This is how I have decided to wire the fans on my Monza. Someone may find it useful.
Power flows from an ignition source through a diode wired in series with the fan temp switch. When the engine reaches temp. the switch closes and energizes two small Bosch style relays. The normally open contacts handle the fan motor current load. A second diode feeds power from the A/C system to bring on the fans if they are not yet running and the a/c is turned on. This ensures air flow across the condensor and prevents a hi pressure cut out situation.
The first two diodes isolate the two sources to prevent any backfeed.The other two diodes across the relay coils are for noise suppression. Any small silicon diodes rated for at least an amp will work.
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