My 91 xj-s 12cyl has two electric fan's I installed a while back in order to replace the stock fan setup. They work with two speeds low comes on about 210F. I don't think high speed ever comes on except with the AC. It uses a simple radiator sensor to activate. Question:How can we get our X300 to just do a reliable basic job like the xjs in regard to these fans on slow speed all the time

 

The TSB does that in keeping the one left fan on at all times with key on

As Bob mentioned this keep the fuse from blowing if both fans come on at the same time in certain conditions

It does this by putting a jumper wire on the low pressure freon 2 wire switch

Some X300s do not have this low pressure switch installed but only the high pressure 4 wire switch and can be confusing

To do the mod yourself involves just cutting off the 2 wire connector and splicing the 2 wires together

This will use the the other path signaling the fan control relay module duplicating the coolant temp 2 temperature switch at the 86 C point and will work normally at the coolant temp of 100 C to give you both fans

This will also give you both fans under high A / C demand ( or high freon pressure ) and the oerpressure compressor cutout as originally designed with the 4 wire switch not disturbed or modified in the TSB mod

Keep asking questions

 

I grabbed a spare plug off a parts car. Wired it up as a loop. Now I can unplug old plug and put in jumper and fan runs from key on. Or I can plug old wiring harness back in and run as stock. I suppose I could leave out and only rely on the high speed fan once car gets warm but I think you risk overheat in traffic. I wouldn't disable all.