Thread: HyChill in 2.7 or 3.0

Originally Posted by Graeme

Is anyone using HyChill in a 2.7L or 3L D4?

I've gone the complete circle chasing why the a/c system only cools while idling, having replaced the compressor control valve (possibly because I powered it on full 12V) and replaced the ATC ecu (likely damaged trying to discover why the compressor control valve wasn't being powered). It seems that the compressor control valve is set to minimum flow once revs are increased a little and flow isn't restored by idling the engine again, but flow is restored by restarting the engine.

From the WSM...
The ATC module automatically adjusts the displacement of the A/C
compressor between the minimum and maximum values, to match the thermal load of the evaporator. By matching refrigerant flow and the thermal load of the evaporator, the ATC module maintains cabin comfort whilst also considering fuel economy.

I'm wondering if the ATC ecu detects a discrepancy in the performance of the system once engine revs exceed around 1000 rpm due to the refrigerant being HyChill rather than the specified R134A so idles the system.

Yes I have.

And the system died, but I've been blaming a partially blocked condenser.

I have also been wondering if the variable displacement compressors don't like the Hychill, but there doesn't seem to be any logical reason for this.

Anyway the compressor destroyed itself and I'm still not sure why. (Actually it might be 2).

I really hope you get to the bottom of this, it's so frustrating, and so difficult to swap parts on these systems. I know I said earlier this thread was giving me PTSD, and I wasn't joking!

Thanks for your comments. I really think that the ATC module is shutting down the system rather than a blockage because the a/c system never restarts after extended idling but starts cooling as soon as the engine is restarted.

I should add that the first HyChill fill that showed high low-side pressures and low high-side pressures that prompted the replacement of a suspected blocked dryer was done by 1 workshop. The 2nd HyChill fill was done by another workshop who only had an on/off switch for the compressor control valve fitted by me rather than a working ATC system controlling the compressor. He filled the HyChill recommended quantity but added a little more to get the system as cold as he thought it should be, noting that the compressor was running at maximim capacity. Also, this mechanic stated that he usually has to add a little more, possibly indicating that his measuring equipment might be optimistic.

I'll put the gauges on tomorrow morning. The IIDtool shows static pressure of around 100 psi and around 160-170 psi at ambient 30 deg, and the evaporator temperature around 10 deg with the engine idling, yet we know that the earlier low-side high pressure was around 350 psi. Something seems amiss.

The pressure discrepancy shouldn't be an issue. If I get a chance, somewhere I have an overlaid pt chart. It might be an issue on mechanical displacement control (based on suction pressure) but I can't see how it'd make a difference on the D3/4 system. The outside temperature and airflow would cause more pressure variation than the difference in PT curve for the different refrigerants.