AC unit freezes

[Madnance]

I have a 1993 J30T. I took it on some long drives in sunny calif the past couple of months and the AC always starts out strong, blowing good and nice and cold. But afer maybe 20-30 minutes, the volume of airflow drops and eventually gets to a very low level, like when the fan is set to minimum, though it is set to max. My brother said the condenser may be freezing, restricting air flow. So I tried setting it to "economy" when the problem re-ocurred thinking that this would turn off the AC and blow hot air across the condenser to melt any ice. Sure enough, this quickly brought the airflow back to a high volume, and the AC worked great when turned on again. But 20 minutes later I was back to the same problem.

Sure I can cycle it on and off myself but I thought I'd check and see if any experts know whats happening here and how I can fix it.

Thanks

[Q451990]

My first guess would be low refrigerant charge...

Heath

[maxnix]

And thus a leak that needs repairing. Might do a search on AC and learn how they should be maintained, or replaced if they are not.

[davehoos]

it will have a electric thermostat,it has fallen out of position,or no longer giving the corect resistance value.they also have an amplifier that fails regulaly.

I find on long runs the solid state electronics get hot and go ha wire.if it runs frozen the oil will gather inside the car and sieze/damage the pump.

on some nissans you can manhandle the evaporator out enough to get the new probe into positon. but probably a good time to clean out the junk inside the evaporator casing and service the airconditioner.

dave a/c specialist.