If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
R134A help needed; 1998 Suburban.
I have a 1998 Suburban with the 5.7L V8 engine. My wife
has observed that the AC in this SUV is not quite as good as my 1995 Blazer AC with a 4.3L V6 engine (it does very well). I bought the Suburban used, and had a mechanic check/charge the system right after I acquired it (EBAY purchase). From what I can tell, the system is working just as good as the day the mechanic serviced the system 4 years ago. But I have to agree with my wife that it could be better. I have guages, and have measured the high and low sides (while the AC was running on high/max) as follows: High Side: About 135 PSI (might be flucuating slightly, but not sure). Low Side: Flucuating between 52 and 54 PSI; mostly stays at 54 PSI. Outside Temperature at time of measurements was 100 degrees F. Air was blowing cool/cold, but not freezing cold. I don't know what the pressures should be for this system; I'm hoping somebody could help me evaluate the system before I take it to somebody for servicing/repair; that way I might be able to tell if they know what they are doing, or if they are tyring to rip me off. Thanks for any help, and Best Regards, John Hermann |
Ads |
#2
|
|||
|
|||
R134A help needed; 1998 Suburban.
John Hermann wrote:
> ... > High Side: About 135 PSI (might be flucuating slightly, but not sure). > Low Side: Flucuating between 52 and 54 PSI; mostly stays at 54 PSI. > ... I'm not an A/C expert but the high side seems a bit low. Go to http://acsource.net/acforum/ and ask. The guys there are very knowledgable & helpful. |
#3
|
|||
|
|||
R134A help needed; 1998 Suburban.
"John Hermann" > wrote in message ... >I have a 1998 Suburban with the 5.7L V8 engine. My wife > has observed that the AC in this SUV is not quite as good > as my 1995 Blazer AC with a 4.3L V6 engine (it does very > well). I bought the Suburban used, and had a mechanic > check/charge the system right after I acquired it (EBAY > purchase). From what I can tell, the system is working > just as good as the day the mechanic serviced the system > 4 years ago. But I have to agree with my wife that it > could be better. I have guages, and have measured the > high and low sides (while the AC was running on high/max) > as follows: > > High Side: About 135 PSI (might be flucuating slightly, but not sure). > Low Side: Flucuating between 52 and 54 PSI; mostly stays at 54 PSI. > Outside Temperature at time of measurements was 100 degrees F. > Air was blowing cool/cold, but not freezing cold. > > I don't know what the pressures should be for this system; > I'm hoping somebody could help me evaluate the system before > I take it to somebody for servicing/repair; that way I might > be able to tell if they know what they are doing, or if they > are tyring to rip me off. > > Thanks for any help, and Best Regards, > > John Hermann To start off with, the pressures will vary considerably depending on a number of conditions. For instance: High side pressure varies with ambient temperature, humidity, air flow through the condenser, compressor speed, and restrictions in the system. Low side pressure varies with in cab temperature, air flow across the evaporator, humidity, heat load on the vehicle, compressor speed, restrictions in the system, Here is one scenario that you might use as a guide: Start the engine and turn on the A/C system. Place the controls on Max A/C and high fan. Run the engine at 1500 rpms for about 20 minutes with the vehicle out of direct sunlight and all the windows closed. Lets assume the ambient temperature is at 95F and the humidity is between 60% and 80%. Lets also assume the radiator cooling fan is functioning properly and the fan clutch is not slipping. The condenser and radiator fins are clean. No air dams or fan shrouds are missing. The engine is not overheating. We will also assume the A/C blower motor is functioning properly and none of the plenum blend doors are leaking or stuck. At this point the temperature inside the cab should have stabilized and the air temperature at the vents is as cold as it will get during the performance test. That should be somewhere in the neighbor hood of 45F with the fan on high and checking the temperature at the vent closest to the evaporator core. Even slight variations in ambient temperature humidity or air flow could affect the air temp as much as 10 degrees either way. While the engine is still running at 1500 rpms and the compressor clutch is engaged. The low side gage should read between 26 and 42 psi. and may cycle the compressor off occasionally. The high side should be between 225 and 275 psi. There again slight variations in conditions can affect the pressures quite a bit. If all these conditions are met then the system is probably performing up to specs. Keep in mind that any variation in the conditions will affect the pressure readings. Also consider that the Suburban has a much larger area to cool than the Blazer, and they both have basically the same capacity refrigeration system. Hope this helps. -- Kevin Mouton Automotive Technology Instructor "If women don't find you handsome, they should at least find you handy" Red Green |
#4
|
|||
|
|||
R134A help needed; 1998 Suburban.
