AC not staying cold
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Trailering
Joined: Aug 2017
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AC not staying cold
I have a 1999 f250 super duty. I had my AC purged, leak checked and replenished. They said not leaks. Worked great for 1 season and not it's blowing warm air again. What would cause this to happen if there are no leaks in the system?
Thanks
Dean
Thanks
Dean
Fleet Mechanic
Joined: Aug 2011
Posts: 1,576
Likes: 262
98% chance there is a leak in the system
1% chance there is an electrical issue (low pressure switch, high pressure switch, AC clutch relay, AC clutch coil or hvac controls.
1% chance the clutch air gap is too large and the coil can’t pull the clutch in or the bolt may have backed out and fallen off possibly also half the clutch fell off also.
Most shops vacuum down the system for a few minutes, let it sit for 10-30 minutes and see if the pressure changes in the system, if it stays then they say it’s leak free and charge it but in reality that will only show a gross leak and not a small leak. Small leak could take months or more to leak enough refrigerant out for the system not to work, hence the 98% possibility there’s a leak.
1% chance there is an electrical issue (low pressure switch, high pressure switch, AC clutch relay, AC clutch coil or hvac controls.
1% chance the clutch air gap is too large and the coil can’t pull the clutch in or the bolt may have backed out and fallen off possibly also half the clutch fell off also.
Most shops vacuum down the system for a few minutes, let it sit for 10-30 minutes and see if the pressure changes in the system, if it stays then they say it’s leak free and charge it but in reality that will only show a gross leak and not a small leak. Small leak could take months or more to leak enough refrigerant out for the system not to work, hence the 98% possibility there’s a leak.
Fleet Mechanic
Joined: Aug 2011
Posts: 1,576
Likes: 262
Generally areas that leak will also leak out oil from the AC system and that area will be oily and dirty. Most leaks are from hose crimped ends and piping connection o-rings going bad, the condenser generally doesn’t leak by itself but road debris can beat it up and cause leaks, compressor seals can go bad, evaporator cores are usually pretty good, the test ports shrader valves can leak and if the caps are missing they tend to go bad also.
Any hose or pipes can rub on something and get holes in them also. I would start by just doing a visual on any of the AC system components and look for wet/oily/dirty spots to check for leaks, after that your going to need a gauge set to check pressures and see if your low on charge or you have another issue (electrical/mechanical).
Whatever you do NEVER put stop leak in an AC system, you will clog up the orifice tube/expansion valve and that will require a complete flush and multiple part replacement depending what gets clogged up.
Any hose or pipes can rub on something and get holes in them also. I would start by just doing a visual on any of the AC system components and look for wet/oily/dirty spots to check for leaks, after that your going to need a gauge set to check pressures and see if your low on charge or you have another issue (electrical/mechanical).
Whatever you do NEVER put stop leak in an AC system, you will clog up the orifice tube/expansion valve and that will require a complete flush and multiple part replacement depending what gets clogged up.
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