Questionwhat are the correct A/C low and high pressure readings on a 1999 Chevy Tahoe V8?
Is there a sight glass on this model?
AnswerPaul,
Pressure and temperature are relative. If one goes up so will the other. So it is impossible for me to tell you what your pressure readings should be without knowing the temperature of the ambient air outside. It will be different today from what it will be tomorrow.
Here is how to figure it out though.
Take the ambient air temp and subtract 35 from it. Then cross reference this number to a pressure/temperature chart for the refrigerant you are using and that number you find is what you should read on your low side at idle.
example: if it is 90 degrees outside, subtract 35 (because you are using a forced convection evaporator) that leaves 55. At 55 degrees the pressure for R134a will be roughly 51 psig. This is your low side reading.
For your high side you will take the ambient temperature and add 30 to it (froced convection condensor) then cross reference the number.
example: 90 degree day add 30 degrees = 120 degrees. At 120 degrees the pressure for R134a is roughly 170psig. This is yor high side reading.
So on a 90 degree day your gauges will read low 51 high 170.
On an 80 degree day they will read low 39 high 145.
Here is a good site to convert if you want it.
http://www.csgnetwork.com/r134apresstempconv.html
As for a sight glass, no, I do not believe that they put one in the 99 tahoe. But if they did... it will be located on the top of your receiver.
Thank you for your question. I hope I was of some help. If so, please remember to rate this answer. If I can do anything further to assist you now or in the future, please do not hesitate to ask. Thanks again and good luck in everything.