Thanks for the responses. I too was thinking that the high side
pressure was kind of low. A couple of more things to note... 1) The gauges I'm using are a cheapo Harbor Freight set; just picked up a set for taking these measurements; so either value could be off if these gauges are known to be problematic. 2) The pressures were measured at idle (I assume around 800 RPM). 3) If the pressures are valid, then from what I read, the low side may be too high; too much charge? I was not able to measure the temp coming out of the vents; but if I were to guess, I'd say around 50 degrees. Best Regards, John Hermann ZZ > wrote: John Hermann wrote: > ... > High Side: About 135 PSI (might be flucuating slightly, but not sure). > Low Side: Flucuating between 52 and 54 PSI; mostly stays at 54 PSI. > ... I'm not an A/C expert but the high side seems a bit low. Go to http://acsource.net/acforum/ and ask. The guys there are very knowledgable & helpful. |
#5
|
|||
|
|||
R134A help needed; 1998 Suburban.
John Hermann Wrote: > Thanks for the responses. I too was thinking that the high side > pressure was kind of low. A couple of more things to note... > > 1) The gauges I'm using are a cheapo Harbor Freight set; just picked > up a set for taking these measurements; so either value could > be off if these gauges are known to be problematic. > > 2) The pressures were measured at idle (I assume around 800 RPM). > > 3) If the pressures are valid, then from what I read, the low > side may be too high; too much charge? > > I was not able to measure the temp coming out of the vents; but > if I were to guess, I'd say around 50 degrees. > > Best Regards, > > John Hermann > > > > ZZ > wrote: > John Hermann wrote: > > ... > > High Side: About 135 PSI (might be flucuating slightly, but not > sure). > > Low Side: Flucuating between 52 and 54 PSI; mostly stays at 54 > PSI. > > ... > > I'm not an A/C expert but the high side seems a bit low. > > Go to http://acsource.net/acforum/ and ask. The guys there are very > knowledgable & helpful. Your pressure reading shows a weak compressor or open expansion valve/orfice tube. If to much freon the high side would go high very quick. Does it have rear air? If just front air check or replace your orfice tube. If rear air it could be rear expansion valve or front orfice tube. If rubber hose to rear pinch it off and see if pressure starts working better. Low side should be around 30lbs and high will range around 150-250 lbs. MT -- MT-2500 ------------------------------------------------------------------------ MT-2500's Profile: http://www.automotiveforums.com/vbul...?userid=382930 View this thread: http://www.automotiveforums.com/vbul...d.php?t=593497 http://www.automotiveforums.com |
#6
|
|||
|
|||
R134A help needed; 1998 Suburban.
Yes, the Suburban does have rear air. Another thing I forgot to mention is the AC compressor was engaged the entire time I was testing; it never cycled off. Best Regards, John Hermann MT-2500 > wrote: John Hermann Wrote: > Thanks for the responses. I too was thinking that the high side > pressure was kind of low. A couple of more things to note... > > 1) The gauges I'm using are a cheapo Harbor Freight set; just picked > up a set for taking these measurements; so either value could > be off if these gauges are known to be problematic. > > 2) The pressures were measured at idle (I assume around 800 RPM). > > 3) If the pressures are valid, then from what I read, the low > side may be too high; too much charge? > > I was not able to measure the temp coming out of the vents; but > if I were to guess, I'd say around 50 degrees. > > Best Regards, > > John Hermann > > > > ZZ > wrote: > John Hermann wrote: > > ... > > High Side: About 135 PSI (might be flucuating slightly, but not > sure). > > Low Side: Flucuating between 52 and 54 PSI; mostly stays at 54 > PSI. > > ... > > I'm not an A/C expert but the high side seems a bit low. > > Go to http://acsource.net/acforum/ and ask. The guys there are very > knowledgable & helpful. Your pressure reading shows a weak compressor or open expansion valve/orfice tube. If to much freon the high side would go high very quick. Does it have rear air? If just front air check or replace your orfice tube. If rear air it could be rear expansion valve or front orfice tube. If rubber hose to rear pinch it off and see if pressure starts working better. Low side should be around 30lbs and high will range around 150-250 lbs. MT -- MT-2500 ------------------------------------------------------------------------ MT-2500's Profile: http://www.automotiveforums.com/vbul...?userid=382930 View this thread: http://www.automotiveforums.com/vbul...d.php?t=593497 http://www.automotiveforums.com -- John Hermann Buy, Sell, Trade, and Repair Video and Pinball Machines. Located near Dallas, TX. http://www.geocities.com/SiliconValley/Circuit/8393 |
#7
|
|||
|
|||
R134A help needed; 1998 Suburban.
