Ac on my 7330 freezing

mhudgins · Jul 30, 2016

My Jd 7330 ac is freezing up when above 1200 rpms
Idling it will not freeze and hold 40-42 degrees in cab
But as soon as its throttled up it starts icing the low pressure line and eventually the evaporator
Pressure idling is 35 low side 175-180 high side
Any ideas what might be causing this
Thanks in advance
Matthew

Tx Jim · Jul 30, 2016

How clean is radiator,condenser & evaporator? How long since cab filters were blown out or new filter installed. What's the ambient temp where you live? 175-180 psi sounds low to me as my AC high pressure gets above 230 psi on a 95+° day

430WLPG · Jul 30, 2016

Sounds like the freeze switch at the evaporator is stuck and not letting the compressor cycle

mhudgins · Jul 30, 2016

82 degrees outside
Cleaned the condenser and evaporator
New filters 20 hrs ago

Lee B · Jul 30, 2016

You have a slow leak and it's finally caught up to you is what I'm thinking. Give us your low pressure at moderate throttle, if it gets too low it will freeze the evaporator and adding freon will make the low side pressure run higher such that it just won't freeze. You want 30 PSI low side at moderate to high engine speeds. Idle pressures don't really tell us anything other than reinforcing the symptoms that you are just low on freon at the moment. Freezing is 27.8 PSI but you can probably run as low as 25 PSI before the evaporator will actually ice over to stop air flow thru it.

mhudgins · Jul 31, 2016

It's less than 25 half to full throttle
But I've added to much trying to raise the low side
My high pressure is 350
So do you think my expansion valve is the problem
Even with my high side going that high the low is still staying around 30

Lee B · Aug 1, 2016

Yes, expansion valve is shot and needs replaced. You've found it about the only way one can find it when they fail in this mode too. You simply have to waste some freon to find the bad ones.

Double check for a clogged screen just prior to expansion valve though, sometimes this is the real issue and expansion valve is actually fine. Hoping it's not congealed stop leak on your screen.

4240 Turbo · Aug 3, 2016

Iagree, the low side or deice switch sounds failed. Should kick out pump before freezing occurs.

mhudgins · Aug 4, 2016

Changed out the expansion valve flushed entire system
Pull vacuum everything looked right
Fill it with amount of freon dealer told me and still same thing
On the parts page it shows a sensor with a probe is that the deicing part your talking about
Thanks for your help
Took the system apart to flush it

Ac on my 7330 freezing

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