AC freeze up, 2003 quad cab

[TObrien]

My AC freezes up occasionally, mostly in slower traffic but sometimes on hiway. Usually when blower fan is set to slower speed. If i turn up the fan speed I can hear the fan trying to push air, but next to nothing comes out of the vents. If i leave the fan going and defeat the AC, it will get back to normal blower flow in a few minutes, then the cold air warms up to ambient- I'm guessing there's an ice dam building on the heat exchanger that melts away after the AC is turned off. When I engage the AC again it will repeat the problem in 15 - 20 minutes. I get good condensate drainage, It continues to drip even after the ice dam builds. Is there a freeze-up sensor somewhere in the enclosure which I can check? Thanks for the help.

 

[CBari]

Mine did the same thing for about a year till I read a post about someone else's doing the same thing. The fix was to add a little freon. I added less than a half a can of freon and mine has been fine ever since.

 

[Lumpy]

Sounds like your ac system is low on refrigerant, or the orifice tube in your receiver drier is plugged. I'd start with adding freon first. That's solved the problem in most of the dodge truck that I've came across.

 

[The patriot]

It could also freeze due to inadequate flow.
Turn the fan up one notch.

 

[TObrien]

Thanks guys, I'll try the freon. Don't understand why LOW freon would cause the freeze though? And I probably won't need AC until next year up here in CT, so testing will be delayed! Thanks again.

 

[Hitec.Redneck]

The low pressure switch can be bad also, it will let the compressor run until things freeze up.

 

[Lumpy]

The evaporator coil could be full of crap too. Not enough airflow= Freeze.

 

[The patriot]

It could also freeze due to inadequate flow.

Turn the fan up one notch.

Yup.

 

[rscurtis]

Thanks guys, I'll try the freon. Don't understand why LOW freon would cause the freeze though? And I probably won't need AC until next year up here in CT, so testing will be delayed! Thanks again.

Modern auto AC systems use the bare bones of controls to enable them to work- just like a home dehumidifier. Thermostatic expansion valves and suction throttling valves are long gone. When the refrigerant charge is low, the evaporator pressure (and temperature) drop below freezing, leading to your icing.

 

[TimothyLong]

I'm thinking it's low on freon as well. Back at the end of June, my home AC froze up. Called the HVAC guys and they ended up putting 3 lbs. of freon in the system. It's been fine ever since.

 

[Bill Stockard]

Modern auto AC systems use the bare bones of controls to enable them to work- just like a home dehumidifier. Thermostatic expansion valves and suction throttling valves are long gone. When the refrigerant charge is low, the evaporator pressure (and temperature) drop below freezing, leading to your icing.

Yep, the orifice tube eliminated the moving parts making it a more simplified system. My first enconter with the orifice tube system was when GM made the big body change in the '73 pickups. I can tell what happens when the orifice tube is blocked with debris from a failed receiver/dryer and the high pressure relief valve fails to open in time. I thought the engine blew up and the truck was on fire!



Bill