Kim,
Thanks for the pointers - i'll investigate the switches. This may be a side effect of pulling the dash apart to replace front heater core and fan - I did pull these switches at that time...
Thanks
Mike

Sent from my iPhone

On Aug 10, 2011, at 8:17 PM, Kim Brennan <kimbrennan@mac.com> wrote:

> Fan cutting out? That's not a freon issue. That's more indicative of a electrical issue. 3 possibilities occur to me. Thermostat switch (that which turns on the AC and sets the temperature. Speed control switch. That's the one with the 1-2-3-4 numbers on it. Wiring harness issue in the D pillar. 
> 
> If you have had condensation from the evaporator falling inside the cabin, then it is possible the condensation has made it into the wiring harness in the D pillar. This can lead to corrosion of the wiring, leading to resistance, leading to melting of connectors, etc. 
> 
> But an intermittent issue is most likely the first scenario. The thermostat switch is a rheostat (variable ohm resistor), which over time can age, and become loose. If it is loose enough it won't maintain the proper connections, and that could "turn off" the AC. 
> 
> 
> On Aug 10, 2011, at 9:47 PM, Michael Hart wrote:
> 
>> AC stops for a second or two. Just one time at first, now a few times in a row.
>> Blower fan stops then comes back on.
>> I rebuilt all hoses 2 years ago (kept to R12, new dryer, etc); system has blown cold ever since.
>> Is this a sign of low freon pressure or more likely a fan electrical fault? How to Diagnose? Late rear Westy factory AC system (87).
>> Thanks
>> Mike
>> 87 2WD Westy
>