I did a 2 fan conversion on my jeep and loved it, manual switches, upgraded to 105 amp alternator. Its very high on my 'to do' mod list for my TD. Faster warmups, extended cooling possibilities after engine shut-down. 2 (or 3 if you includer the OE electric pusher fan) fans for redundancy. Absolutely worth it IMHO.

If I was going to install an automatic thermostat for the fan(s), I'd set it high... the oil cooler thermostat doesn't even open till 90+ degrees... no reason the fan should be spinning if the oil cooler isn't in effect.

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Cheers,
Robert