Fan relay location for 1999 Jeep cherokee

Hi there:
DTC P1491 - RAD FAN CONTROL RELAY CIRCUIT

DTC P1491 is for the cooling fan relay control circuit as you've found already. Start by checking the fuse for the fan relay. Its in the box under the hood, a 40 amp fuse.

If you've got a couple jumper wires, you can unplug the fan connector and carefully jump the fan to see if it works. The fan connector is on the right side of the back of the fan shroud. Unplug it and jump the black wire to ground and the green to positive. You've got to be very careful doing this though-you are in very tight quarters, its not hard for your jumper wires to touch each other in the connector and short together, and if you use small diameter jumper wires they will get hot quickly when the fan comes on.

If the fan doesn't come on when you jump it, or if it runs slow or sounds bad, you've got a bad motor and will need to replace the fan assembly. One thing that does happen somewhat often, is a bad fan motor will burn up the relay. If the fan motor is drawing too much current it will overload the relay and burn it up. This is why its so important that if the fan motor runs slow or makes noise that you replace it, or you may end up burning up relays frequently.

If the fan runs and the fuse is good, its very likely you just need a fan relay. This is a pulse width modulated relay, not the on/off clicker type you'd find in the fuse box. This unit is capable of infinite speed control. It gets very hot in operation, so its mounted to the body sheet metal to allow heat to dissipate through the sheet metal. The relay is mounted under the right headlamp held down with two 8mm screws. To get to it you have to remove the front bumper cover and headlamp bracketry to access the relay. These relays are pretty common.

Check and test this possible causes:
radiator fan ctrl rly circuit wire harn intermittent defect
radiator fan ctrl rly circuit wire harn observable defect
radiator fan relay ground circuit open
rad fan relay control circuit open
radiator fan relay control circuit short to ground
rad fan control relay defective
PCM defective

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First thing you need to do is check the fan motor. You do that by unplugging the fan connector and hot wiring the motor to the battery. If it's good it will run.
The remainder of the system works this way: The temperature sender on the thermostat housing sends info to the computer which sends a ground signal to the relay in the power distribution center (or below the r/f headlight). the relay closes and sends power to the fan motor.
Computers rarely fail so you need to check the other components and wiring connectors.

cooling fan fuse should be third up from bottom on right on cabin fuse block. there may be another in power distribution center under the hood. Not sure if you mean radiator fan. to check, first hot-wire fan to battery. if it runs check fuse and relay. Radiator fan operates like this: coolant sensor sends signal to computer that sends ground signal to fan relay that then completes power circuit to fan. Difference in cabin fan is that the dash control sends signal to relay, then to resistor bloc, to fan motor.All electrical components require power and a good ground to operate properly.

Locate the relay in the under hood relay center remove it and swap it with the A/C relay or a relay that looks the same. If the fan still doesn't come on, the fan is not working anymore. If it does come on, go to the parts store and replace the relay. You can use a jump wire to the hot side of the fan from the pos side of the battery to see if the fan comes on. Also run a jump ground. Disconnect the harness to the fan so you don't back feed the ECM. Just use a couple of flat female blade connectors and wires to jump to the battery to test fan. $600.00 is way too much to replace the fan. You can find a good replacement fan assy. at the local wrecking yard for cheap. They work out just fine.

the only problem that vehicle has is with cooling fans is relay/module or electrical harness to module that burns up located behind and under right front headlamp assy must remove headlamp to access relay/module that is what powers up fan motor module assy.