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A/C Charging: In Progress...

 
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ColtHero
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2002 Chevrolet Impala


PostPosted: Sun Jun 19, 2011 6:27 pm    Post subject:  A/C Charging: In Progress... Reply with quote

A/C Charging: In Progress...

'02 Impala 3.4L 150k miles

It's 94 degrees here with 45% humidity.

Static Pressures before running engine first time: 98 psi (L), 90 psi (H). After running engine first time: 110, 105

Running Pressure (prior to charging) @ idle: 31..34 (L), 145..195 (H). Vent temp off the charts HOT.

AFTER charging 1 full (10 oz?) can: 35..51 (L), 195..240 (H). Vent temp down to 60F.

QUESTION IS:
----------
Documentation I've read says R134a HIGH side should top out at about 2.2 to 2.5 times ambient. At 94F, that's a range of 206F to 235F. I'm already maxing out at 240F on the high side after one can. But my vent temp is only 60F.

Are the 2.2 and 2.5 numbers correct? Can I actually (and safely) go higher on the HIGH side ... say 250-260 ... or whatever it takes to get the vent temp down to, say, 50F?? 60F is not that cold for a vent temp. I don't want to overcharge it, of course ... and I don't want any explosions either ...

I did this last April when ambient temps were at least 10 degrees lower and I was able to achieve a vent temp of under 50 degrees! I know I have a leak somewhere and I hope to find it this time around with residual dye from last year (this year's stuff doesn't contain any dye).
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MISHNAH
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2002 Chevrolet Impala
2006 Mercedes-Benz E Class
2006 Nissan Murano
2003 BMW 5 Series


PostPosted: Sun Jun 19, 2011 7:26 pm    Post subject:   Reply with quote

Was the system completely empty of refrigerant?

If it was, you'll have to add 3 full 12oz cans in order to have a "full" charge. You can have high pressures even when you're low.

Here are the pressures from the Service Manual.

Ambient Air Temperature
Relative Humidity
Service Port Pressure- Low Side
Service Port Pressure-High Side
Maximum Left Center Discharge Air Temperature


13-18C (55-65F)
0-100%
175-243 kPa (25-35 psi)
640-990 kPa (93-144 psi)
12C (53.6F)

19-24C (66-75F)
Below 40%
175-256 kPa (25-37 psi)
750-1120 kPa (109-163 psi)
12C (53.6F)

Above 40%
184-287 kPa (27-42 psi)
820-1240 kPa (119-180 psi)
15C (59F)

25-29C (76-85F)
Below 35%
196-277 kPa (28-40 psi)
960-1280 kPa (139-186 psi)
14C (57.2F)

35-60%
212-290 kPa (31-42 psi)
1020-1340 kPa (148-195 psi)
16C (60.8F)

Above 60%
223-316 kPa (32-46 psi)
1070-1460 kPa (155-212 psi)
18C (64.4F)

30-35C (86-95F)
Below 30%
220-303 kPa (32-44 psi)
1130-1480 kPa (164-215 psi)
17C (62.6F)

30-50%
223-322 kPa (34-47 psi)
1190-1570 kPa (173-228 psi)
19C (66.2F)

Above 50%
250-350 kPa (36-51 psi)
1260-1710 kPa (183-248 psi)
21C (69.8F)

36-41C (96-105F)
Below 20%
245-324 kPa (36-47 psi)
1300-1630 kPa (189-237 psi)
19C (66.2F)

20-40%
254-344 kPa (37-50 psi)
1350-1750 kPa (196-254 psi)
21C (69.8F)

Above 40%
273-364 kPa (40-53 psi)
1440-1860 kPa (209-270 psi)
23C (73.4F)

42-46C (106-115F)
Below 20%
273-348 kPa (40-51 psi)
1440-1860 kPa (209-270 psi)
22C (71.6F)

Above 20%
284-370 kPa (41-54 psi)
1550-1930 kPa (218-261 psi)
24C (75.2F)

47-49C (116-120F)
Below 30%
308-374 kPa (45-54 psi)
1720-1970 kPa (250-286 psi)
24C (75.2F)

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2002 Galaxy Silver Sedan - LS cluster - Debadged - Intrigue compass/autodim mirror - DIC - Regal graphite leather seats - LS console with floor shift conversion - Monte Carlo black leather steering wheel - LS springs - KYB GR-2 Struts - GMPP sway bars and rear STB - Fog light frontend harness - LS Bumper with fog lights - Painted trim and side skirts

2006 Nissan Murano - Autodim/compass mirror
2006 Mercedez-Benz E350 - Stock for stock, its faster than an SS, woot!
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ColtHero
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2002 Chevrolet Impala


PostPosted: Sun Jun 19, 2011 7:38 pm    Post subject:   Reply with quote

MISHNAH,

I used the 96F-105F and 20-40% H ranges and charged a 2nd can. Ended up with a vent temp of 49-50F and LOW and HIGH side readings in the ranges you gave.

However, the gauges really don't move much at all. Last year I remember the gauges moving up and down like clockwork. Now they move a LITTLE, but are mostly static. That's not good, is it? Could that be an indication of a compressor problem? But I'm getting pretty cold air, so what's up? Is this going to be short-lived (regardless of the leak)? Last year the cold air lasted the entire hot-weather season. I hope this lasts at least as long as it takes me to find the leak.
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MISHNAH
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2002 Chevrolet Impala
2006 Mercedes-Benz E Class
2006 Nissan Murano
2003 BMW 5 Series


PostPosted: Sun Jun 19, 2011 8:29 pm    Post subject:   Reply with quote

Do you mean, the gauges moving while the a/c is on? They should be mostly stable, with the only fluctuations being when the a/c compressor turns on and off.

