I've had that high speed fan come on in a couple of instances.  It makes
for a nice foot massage.

Geo/ATL

On Sun, May 19, 2013 at 3:45 PM, David Beierl <dbeierl@attglobal.net> wrote:

> At 12:47 PM 5/19/2013, george jannini wrote:
>
>>   Should I put mr. resistor on my list of "spare crap I always need to
>> carry with?    :-)
>>
>
> The fan in an A/C 2.1l Vanagon has three speeds:
>
> a) Low speed from the rad thermoswitch (paralleled by the A/C relay)
> through both parts of the resistor to the fan.
>
> b) Middle speed from the A/C high-pressure switch through the A/C fan
> relay and one part of the resistor.
>
> c) High speed from the rad thermoswitch through the rad fan relay straight
> to the fan.
>
> As long as the thermoswitch AND (either both sides of the fan resistor OR
> the relay) are working you've got a radiator fan.  If the thermoswitch dies
> you can fake it by turning on the A/C with temp set to maximum.
>
> Normal A/C operation sequence:
>
> a) Radiator fan runs at low speed whenever system is on, A/C ups it to
> second speed if the high-side pressure rises too far.
>
> b) Compressor clutch will engage if ambient temp >/= 5C/41F AND rad
> thermoswitch first speed not active (indicating that the first-speed fan
> can't keep up with the load and the system is heading toward high-speed
> operation).
>
> There's a good deal of redundancy.  I don't think you'd need to carry a
> spare normally.  But the backstop spare would be the radiator fan relay for
> the high speed, if you were going to carry one thing.
>
> Note: this doesn't take the A/C system itself into consideration.  There's
> no high-pressure shutoff on the compressor, only the mid-speed fan.
>  Perhaps the answer is inspect the resistor and replace if it's
> deteriorating.
>
> Yours,
> David
>