jcwren
New member
I have a T574HST I bought in late 2024. The air conditioning was intermittent last year, and has finally gone out on it.
I first suspected a leak, so I put a set of gauges on it, it's got about 100PSI static pressure on a 90F day, so I shouldn't need any R134a. Checked what I think should be the low pressure cut-off switch, it's closed (0 ohms) when the engine not running. However, the compressor clutch isn't pulling in when the blower is on and the AC switch on. Measured the resistance across the clutch coil, it's 3.6 ohms, so the coil should be good. I can't find any signs of rodent damage anywhere.
I haven't found an actual schematic for it yet. I can't find ANY indication that there's a fuse or separate relay for the clutch. It's possible the AC on/off switch is bad, but I wasn't yet ready to drop the headliner shell to pull it out for testing.
Has anyone run into AC issues, and if so, what went bad? I'm pretty confident it's an electrical issue, but I don't want to go too far and void the warranty. I would take it to the dealer I bought it from, but they closed and the nearest one is 92 miles away, and I don't have a truck/trailer combination that can move a T574 with tire ballast.
The TYM documentation is really bad. Half the AC documentation in the workshop manual is about how to read the sight glass on the drier. But there is no drier, not on the hose routing diagram, nor in real life. Detailed electrical details are non-existent.
I first suspected a leak, so I put a set of gauges on it, it's got about 100PSI static pressure on a 90F day, so I shouldn't need any R134a. Checked what I think should be the low pressure cut-off switch, it's closed (0 ohms) when the engine not running. However, the compressor clutch isn't pulling in when the blower is on and the AC switch on. Measured the resistance across the clutch coil, it's 3.6 ohms, so the coil should be good. I can't find any signs of rodent damage anywhere.
I haven't found an actual schematic for it yet. I can't find ANY indication that there's a fuse or separate relay for the clutch. It's possible the AC on/off switch is bad, but I wasn't yet ready to drop the headliner shell to pull it out for testing.
Has anyone run into AC issues, and if so, what went bad? I'm pretty confident it's an electrical issue, but I don't want to go too far and void the warranty. I would take it to the dealer I bought it from, but they closed and the nearest one is 92 miles away, and I don't have a truck/trailer combination that can move a T574 with tire ballast.
The TYM documentation is really bad. Half the AC documentation in the workshop manual is about how to read the sight glass on the drier. But there is no drier, not on the hose routing diagram, nor in real life. Detailed electrical details are non-existent.
