Mr. Dude with a face

Hi everyone! As summer time is coming around, I like others, am using my A/C more often, and I have noticed that it is just not blowing as cool as I think it should. I am in Utah, so we experience some high summer temperatures, up past 100. Lately it has been around 80, but we have had some 90 degree days recently too. I have noticed that even on a cooler day the A/C cant manage to keep that cab cool. I have had a thermometer in the vent for a few weeks watching the temp, and with the A/C on, recirculate or fresh air, low fan or high fan, I have yet to see it get cooler than 60. From my understanding it should be more like 40, correct? I also have noticed that when the A/C is on, that the compressor clutch never disengages. From my understanding it is supposed to come on and off. I don't know much about A/C so I figured I would ask for some opinions before I put my tail between my legs and take it to a shop. If is applicable the vehicle in question is a 1998 GMC sierra/K1500, the fan is driven by the engine (clutch fan?). I have already checked the freon level with a simple pressure gauge for home use, and it seems to be perfectly within where it should be. Note, it was not a full on manifold gauge like professionals use, so that is open to interpretation. I have been advised to check and see if the condenser is plugged up with bugs or other miscellaneous road goobers. I am currently waiting for it to get dark out side so I can look with a flash light, which is customary, I will post the verdict latter. Thanks for any tips, and hopefully save me some change!

Mr. Dude with a face

Okay, just went out and I can shine a light through the radiator and condenser just fine and see light through, to me it does not look that dirty.

tech2

some ac systems don't cycle on and off...they use variable displacement compressors so this is most likely normal operation.

refrigerant level checks by pressure aren't accurate. recovering the system by weight with an ac machine is the accurate method.

a quick method is to feel the temp of the accumulator and evaporate inlet tube. if the inlet is colder...you are probably low on refrigerant.

performance wise a new vehicle at 80*F should put out 45*F at the center vent at 1000rpm

if the system works better driving down the road...it may be a fan issue
if the system works better when the engine is held at high rpm 2500....the compressor may be worn.

however first step to any ac diagnosis is to: verify system performance. if poor, use an accurate method to verify charge level.

Mr. Dude with a face

@tech2 Thanks for the tip. Thankfully I have another truck to compare to, and I believe that the compressor on that one clicks on and off. If you could, could you explain your method for checking the level of refrigerant in more detail, I don't know much about A/C, and am unfamiliar with anything other than the major components. Thanks for the reply!

Mr. Dude with a face

I have noticed and forgot to include that the function of the A/C does not seem to change for better or worse regardless of speed, or engine RPM. Also, if my compressor never seems to click off, when it in fact should, what does that mean? Could it mean a bad compressor, or something else?

tech2

there are different builds for your truck..some came with a variable compressor some were a cycling clutch system. you would have to check you compressor to see which you have. if a cycling clutch system doesn't shut off...it would freeze the evaporator

Mr. Dude with a face

@tech2 Do you know how I would check to see if i have one that is supposed to come on and off, or one of those variable ones? Also, if i have one that is supposed to come on and off, what could it mean for me since mine is on all of the time? Thanks for the help!

Mr. Dude with a face

@tech2 Okay, I don't know if I mentioned this before, but my father owns that exact year make model and trim truck that I have. I just asked him, and his truck, which has A/C that functions as normal, the compressor does click on and off. So does that mean that mine would too? The trucks were only built a few months apart from one another. I also don't think they would have changed the system, since 98 is the last model year or our trucks.

oilcanhenry

I own a 1998 Chevy K-1500 4x4 pickup. I WAS going to become a tech, or mechanic, but ended up as a professional driver. That said, I specialized in automotive air-conditioning in HS & Junior College. What Tech2 said was spot on good advice, but he is a professional tech. You ought to show 30-35 PSI on the Low-side with those cheap A/C can gauges. They are not all that accurate, but if you have pressure, which I'll assume you do, you have a 22-year-old Chevy. Might be your compressor going bad, which can plug up your orifice-tube as it deteriorates. You didn't mention the mileage on your Chevrolet, but if it's very high then it's very possible that its a leak, or the compressor going south and/or a partially plugged up orifice-tube, which can collect particles of matter.

You may still be low on R-134A refrigerant, kinda hard to tell without a high and low side reading with a good A/C gauge set. 60 F is much too hot. As tech2 said, it should be 45 F or lower at the center vent, even at 100 F outside temps. You can try adding one more can of R-134A, but ALWAYS wear gloves and face protection when working on an A/C system. I think that you may well have a leak somewhere in your system and its usually in the engine compartment or condenser and not the evaporator in the cab.

Legally, to allow R-134A to be extracted for repairs, it needs to be recycled at a shop, which isn't cheap, but A/C is always expensive. If you find that your compressor is going south, and if so the system will need to be flushed out before you can start adding parts and R-134A refrigerant, and the air purged from the system for at least half an hour to an hour. You'll also need to change the receiver/drier on the fender-well, the big aluminum can mounted there, as well as the orifice-tube in the condenser unit upfront of the radiator.

Mr. Dude with a face

@oilcanhenry Wow, thank you for the advice! So how would you recomend going from here? Do you think I should rent one of the maniflold gauges to really see if my pressures are acurate? And to your point of milage, we have got a few, about 184K.