I agree that it sounds like the compressor is weak. Is it making any
noise which could indicate a failed TXV for the rear A/C and liquid slugging? Also check to make sure the A/C belt is not slipping or loose. Head pressure should be at least 50-60PSI higher. Most likely you need a new compressor. Replace the drier and/or accumulator as well and observe the pressures as you charge (after evac of course) with both the front and rear A/C on. If the rear TXV is gone and flooding the rear evap, your suction pressure won't come down properly and you may start hearing the compressor chugging liquid. If you do, stop and turn it off before damaging the new compressor and replace the rear TXV. These are known to be bad on Suburbans. The sensing bulb clip that attaches it to the evap return line does not work great and causes the TXV to open fully. dave mc |
#8
|
|||
|
|||
R134A help needed; 1998 Suburban.
With the engine running at 600-700 rpm the compressor is going to be
weak.Take the readings with the engine running at 1500-2000 rpm. Air should be on recycle. Pumping 100 degree outside air at idle won't get you much temperature drop. "davemac" > wrote in message ups.com... >I agree that it sounds like the compressor is weak. Is it making any > noise which could indicate a failed TXV for the rear A/C and liquid > slugging? Also check to make sure the A/C belt is not slipping or > loose. Head pressure should be at least 50-60PSI higher. > > Most likely you need a new compressor. Replace the drier and/or > accumulator as well and observe the pressures as you charge (after evac > of course) with both the front and rear A/C on. If the rear TXV is > gone and flooding the rear evap, your suction pressure won't come down > properly and you may start hearing the compressor chugging liquid. If > you do, stop and turn it off before damaging the new compressor and > replace the rear TXV. These are known to be bad on Suburbans. The > sensing bulb clip that attaches it to the evap return line does not > work great and causes the TXV to open fully. > > dave mc > |
#9
|
|||
|
|||
R134A help needed; 1998 Suburban.
Woody wrote: > With the engine running at 600-700 rpm the compressor is going to be > weak.Take the readings with the engine running at 1500-2000 rpm. Air should > be on recycle. Pumping 100 degree outside air at idle won't get you much > temperature drop. > The readings should ideally be at 1500 RPM, so yes I agree that they should be re-taken. but sorry, even at 800 RPM they should be better than this. You will wait a long time to cool a Suburban at 100 deg F ambient with these pressures. Head pressure at 100 F ambient should be on the order of 220-250 PSI. davemc |
#10
|
|||
|
|||
R134A help needed; 1998 Suburban.
Kevin, with a head pressure of 135PSI, he definitely does not have a
condensor or fan clutch issue, at least not as a primary problem. Condensor issues will show with too high a head pressure normally. dave mc |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Equipment needed to self-service R134a air conditioner | Masospaghetti | Technology | 17 | July 14th 06 10:41 PM |
AWA [OFFER] Refrigerants: R134a Blend, R12 Blend, R22, Purity 99.98% R134a, R600a | [email protected] | General | 0 | March 30th 06 11:52 AM |
1998 doge daytona help needed | DAVID FRITH | Dodge | 1 | June 22nd 05 12:35 PM |
Newbie here...Honda civic 1998..help needed | [email protected] | Honda | 9 | May 13th 05 02:35 PM |
Forza Car List | Rob Berryhill | Simulators | 19 | May 7th 05 11:37 PM |