Air conditioner acting up “fixed”

[crazykid1994]

Ok. It’s been pretty hot and humid here in south Florida. My ac has cut off sporadically a few times during this heat. It’s usually only for a few seconds as I’m the only one that notices. I can smell a humid smell through the ac vents when it happens so I know the ac shut off. I’ve done some fiddling with the truck to try and deduce why it’s shut off. I’m pretty sure it’s from heat soak causing high pressure in the lines. I can touch the vacuum line from the firewall to the compressor and with the ac on it’s warm to the touch. The high pressure line is extremely hot and will burn you. Under hood temps are high currently with these high temps. I installed some insulation on the vacuum line from the firewall all the way to the compressor to see if it would help. Well now my vacuum line is cool all the way to the compressor. I’m pretty sure my ac feels about 3-4° colder at the vents even with temps into the mid 90s here. Also my ac has not cut off on me since installing the insulation. It is closed cell fire retardant insulation bought at home depot in the hvac department. It is for ac vacuum lines and water heater hot side lines. It is good for heat and cold and being closed cell will not absorb moisture. In theory the compressor should now run cooler which should increase the compressor efficiency and prolong the life of the compressor as well.

 

[cityredneck]

interesting, last week or the week before i noticed that my ac was on but it seemed like it was warming up a little bit and then would start cooling again. i wonder if mine was doing the same thing.

last weeks temps in arlington, tx area was baking pretty good 100+ degrees.

i might try this but then again we are getting a bunch of rain and the temps dropped to the 80s.

 

[MRFREEZE57]

the only way to really know what is going on is to put a set of gauges on it and see what is going on. sounds like it could be cycling off on high pressure, have you checked the condenser to see if is clean?
insulating the suction line can help get some cooling vapor back to the compressor. when you say the high pressure line is very hot are you checking the discharge line ( the smaller one from the compressor to the condenser ) or the liquid line going from the condenser to the evaporator? in your climate the discharge will be quite hot, the liquid line will likely be very warm but touchable. one other question, have you tapped into the system before, and possible got air and non condensables in the system? just armchair diagnostics but still a set of gauges is your best friend for troubleshooting this issue.
here where I live we rarely get the temps and humidity you have and the truth is about the only time my AC is used is in the winter when it cycles on with the defroster.

 

[crazykid1994]

the only way to really know what is going on is to put a set of gauges on it and see what is going on. sounds like it could be cycling off on high pressure, have you checked the condenser to see if is clean?
insulating the suction line can help get some cooling vapor back to the compressor. when you say the high pressure line is very hot are you checking the discharge line ( the smaller one from the compressor to the condenser ) or the liquid line going from the condenser to the evaporator? in your climate the discharge will be quite hot, the liquid line will likely be very warm but touchable. one other question, have you tapped into the system before, and possible got air and non condensables in the system? just armchair diagnostics but still a set of gauges is your best friend for troubleshooting this issue.
here where I live we rarely get the temps and humidity you have and the truth is about the only time my AC is used is in the winter when it cycles on with the defroster.

All factory still. It has never been touched. Condenser is clean. I rinse it out every time I wash the truck. I do not have gauges to check with either. The line from the condenser to the evap was burning hot. It’s definitely not burning hot anymore since insulating the vacuum line. My ac runs all year. Coolest weather we generally get is in the 50s during winter if we are lucky and that’s only for a few days.

 

[MRFREEZE57]

All factory still. It has never been touched. Condenser is clean. I rinse it out every time I wash the truck. I do not have gauges to check with either. The line from the condenser to the evap was burning hot. It’s definitely not burning hot anymore since insulating the vacuum line. My ac runs all year. Coolest weather we generally get is in the 50s during winter if we are lucky and that’s only for a few days.

the liquid line ( the one between condenser and evap) should not be burning hot. sounds like you need to get a tech to check it out.

 

[crazykid1994]

the liquid line ( the one between condenser and evap) should not be burning hot. sounds like you need to get a tech to check it out.

Since insulating the line it is no longer burning hot. I think the Ambient heat was causing exaggerated pressure in the line as well as high engine bay temps. Heat soaking the vacuum line was drawing excessive heat into the compressor more so than the condenser could remove. Theoretically all that heat into the compressor was making it work harder which would increase heat and reduce efficiency. Like stated since I’ve added the insulation to the vacuum line everything has been fully operational and no more issues and the liquid line is no longer burning hot.

 

[Gus0316]

Good morning from Ohio,
New member here and an HVAC/Power Generation/Robotics and Controls Technician by trade. Mostly work in industrial Automotive Factory/Warehouse and Refrigeration units but also 609 certified. I agree with MRFREEZE57. I would also add that you can use temperature readings and then a pressure temperature conversion chart to give us more details. Specifically I would like to know what Refrigerant is in the system R134A or R1234YF? (I have not looked at your year model) Short Cycling (as you described) could be caused by high head pressure. Which is exactly what MRFREEZE57 was going after and rightfully so.
I have also seen evaporator overloading cause high head pressure on undersized units (although not in a vehicle).
There are several factors at play.
Most A/C Systems are designed to operate at 95 Ambient. (Geottl is only one I know of designed at 110)
I would like to help but need more info.
Please take loaded (system under full load, windows open Max Cool etc). temp readings at Condenser inlet (discharge line, will be hot so be careful, also careful of any moving parts)/outlet (Liquid Line just before the Expansion Valve) and Evaporator outlet and about 4-6 inches from Compressor inlet (Suction Line)
Please leave your insulation in place and take the readings under it if possible.
Once I see those numbers I will have a better idea.
I work second shift so probably will be some lag in my response. Just so you are aware

 

[Gus0316]

Another bit of information.
Automotive systems use rubber hoses for vibration isolation. If you look closely at the hoses you will see pin holes every so many inches on every make and model. These are to prevent bulges from outgassing. So when you hear "probably needs a charge" that's why and can be true in vehicles. In a residential home or industrial application an A/C that needs a "Charge" means it's leaking someplace and needs repair as the lines are Copper/Aluminum and shouldn't be leaking.

 

[fijicorey]

A/C is a must here in Florida during the summer! I also run mine pretty much all year. I had some issues with my A/C earlier this summer and it turned out to be the wiring going to the compressor. Apparently the connector had just completely fallen apart. My symptoms was that the A/C would blow warm intermittently with no real pattern. I had that fixed and have had no issues since.

 

[Gus0316]

Sounds like maybe the connection wasn't solid and it over heated due to amp draw? Was it melted?
My question would be did the wiring suffer annealing? If so you may have further issues down the road. Make a check with engine off to see if the wire insulation is damaged. (Crisp or hard and not flexible). If you can see actual wire look for discoloration in the strands. The reason this is important is conductivity. Annealing reduces the ability of electron flow (causes higher resistance) which causes higher amp draw and heat in the conductor. This eventually leads to a burnt wire. Good info to keep an eye on for all of us for sure. Thank you for posting your experience.