Gauge 105 - 70
First number is with compressor running.
Second number is with compressor off.
Chart goes from 59° to 95°F. 50° is off the chart.
Never looked to see if center part of compressor to confirm that it was spinning. Did feel cold air at vents.

Hoping AC will be cold next summer. Have not driven car since letting refrigerant out.

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