Great advice, shawnlee.

Here's how I always wire radiator fans:



I would recommend using a trinary switch on the AC high pressure line to control the fan rather than just having it come on whenever the AC is on, or whenever the compressor is running.

If you already have a binary switch to keep the compressor from running if the pressure is too high or too low (most systems do, and all should), then the simplest way to do what you want is to replace the binary switch with a trinary switch. The compressor section of the trinary switch will be wired to the same wires as the binary. The additional two wires on the trinary switch (the fan section of the switch) can simply be wired in parallel with your over-ride switch...assuming that in your case the over-ride switch trips the relay in the thermo switch instead of bypassing it. Otherwise kindly disregard this paragraph, and use the trinary switch fan section to trigger your new fan (AC) relay.

Sorry I'm not familiar with the integrated switch/relay you speak of. I typically just install an OEM radiator fan switch (Standard Ignition TS-87) in the lower radiator tank and wire it per the above diagram.

Hope this helps....