Screg

Tony, gave you some bad numbers on the R134a numbers should read 90 degrees outside temperature should read in range of 250-270 PSI on gage pressure. Lot's of things can come to play like clutch fan not pulling enough air over condenser to convert highpressure gas to warm liquid for orfice tube or expansion valve to feed evaporator. If you see return line to compressor (suction side of compressor) sweating (not frosting) u probably have good charge and good airflow over evaporator. Sorry about the bad info. Screg.

tonyvisone

thanks for the info screg. i did not try letting out any pressure, but i did buy a set of gauges today. mainly because i want to learn how to fix AC systems, or atleast diagnose them.

the low fluctuated between 20 and 50 PSI (-4 and 13 R134-A units.... not sure what the units are here)... see the video

the high fluctuated between 50 and 80 PSI (15 and 25 units??)
IMG_3075_zps6ef01872.mp4 Video by tonyvisone | Photobucket



not to complicate this thread, but i also tried the gauge on my families spare truck, a 98 tahoe 5.7L. it showed 0 PSI on low and high. but i noticed that the compressor wasnt engaging... i metered the plug going to the compressor and it showed about 45 mV with the ac on OR off..

tonyvisone

anybody?

edac

Tony, your still low on freon. pressures relate to temperature, Find leak, find out how much freon your vehicle takes and add freon.

Screg

Tony, watch new gauges video and see now you are low on refrigerant. As Edac stated follow the temperature/ pressure relationship on the chart he posted. Find out what outside temp(atmospheric temp) is, look at chart Edac provided find that outdoor temp and read across to right, it will give the proper PSI at this temperature. That's the PSI you should read on your new gauges, Evaporator/low pressure blue gauge, Condenser/high pressure red gauge. Your gauges are reading Centigrade, just disregard the C temps on your gauges and use the PSI reading. Then refer to the temperature/ pressure chart and let it do the work for you. It gives F temps relative to PSI pressures, these are the same pressures you're reading with your gauges just they do their temps in F. If you are loosing refrigerant then you have leak. Refrigerant gets very costly when you have to constantly add but worst than that if you do'nt keep enough refrigerant in the system you can't cool compressor properly. When charged right it should sweat a bit on suction side of compressor hose aluminum connector. You can look for leaks the old timey way with leak tech solution or make some out of dish washing solution and water. Add refrigerant so compressor runs to pressure system for a few minutes that shut motor off and system will nuetralize pressure over intire low and high side. Spray soap solution over all line connections and condenser just keep looking or have someone with refrigerant sniffer hunt that leak down. Could be something simple like o-rings at liquid line, condenser lines, or manifold o-rings at compressor. Hope this helps Screg.

tonyvisone

update

still havent fixed this, or properly diagnosed. i did a few brake projects on the truck (all pads, e brake adjust, abs sensor fix, a few brake lines, and sway bar links).

so i brought the truck down to a local guy. he has an 01 silverado (mines a 99).

his AC works good and his readings were: Low: 45 and High: 300. both were steady values...

mine on the other hand (after we added some freon) was: Low: 20-75 and High: 90-105, both fluctuating....

it seems my low is too high and my high is too low?? does that mean something specific?

tonyvisone

anybody??

tonyvisone

still looking for help on this..........

to reiterate so you dont have to read back....

99 silverado 5.3L

Low: 20-75 psi and High: 90-105 psi, both fluctuating when the compressor engages..... see video above (okay i guess you do have to go back if you want to see the video) it seems my low is too high and my high is too low?? does that mean something specific?


also, i have a 98 tahoe 5.7L and the compressor plug only gets about 50 mV whether the AC switch is on or off....

in2pro

I am having similar issues on a caravan, and its my understanding that the compressor is going out when you see those numbers... have you ever charged it with Freon? if so did you use a full gauge set of gauges or a single gauge?

Give this site a read and see if it helps.. http://www.agcoauto.com/content/news/p2_articleid/257

tonyvisone

i have put freon in, and i have used a set of dual gauges... the compressor is probably going, just looking to confirm this i guess..

as for the tahoe, im thinking to try putting wires from the battery with a toggle switch, but still looking for an answer on that as well