Evap core freezing up?

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Just got back from a roundtrip to Memphis with my LR3. On the way back today, I noticed that after about 5-6 hours of solid driving with the AC on and recirc on, it didn't feel like there was the normal volume of air coming out. I turned off recirc (for the rest of the trip), and then turned the AC off for about 5 mins and then stopped for gas. It was perfect after that, lots of water was dripping out. Then again just as I neared home (about 5-6 hours later) it started feeling a bit clogged again. Temps where in the 80s most of the way and then in the 60s once I got back into Wisconsin. Is this normal? It was about 12 hours of continuous driving, with maybe 3 10 minute breaks to get gas. Never have driven that continuously before. AC still blew cold, as cold as ever. Seemed fine on the way there last week. Don't think it's low on charge. FWIW, it's never had AC work done and I've never swapped the cabin air filter. Is this something to worry about?

Thanks!
 
No expert here but I think you've diagnosed it. I wouldn't worry about it.
 
The LR3 has a high side pressure sensor and an evaporator temperature thermistor. It's a TXV with variable displacement compressor and a fairly impressive control system. If it iced up it should throw a code on the ATCM. Know anyone with a Ford T4 compatible scanner than can get a code from there?

If you've never had it re-gassed it would be worth getting the residual charge size measured, but I've got nothing else to contribute. With the control system that car has a plugged cabin air filter shouldn't be an issue.
If the charge was low enough to cause icing, it should be fairly noticeably impacting your day to day cooling though.
 
Dont know about a car but the evaporator core freezing in a house is usually a sign it is low on refrigerant.

Also check you cabin air filter, If it is clogged it could restrict the air flow.
 
Originally Posted By: Brad_C
The LR3 has a high side pressure sensor and an evaporator temperature thermistor. It's a TXV with variable displacement compressor and a fairly impressive control system. If it iced up it should throw a code on the ATCM. Know anyone with a Ford T4 compatible scanner than can get a code from there?

If you've never had it re-gassed it would be worth getting the residual charge size measured, but I've got nothing else to contribute. With the control system that car has a plugged cabin air filter shouldn't be an issue.
If the charge was low enough to cause icing, it should be fairly noticeably impacting your day to day cooling though.


That's what I was thinking about it being low...it should be warm. It's still very cold and if there's anything I notice in a vehicle, it's AC lol.
 
Forgot it had a cabin air filter till today and I'll look into the temp sensor. Thanks for the help so far, still listening to all of the advice!
 
Lack of airflow would probably result in the evaporator icing up as would a low charge. Cabin air filter would probably be easiest to check (depends on car really).
 
Usually it's caused from a lack of airflow. I'd check the cabin air filter and clean the housing where it sits out real good. I'd also check the condenser and make sure that's nice and clean, probably not the cause of the problem but often neglected. Next in line would be the refrigerant charge.
 
Lack of charge will not cause freeze-up in an auto system. They have different controls than home systems.
 
Going to change the cabin filter.

And it was in recirc for the first part, then I stopped using recirc and it still did it FWIW.
 
leave it out and if the problem persist then the filter is not the problem.

Where is the filter on you vehicle?
 
Originally Posted By: SHOZ
If the settings are in recirc the cabin filter is out of the equation.


+1

On most vehicles the cabin air filter only filters air that is coming in from outside of the vehicle. When it is on recirculate there is no air filter being used.
 
Originally Posted By: SHOZ
leave it out and if the problem persist then the filter is not the problem.

Where is the filter on you vehicle?


It's right above the blower motor, behind the glove box.

Just put in a new filter this morning. Not sure if it'll fix it, since I don't have any long trips planned for the rest of summer. May never know. LOL
 
When it's above the blower box where is the ducting that would be filtering recirculated air? On both my cars, if I remove the windshield cowling you can look and see the top of the filters from outside.
 
Originally Posted By: HoosierJeeper
Going to change the cabin filter.

And it was in recirc for the first part, then I stopped using recirc and it still did it FWIW.


Extremely low humidity can cause freeze up. On recirc for hours, there's definitely low humidity happening and potential for freeze-up. What warms evap coils is not only conducted heat from warmer air, but also the latent heat of condensation from humidity in the air. When humidity is very low, the condensate can freeze in layers, building up steadily as a white snowy ice on the coil. That white fuzzy ice has a terrible thermal transfer characteristic, effectively insulating the coil and ramping up the rate of icing. I find it somewhat difficult to completely thaw an iced coil; well not difficult but it it takes a much longer than expected time to thaw, again because of the insulating properties of the buildup. I suspect that when you switched to fresh air after the ice-up, the coil was not fully thawed and the ice, again, blocked full thermal conductivity to the coil driving the process once again. Whatever build up that did melt-off would explain the observed water pouring out of the condensate drain. If humidity is generally low outside as well, that wouldn't help the phenomenon.

One thing I'm not sure of is if refrigerant flow can be ceased all together with that VD pump or if there is always some small amount being pumped at it's minimum displacement. Perhaps the TXV is out of spec or it's temp sensor is not properly contacting the evap discharge pipe, system pressures incorrect etc. and so being unable to determine if the freeze-up can be prevented in a 'worst case scenario' like or if it should, by design, absolutely protect itself from such an incident. Evap freeze up is not that uncommon, though.
 
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