c5 a6 ac and fan issue

[chris.miller]

1999 wagon with the two terminal resistor block under the driver's frame rail controlling fan speeds.
AC working great and cold then nothing. No electric fan operation.
Jumped power to the fan and it runs but getting noisey.
Pulled under dash cover and fuses appear intact.
Not sure which of the many relays under there control the fan speed.
Ran HVAC codes and I get a 00792 a/c pressure switch error (F129).
Unplugged and reconnected switch and no change.

• Indicates a short circuit to ground
• Open circuit in wiring between a/c pressure switch and a/c control head
• activation of coolant fan V7 (step 2) from a/c pressure switch malfunctioning
• a/c pressure switch faulty
• malfunction in a/c coolant circuit (positive or negative pressure)

If I clear code with ignition on engine off code immediately resets so I don't think it is a problem with actual pressure in the a/c system.

Before I dig in further, any suggestions?
Chris

[chris.miller]

Oh, and I did the output test by pulling the radiator temp sensor connection and bridging terminals; both low speed and high speed fan operation works.

[chris.miller]

Related question. Can I pull the high pressure switch off the condensor without losing refrigerant? I see posts about an o-ring and shraeder valve.

[chris.miller]

More follow up.* Unplugging the F129 switch has no effect.* Jumpered pins one and two and the compressor clutch engaged and low speed fan operated.* Jumpering pins 3 and 4 and fan goes to higher speed.

However, a couple minutes with the compressor running and the system doesn't cool at all.* I'm suspecting a massive sudden leak in the system; blown out o-ring?

[AR15Texan]

Can you get manifold gauges on it to check system pressures? Inspect the condenser for road debris damage. Why is the fan noisy?

[Moredooravant]

Fo you have a part number or actual name for that
Two terminal resistor block under the driver's frame rail? Mine is crusty and I had a fan failure. I'd like to find a replacement