Ac issue

[ltd02]

29" Hg = 20,000 microns This is not a deep vacuum. You should get below 750 microns which is 29.89" Hg. 500 microns is better.

You need a micron gauge to properly measure a deep vacuum. A compound gauge is not adequate. As you can see one inch Hg is over 20,000 microns.

Okay now I've really got it. Thanks! Micron refers to micrometer of mercury. Just found a nice table too:

Vacuum Pressure - Converting Units

 

[adamkrz]

29" Hg = 20,000 microns This is not a deep vacuum. You should get below 750 microns which is 29.89" Hg. 500 microns is better.

You need a micron gauge to properly measure a deep vacuum. A compound gauge is not adequate. As you can see one inch Hg is over 20,000 microns.

Your correct, I usually get my low side to 29.9" vacuum - I retired from the HVAC Field more than 15 years ago, I still use a Dial A Charge for charging small systems, I need to purchase a micron gauge.

 

[tom0826]

Referring to the original post, I too had these symptoms of marginal AC at idle and as megatone indicated, had the hissing sound when the car was turned off.

I wanted to see if I could top off the refrigerant and put some gauges on it, so I evacuated for an hour with my Robinair vacuum pump, then charged the system starting in vacuum, and on a 90 degree June day in SoCal, I had a low side of 75 and high side of 250. Similar to the OP, my low side pressure was rising as rpms rose, which indicated internal compressor leakage. I never did get adequate vent temperatures unless rpms were higher even with the fresh charge. I think I saw a best idle vent temperature of 80 degs in an open garage on that 90 degree day.

Nonetheless, I ordered a kit from rockauto that included a new Chinese made compressor with correct amount of oil, a receiver-dryer, seal kit, and a hose (that I didn't use) for less than 200 bucks shipped. I took it all apart and installed the new stuff the next weekend. The compressor is a bit noisy, but the system is working great. I now have the center vent temp at 50 at idle, recirculating and full fan. On road driving vent temp is 40 degrees.

Anyways, I hope this helps since we seem to have had the exact same problem.

Hints: Press metal gaskets on with correct size diameter socket prior to installing O-ring. Tip your old compressor and use the oil to lube the O-rings when you install. And get a temperature gauge - it looks like a small bbq meat probe. Cheap and critical to have.

 

[tjkj2002]

Referring to the original post, I too had these symptoms of marginal AC at idle and as megatone indicated, had the hissing sound when the car was turned off.

I wanted to see if I could top off the refrigerant and put some gauges on it, so I evacuated for an hour with my Robinair vacuum pump, then charged the system starting in vacuum, and on a 90 degree June day in SoCal, I had a low side of 75 and high side of 250. Similar to the OP, my low side pressure was rising as rpms rose, which indicated internal compressor leakage. I never did get adequate vent temperatures unless rpms were higher even with the fresh charge. I think I saw a best idle vent temperature of 80 degs in an open garage on that 90 degree day.

Nonetheless, I ordered a kit from rockauto that included a new Chinese made compressor with correct amount of oil, a receiver-dryer, seal kit, and a hose (that I didn't use) for less than 200 bucks shipped. I took it all apart and installed the new stuff the next weekend. The compressor is a bit noisy, but the system is working great. I now have the center vent temp at 50 at idle, recirculating and full fan. On road driving vent temp is 40 degrees.

Anyways, I hope this helps since we seem to have had the exact same problem.

Hints: Press metal gaskets on with correct size diameter socket prior to installing O-ring. Tip your old compressor and use the oil to lube the O-rings when you install. And get a temperature gauge - it looks like a small bbq meat probe. Cheap and critical to have.

That hose has the orifice tube in it,2nd mistake is "Chinese" made compressor.That noise is a failure waiting to happen,the compressor has already failed if making noise.

 

[nlocascio]

Got the jeep back and its all fixed. They had a master tech check it over. Said every thing tested out good. High and low side are OK, compressor is OK and did a leak test with dye, no leaks. Was half a pound down. Works good now.

 

[tom0826]

That hose has the orifice tube in it,2nd mistake is "Chinese" made compressor.That noise is a failure waiting to happen,the compressor has already failed if making noise.

Thanks tjkj2002 for giving me a heads-up on my mistakes. It could be that imminent failure is around the corner and I just don't know it.
You seem to be a great source for AC knowledge. What are the signs of a bad orifice tube? I did not change the hose with the orifice tube in it because there were no signs of leaks or freezing of lines, and the system was clean without contamination. The system held vacuum as well. I guess I should have changed the hose since it came with the kit, but I was too lazy. Should I still change the hose if it's made in China? Or keep the original OEM if it's in good shape? Or should I spring for a NEW OEM hose? Wondering what an AC pro would have done.

I guess I should re-do it again with a new Sanden? I don't mind doing it again since I have recovery equipment I can use, and I do a lot of residential HVAC, so I know just a little bit. All other affordable replacements seem to be Chinese made as well. Please share your experience and source for AC compressors. Are the Sanden compressors supposed to be noise-free? The OEM it came with on the Libby certainly wasn't and would love to have a noise-free mobile AC system.

 

[dougmac]

Thanks tjkj2002 for giving me a heads-up on my mistakes. It could be that imminent failure is around the corner and I just don't know it.
You seem to be a great source for AC knowledge. What are the signs of a bad orifice tube? I did not change the hose with the orifice tube in it because there were no signs of leaks or freezing of lines, and the system was clean without contamination. The system held vacuum as well. I guess I should have changed the hose since it came with the kit, but I was too lazy. Should I still change the hose if it's made in China? Or keep the original OEM if it's in good shape? Or should I spring for a NEW OEM hose? Wondering what an AC pro would have done.

I guess I should re-do it again with a new Sanden? I don't mind doing it again since I have recovery equipment I can use, and I do a lot of residential HVAC, so I know just a little bit. All other affordable replacements seem to be Chinese made as well. Please share your experience and source for AC compressors. Are the Sanden compressors supposed to be noise-free? The OEM it came with on the Libby certainly wasn't and would love to have a noise-free mobile AC system.

The only thing that I have seen go wrong with an orifice tube is plugging due to debris from a failed compressor. A restriction there will cause low suction pressure and a warm evaporator. If your suction pressure is good and your suction line into the compressor is cool, your orifice tube is doing its job.

Is your only concern the noisy compressor? Is the suction line cool at the compressor?

 

[tom0826]

tjkj2002 had me worried about the compressor. It's only slightly noisier than the oem ...not a bad noisy, like a slight gurgling sound when the clutch engages and the compressor is running. A friend used this brand kit on his honda crv and it's been solid for 2 years so far and is a little noisier than oem as well. I always knew compressors to make some noise when running and can attribute the difference in noise for different materials used internally or differences in wall thickness of components for the aftermarket part, but this is my assumption.
I just got the impression that I made mistakes and that failure is around the corner and wanted some clarification.

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[tom0826]

Yes. The suction line is cool and I have great performance. Just a slight more gurgling noise from the compressor.

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[dougmac]

I can't hear it, but... if its only slightly louder, i don't know if I would worry much..

 

[M38 Bob]

I would have sworn I detected a bit of sarcasm a post or two back. Funny how that works on forums sometimes.


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