Jeep Grand Cherokee Cooling Fan Relay: Identification and Location
On most Jeep Grand Cherokee models, the cooling fan relay sits in the underhood power distribution center. Its exact position, and whether a separate replaceable relay exists at all, depends on model year, engine and the type of electrical module fitted. This guide explains how to find and identify the relay, how the fan circuit works, and how to check it without confusing a relay fault with a fuse, wiring, fan motor or control problem.
Where the cooling fan relay is located
Look for the black plastic fuse and relay box in the engine compartment, usually near the battery or along one side of the engine bay. Depending on the generation, Jeep calls it the Power Distribution Center, the Totally Integrated Power Module or the front power distribution center. The underside of the lid normally carries a map showing each fuse and relay position, and the owner's manual has a matching chart. The fan relay may be labeled radiator fan, cooling fan or fan high/low, and two-speed systems can have more than one fan relay.
Two exceptions matter. On some integrated power modules, certain relays are soldered onto the internal circuit board, so there is nothing to unplug and replace separately. Some later Grand Cherokee configurations use an electric fan with its own control electronics, powered through a high-current fuse and commanded by the engine computer. On those vehicles, the fan speed decision is made inside the fan module, not by a conventional plug-in relay.
How the fan relay circuit works
A relay lets a small control current switch a large load. The coil side is controlled by the engine computer, which typically completes the coil circuit to ground when cooling is needed. When the coil energizes, the contacts close and send fused battery power to the fan motor. On a standard mini relay, terminal 30 is the power feed, 87 is the output to the fan, and 85 and 86 are the coil terminals, but always confirm terminal functions against the wiring diagram for your vehicle.
The engine computer decides when to run the fan using inputs such as coolant temperature, A/C refrigerant pressure and vehicle speed, and on some models transmission temperature. That is why the fan often runs with the A/C switched on even when the engine is not hot. Some vehicles also keep the fan running briefly after shutdown, so a fan that starts with the key off is not automatically a fault.
What changes by generation and powertrain
Not every Grand Cherokee depends mainly on an electric fan. Some older versions use an engine-driven fan with a viscous clutch, sometimes supplemented by an electric fan for A/C or towing duty. On those, overheating at idle may point to the fan clutch rather than any relay. Engine choice, towing packages and trim level can change the number of fans, their wiring and their relay arrangement within the same generation.
The plug-in hybrid 4xe adds a high-voltage traction battery and related cooling systems alongside the conventional 12-volt starter battery. The fan relay and fuse box belong to the 12-volt system, but the vehicle also carries high-voltage components marked with orange cables. Treat these as two separate systems: disconnecting the 12-volt battery does not de-energize the high-voltage circuit.
How to identify and check the relay
Start with the simplest observations. With the engine running and warmed up, switch the A/C to maximum and watch whether the fan engages. If it never runs, check the fan fuse first, using the fuse box map. If a fuse has blown, replace it only with the same fuse rating, because a larger fuse can let a shorted fan motor or chafed wire overheat. A fuse that blows again points to a fault in the motor or wiring, not the relay.
If the relay is a removable plug-in type, compare the part number printed on its case with another relay in the same box. Where an identical relay serves a non-critical circuit, swapping the two is a quick test. If the fan starts working and the other circuit stops, the relay is faulty. You may also feel or hear the relay click when the A/C is switched on or when a scan tool commands the fan.
With a multimeter, check for battery voltage at the power-feed terminal of the relay socket, then confirm that the coil receives power and a ground command when the fan should run. A voltage drop test across the closed contacts while the fan is running shows contact resistance. More than a few tenths of a volt suggests worn contacts or a poor socket connection. Bridging the feed and output terminals to run the fan directly is a valid test only on a conventional relay circuit, only when the wiring diagram confirms the terminals, and only with a fused jumper rated no higher than the circuit fuse. A relay can also fail with its contacts stuck closed. The fan then keeps running after shutdown and drains the battery. If the battery goes flat overnight and you can hear the fan, a parasitic draw test with an ammeter at the battery terminals will confirm the drain, and pulling the fan relay should stop it. Weak charging output or low system voltage can also make a fan run slowly, so verify the battery and charging system before condemning the fan.
Working safely around the fan and batteries
Keep hands, tools and loose clothing away from the fan blades whenever the battery is connected, because the fan can start without warning, even with the ignition off. Before unplugging the fan connector or repairing wiring, disconnect the negative cable from the 12-volt battery terminals. On some generations the battery is not under the hood, so follow the owner's manual for its location and for the use of any remote jump terminals.
On a 4xe, limit owner work to the 12-volt fuse box and accessible 12-volt components. Do not unplug, probe or cut any orange cable or high-voltage component. Isolating the traction system requires the manufacturer's high-voltage disable procedure, appropriate insulated equipment and training.
Limitations and next steps
Relay positions, terminal assignments and fan control strategies differ across Grand Cherokee generations, so no single diagram fits every vehicle. For accurate testing, use the fuse box label, the owner's manual and a wiring diagram matched to your VIN, model year and engine. A scan tool that reads trouble codes and can command the fan saves considerable guesswork, especially on vehicles with integrated relays or electronically controlled fan modules.
Stop driving if the temperature gauge climbs toward the red, because overheating can damage the engine quickly. Seek professional help if the relay is integrated into the power module, if the fan module or engine computer is suspected, if wiring damage is hard to trace, or if any high-voltage component on a 4xe may be involved.