[MachoSwede]

This is what happened - car got hot - fans not working.

One fuse inside car melted - changed it - no fan.

Took the car to my garage - took relays and fans off and checked.

Both fans run direct connected to battery - fan relays OK.

Thus must be a communication problem - radiator guage OK.

Thought of swapping temp sensor - but very very hard to get access to.

Pondering and decided to buy either the Pantera PWM fan controller or
Auto Cool Guy's PWM Fan Controller - bought ACGs - problem solved.

This is the result - adjuste knob to fully hot - compared to original fans start
earlier but run slower - fans don't start until guage i in the middle - original
often started or run full speed one step above middle.

Anyone with similar or different experience - how to swap the temp sensor easiest way?

 

[Submariner409]

On the first, second, and third Northstar series the thermostat is set to begin opening at 188 degrees F and fully open at 206. Fans did not go to SLOW until 224 degrees and fast at 236 degrees. Fans ran in SLOW any time an A/C compressor function was set. Fans did not run at over 30 - 35 mph - not needed. A Northstar with correct cooling system operation runs at 190 - 205 degrees all day, every day and fans would not then run.

Is the coolant purge line cler and flowing a small stream at idle?

The center "12 o'clock" gauge mark is right in the middle of the normal temperature range and fans should NOT run there.

Study all the cooling system sticky threads in Engines; Northstar.

Here's a 2000 temp gauge with annotated markings. Fans go to SLOW at the yellow mark, FAST at the red.