AC Cycling Help Please
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Junior User
Joined: Mar 2011
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AC Cycling Help Please
Have a 2018 F350 with the 6.2, my dealer cant get me in for a couple weeks and my ac is hardly working. Bought the truck over winter so never noticed till it warmed up but the ac is short cycling. The compressor engages for about 5-8 seconds and during that time ice cold air. Then is disengages for 3-5 seconds and repeats. Only once I turned on max ac and it seemed to stay on till I turned off that setting and hasnt done it again. Just to humor myself I bought two cans of r134a since I already had one of the single gauges. When the compressor is on I get 28-30 psi when its 75 degrees out. Added both cans and nothing changed, same psi, same short cycling. Any suggestions from here to check? Thanks
Fleet Owner
Joined: Apr 2008
Posts: 24,324
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From: 0,0,1
We would also need to know what the high side is reading.
FTE Legend
Joined: Nov 2015
Posts: 30,981
Likes: 4,134
From: Angier, NC
Yes that would be nice but in my case, 134a change over on my 81 F100, I dont have the right fitting for the gauge hook up.
I used the low side gauge for PSI to temp and the tempature of the cold line going into the evap and used supper cooling to supper heat split.
My son who was doing the work this time said we have a 3*f split and he would like to see a 5*f split.
Again with out the high side reading he could not see 100% what was going on but he thinks there is to much oil in the system from when I put it together late last summer.
I know what I first got the system working I had to get the low side up to 50 - 55 psi to get the vents to blow cold.
Yesterday he stopped at high 40's psi when we took it for a test drive we got 38*f out the vent with 80*f OAT I am happy with that.
BTW mine was doing the same before this fix & recharge. I hope the O-ring where all the oil was was bad.
Dave ----
I used the low side gauge for PSI to temp and the tempature of the cold line going into the evap and used supper cooling to supper heat split.
My son who was doing the work this time said we have a 3*f split and he would like to see a 5*f split.
Again with out the high side reading he could not see 100% what was going on but he thinks there is to much oil in the system from when I put it together late last summer.
I know what I first got the system working I had to get the low side up to 50 - 55 psi to get the vents to blow cold.
Yesterday he stopped at high 40's psi when we took it for a test drive we got 38*f out the vent with 80*f OAT I am happy with that.
BTW mine was doing the same before this fix & recharge. I hope the O-ring where all the oil was was bad.
Dave ----
Cross-Country
Joined: Feb 2017
Posts: 76
Likes: 25
From: GA
Have a 2018 F350 with the 6.2, my dealer cant get me in for a couple weeks and my ac is hardly working. Bought the truck over winter so never noticed till it warmed up but the ac is short cycling. The compressor engages for about 5-8 seconds and during that time ice cold air. Then is disengages for 3-5 seconds and repeats. Only once I turned on max ac and it seemed to stay on till I turned off that setting and hasnt done it again. Just to humor myself I bought two cans of r134a since I already had one of the single gauges. When the compressor is on I get 28-30 psi when its 75 degrees out. Added both cans and nothing changed, same psi, same short cycling. Any suggestions from here to check? Thanks
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
Likes: 79
From: Mooresville, NC
Normal suction (low side) pressures should be:
26-45 (70 degree ambient) to
50-75 (100 degree ambient)
Normal discharge (high side) pressures should be:
150-225 (70 degree ambient) to
220-340 (100 degree ambient)
There will be variations in the numbers above given differences in type of system. Hard to diagnose in the absence of data/information, but you're probably looking at:
Low refrigerant (please don't (like many knuckleheads out there) use the single gauge "refills" sold by AutoMoan, O O What a Joke, etc ---more often than not these knuckleheads are dumping CHIT in the atmosphere because they don't know what they're doing --- take to an EPA 609 Certified Tech)
Restricted AC suction line
Faulty AC cycling switch --located at at accum, rcvr/drier normally
Faulty AC high pressure switch (normally clips off excess pressures, but can affect the AC cycling switch since they're connected) -- found near compressor normally
Faults in electronics, wiring, etc (if electronically controlled)
26-45 (70 degree ambient) to
50-75 (100 degree ambient)
Normal discharge (high side) pressures should be:
150-225 (70 degree ambient) to
220-340 (100 degree ambient)
There will be variations in the numbers above given differences in type of system. Hard to diagnose in the absence of data/information, but you're probably looking at:
Low refrigerant (please don't (like many knuckleheads out there) use the single gauge "refills" sold by AutoMoan, O O What a Joke, etc ---more often than not these knuckleheads are dumping CHIT in the atmosphere because they don't know what they're doing --- take to an EPA 609 Certified Tech)
Restricted AC suction line
Faulty AC cycling switch --located at at accum, rcvr/drier normally
Faulty AC high pressure switch (normally clips off excess pressures, but can affect the AC cycling switch since they're connected) -- found near compressor normally
Faults in electronics, wiring, etc (if electronically controlled)
Last edited by F350 1990; Apr 22, 2021 at 09:57 AM.
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