I just replaced my entire a/c system short of the evaporator Rolling Eyes Once it was charged, gauges were basically stable, only moving when the a/c comp cycled or I revved the engine.

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2002 Galaxy Silver Sedan - LS cluster - Debadged - Intrigue compass/autodim mirror - DIC - Regal graphite leather seats - LS console with floor shift conversion - Monte Carlo black leather steering wheel - LS springs - KYB GR-2 Struts - GMPP sway bars and rear STB - Fog light frontend harness - LS Bumper with fog lights - Painted trim and side skirts

2006 Nissan Murano - Autodim/compass mirror
2006 Mercedez-Benz E350 - Stock for stock, its faster than an SS, woot!
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ColtHero
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2002 Chevrolet Impala


PostPosted: Sun Jun 19, 2011 10:53 pm    Post subject:   Reply with quote

Yeah - while the A/C is ON, the gauges don't seem to move much at all. I guess that's normal? This car has manual A/C, so that means the compressor will always stay ON ... because that's what appears to be the case - it's always spinning.

I guess what I'm remembering last year was the compressor on my other car ('97 Taurus) cycling ON and OFF because it was low on refrigerant (and the gauges fluctuating up and down with that cycling).

I just checked my notes from last year ... I had achieved 42-43F vent temps with the Impala. After the 2nd can (THIS time), I ended up at a LOW side high of 42 psi and a HIGH side high of 232 (with vent temp of 49-50F). My final STATIC pressure ended up at 80 psi on both LOW and HIGH side gauges (if that means anything).

Almost seems like it might be able to take a little more, but I'm going to drive it first and see how it performs at road speed.

Thanks for now!
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MISHNAH
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2002 Chevrolet Impala
2006 Mercedes-Benz E Class
2006 Nissan Murano
2003 BMW 5 Series


PostPosted: Sun Jun 19, 2011 11:53 pm    Post subject:   Reply with quote

Was the system completely empty?

If all the refrigerant had leaked out, you will need to add 3 12oz cans for a full charge. If there was some left over in the system, then you have to play with the gauges and try to judge when its the right pressure. Beware that adding more refrigerant does not always correlate to a big increase in pressures. The difference between 1 can and 3 cans for me was only about 10 psi on the low side and maybe 40 psi on the high side.

What you are calling static pressure is the pressure in the system when the compressor is not running. While this would tell you how much is in the system, there is no spec for this pressure, so its basically worthless. I think mine was around 80-90 psi last time I checked.

The orifice tube acts as a restrictor, so your high side will always be much higher than the low side.

With orifice tube systems, the compressor tries to build up pressure on the high side (behind the orifce tube), then the a/c pressure switch will cut off the compressor until the pressure bleeds off, then restarts the compressor to rebuild pressure. This goes on over and over and over and is perfectly normal.

I'm not 100% sure, but I believe that the compressor running constantly means the system is low, and cant maintain a high enough pressure to let it cycle off. A properly charged system should be able to cycle off periodically while still maintaining the proper temperature.

My compressor is currently on most of the time, might need to give it a little more charge, just dont have the gauges right now lol.

_________________
2002 Galaxy Silver Sedan - LS cluster - Debadged - Intrigue compass/autodim mirror - DIC - Regal graphite leather seats - LS console with floor shift conversion - Monte Carlo black leather steering wheel - LS springs - KYB GR-2 Struts - GMPP sway bars and rear STB - Fog light frontend harness - LS Bumper with fog lights - Painted trim and side skirts

2006 Nissan Murano - Autodim/compass mirror
2006 Mercedez-Benz E350 - Stock for stock, its faster than an SS, woot!
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ColtHero
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2002 Chevrolet Impala


PostPosted: Mon Jun 20, 2011 3:46 pm    Post subject:   Reply with quote

"Completely" empty? I don't know. My understanding of what I read in an article on A/C on the web was that the STATIC pressure told you whether you had ANY amount of refrigerant in the system. So, my guess is there was SOME refrigerant in there ... just not enough to provide any cooling (at all).

"Play with the gauges to try to judge when it's the right pressure". Yeah - that's what I'm sort of doing. I found a MasterCool document online that showed for an ambient temp of 95F I could have a LOW side of 50-55 psi and a HIGH side of 275-300 psi, so I charged the 2nd can and reached 49-50F vent temp (good enough). But my gauges didn't move much at all. I was expecting the pressures to diverge more with the HIGH side causing me some anxiety, but they didn't. And I'm sure the can(s) fully discharged because I had them sitting in hot tap water and they both sunk to the bottom initially then floated at the end ... and when i pulled them out (finally) they were clearly empty (although a tiny amount of gas DID leak out as I was disconnecting the tap ... but that probably happens all the time ... maybe you can never REALLY fully discharge EVERY BIT of gas in the can???)

I think you might be right about the compressor running all the time as an indication the system might still be low. But I don't really care because the next order of business will be to see if I can find the leak. If I don't see anything with the black light I may buy one of those ONE-SHOT (LOW SIDE) cans that shoot dye into the system. I'm hoping remnants of last year's dye still remain, but maybe not.

Also, does this car's system HAVE an orifice tube? Reason I ask is someone here mentioned to me that it could be possible moisture in the system is freezing blocking this off. Obviously it's not blocked, but maybe it's further obstructed? Probably no fix for this short of evacuating the entire system, vacuuming, and re-charging. But I'll only do THAT if I can find and fix the leak first! It MAY only be a port leak (Schrader valve). I think that's the problem with my Taurus. I KNOW the HIGH side valve on that car is leaking! I'm going to try slightly tightening it with one of those thumb tools first. If that fails, I'm going to buy that specialty tool that can replace the core without evacuating the entire system - but only if the black light says this is the only source of leakage...
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