AC stopped - high pressure cutoff?

[JHZR2]

Today I was driving my 96 Ram Cummins in some pretty severe traffic. AC is working well, though it has a very small leak in chasing (slow enough to take a calendar year to short cycle the compressor and have reduced cooling). The charge in there is appropriate per the operational pressures in the fsm, for the ambient conditions.

All of a sudden, the air got warm, and the airflow dropped significantly. I turned it off and got to my destination just a minute or two later. Shut the vehicle off, and upon restart, no issues at all. Worked great for the rest of the evening.

Any thoughts on what could cause this?

Belt is great, compressor works well. I had added a bit of 134a, but tracked the pressure per the FSM. Could it be that the heat and traffic could have caused it to cutoff on high pressure?

I don’t think the evaporator is frozen, it is definitely condensing water.
Any ideas/suggestion?

 

[clinebarger]

Pretty common issue with Viscous Fan Clutches on air to air Intercooled Diesels. My '97 Ram CTD would do it more often than my '06 Chevy LBZ.

The Fan Clutch isn't getting a "HOT Air" signal from the A/C Condenser trough the cooling stack, As the ECM doesn't control the cooling fan....It's only defense is to turn the compressor clutch off.

 

[SHOZ]

My bet is the evaporator is freezing up. Hyundai has a problem with this and it's usually the evap temp sensor that is bad. Or maybe it just needs reseated. Should be kicking the AC compressor off at around 35F or so.

 

[mk378]

If it happens again pull over and check under the hood. See if the compressor is turning and if there is ice on the line leaving the evaporator, which would mean the whole evaporator is frozen.

 

[JHZR2]

My bet is the evaporator is freezing up. Hyundai has a problem with this and it's usually the evap temp sensor that is bad. Or maybe it just needs reseated. Should be kicking the AC compressor off at around 35F or so.

If it happens again pull over and check under the hood. See if the compressor is turning and if there is ice on the line leaving the evaporator, which would mean the whole evaporator is frozen.

Turning the vehicle off for a minute, then back on solved it completely. It hasn’t happened since. So I don’t think it’s frozen. No other signs of that being the case.

Pretty common issue with Viscous Fan Clutches on air to air Intercooled Diesels. My '97 Ram CTD would do it more often than my '06 Chevy LBZ.

The Fan Clutch isn't getting a "HOT Air" signal from the A/C Condenser trough the cooling stack, As the ECM doesn't control the cooling fan....It's only defense is to turn the compressor clutch off.

Thanks. I guess this is it, just too hot and it happened.

What parameter is commanding the compressor clutch off? Air temperature, refrigerant pressure, or something else?

 

[wag123]

My bet is the evaporator is freezing up. Hyundai has a problem with this and it's usually the evap temp sensor that is bad. Or maybe it just needs reseated. Should be kicking the AC compressor off at around 35F or so.

+1
"All of a sudden, the air got warm, and the airflow dropped significantly." This is the tip off. If the system is slightly low on freon it will do this. Put the gauges on it and have a look.

 

[clinebarger]

Turning the vehicle off for a minute, then back on solved it completely. It hasn’t happened since. So I don’t think it’s frozen. No other signs of that being the case.



Thanks. I guess this is it, just too hot and it happened.

What parameter is commanding the compressor clutch off? Air temperature, refrigerant pressure, or something else?

Guess I missed the drop in air volume, Though I've never seen a iced over evaporator thaw in a minute.

The ECM controls the Compressor Clutch Relay, High & Low side pressure switches are wired in series between the A/C Control head & ECM on the A/C Request Circuit

 

[JHZR2]

Guess I missed the drop in air volume, Though I've never seen a iced over evaporator thaw in a minute.

The ECM controls the Compressor Clutch Relay, High & Low side pressure switches are wired in series between the A/C Control head & ECM on the A/C Request Circuit

Yeah it felt like the air slowed down a lot, and got really humid, fast. I have. Y double thst it was frozen at all. Performance otherwise was great, cold air, good pressures, draining evaporator, etc. It’s more plausible to me that something cut out for whatever reason, and/or while the drain is flowing, the evaporator got overwhelmed with water.

 

[Chris142]

Check the clutch gap