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Old 07-26-2010, 10:56 AM   #7 (permalink)
Master EcoModder
comptiger5000's Avatar
Join Date: Feb 2010
Location: CT, USA
Posts: 544

RaceJeep - '98 Jeep Grand Cherokee (ZJ) 5.9 Limited
90 day: 13.62 mpg (US)
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My Jeep has 2 thermo switches for the fan, 1 in the upper rad hose for low speed, one in the lower rad hose for high speed. Each switch kicks on at 210*, off at 207*. This leads to actual gauge temps of:

Low speed on: 214*
Low speed off: 211*
High speed on: 220*
High speed off: 217*

There is also a pressure switch in the A/C system to activate the fan on low speed when the A/C condenser isn't getting enough airflow to keep cool.

The fan on mine is the factory 16", 2 speed E-fan based off the Ford Taurus 3.8 fan and similar to the larger Lincoln Mark VIII 18" e-fan.

For yours, I'd say on at 210*, off at 205* would be a good starting point.
Call me crazy, but I actually try for mpg with this Jeep:

Typical driving: Back in Rochester for school, driving is 60 - 70% city
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