Car overheated replaced thermostat/checked 30amp fuse to 78relay with wire fan came on. Is this meaning relay is bad due to fan came on?

Relays go bad, rarely. But it sounds like you already fixed this problem, now replace the bad relay ($25) and HVAC should work too?

FIRST OF ALL I WOULD REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP THEN CHECK SEE IF COOLING FAN RUNNING.WHILE CAR OVERHEATING. IF NOT CHECK COOLING FAN FUSE AND RELAY.IF ALL IS GOOD THE ENGINE COOLANT TEMPERATURE SENSOR COULD BE FAULTY.HOT WIRE SEE COOLANT FAN WORKS IF NOT, COOLING FAN MOTOR BAD NEED REPLACING.IF COOLING FAN MOTOR WORKING PROBLEM COULD BE IN FAN MOTOR WIRING OR PCM FAILED.

A bad relay will not blow a fuse. The radiator cooling fan must run with the A/C on or the vehicle will overheat and the A/C will perform poorly. First I would check the draw on you cooling fan motor-it may be blowing the fuse, or you have a wire shorted to ground.

temperature switch. The temperature switch finishes the circuit for the cooling fan. Once the engine reaches the specified optimal temp. the switch completes the circuit and turns the cooling fan on. Hope this helps

CHECK FOR LOW COOLANT LEVEL AND REPLACE THERMOSTAT AND THE RADIATOR PRESSURE CAP.IF CAR OVERHEATING AND COOLING FAN NOT WORKING.CHECK COOLANT FAN FUSE AND RELAY.IF BOTH OKAY,HOT WIRE COOLANT FAN,IF FAN WORKS, PROBLEM COULD BE FAULTY COOLANT TEMPERATURE SENSOR,OR FAULTY PCM, IF COOLING FAN DONT WORK WHEN YOU HOT WIRE FAN.THE COOLING FAN ASSEMBLY NEED REPLACING.

LOOK UNDER THE HOOD IN THE ENGINE COMPARTMENT. ON DRIVER SIDE FOR FUSE BOX.LOOK ON FUSE BOX COVER IT HAS LOCATION FOR FUSES AND RELAYS.MOST TIME PROBLEM WITH COOLING FAN CIRCUIT WILL CAUSE CHECK ENGINE LIGHT.BAD ENGINE COOLANT TEMPERATURE SENSOR WILL CAUSE COOLANT FANS NOT TO TURN CAUSE OVERHEATING. ON.REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP SEE IF STOP OVER HEATING. IF ALL LOOKS GOOD HOTWIRE COOLANT FANS MAKE SURE FAN MOTORS ARE GOOD AND NO SHORTS AT FAN CONNECTOR WIRES.

WHEN CAR STARTING OVERHEATING MAKE SURE COOLANT LEVEL DIDNT GET TOO LOW. IF NOT I WOULD REPLACE THERMOSTAT AND RADIATOR PRESSURE CAP IF OVERHEATING WHILE SITTING IDLING COOLING FAN NOT COMING ON.CHECK COOLING FAN FUSE AND RELAY IF ALL IS GOOD.CHECK COOLING BY HOTWIRING IT.IF RUNS YOU HAVE A BAD COOLANT TEMPERATURE SENSOR OR FAULT IN WIRE CIRCUIT.IF FAN DONT RUN WHEN HOTWIRED REPLACE FAN MOTOR.IF CAR STILL KEEP OVERHEATING CHECK ENGINE OIL LOOKS LIKE MILK BLOWN HEAD GASKET.IF OIL LOOKS OKAY YOU NEED RADIATOR AND ENGINE FLUSHED OUT.

before you think the thermostat is bad, first look in the fuse/relay box. lift the lid and look inside the lid for the correct location for the cooling fan fuse/relay. also if that is ok then unplug the cooling fan and use jumper wires to jump from the fan to the battery. if the fan runs then the relay maybe bad or the coolant temperature sensor may be going bad. rule of thumb if the car has run for awhile and got hot u can touch the upper radiator hose, if its hot then the water is circulating. if the upper hose feels cold then the thermostat is stuck open. replace the thermostat.

Don't rush to replace the fan itself until you have tested it. Check the fan relay and relay fuse inside the vehicle. Hopefully it will be just a failed relay and replacement ($12 at dealer) or/and an inexpensive 10amp or 30amp fuse. There can be multiple issues causing this code.

In my case, the fan relay failed (burnt). 2000 Dodge Durango. The PCM was also damaged and requires replacement, awaiting delivery. A remanufactured PCM can be purchased online for substantial less than at the dealer. We tested the fan by supplying power directly to the fan and it runs fine. We had to remove a cover (easy to remove) under the vehicle near the fan to gain access to the connector Use a fused link for testitng to prevent damage during the test. Using a multimeter, I found power 12.5volts from the 30amp fuse circuit which supplies the power for the fan, 12.5 volts from the PCM circuit with the key on, but only 5.16volts from the 10amp fuse circuit with the key on. A continuity test showed the 10amp fuse inside the fuse box inside the vehicle was good. The 30amp fuse in the power distribution box was good when tested for continuity. Checked resistance on all curcuits and they were well within limits. I also checked the wiring to the fan for continuity and resistance. After my tests were completed, a Dodge technican concluded the PCM is bad and is not grounding the circuit as it should. If you want to troubleshoot this yourself, see if your local library has access to ALLDATA which will have diagnostic information and the diagrams of the circuit involved. A Haynes manual for the vehicle, I purchased one at Autozone, can be helpful also.

the first thing to check is to have the engine running. as soon as it reaches operating temp the upper radiator hose should get hot. if it doesn't then it's the thermostat. if it does then i believe your water pump is probably not circulating like it should and it should be replaced. however before replacing the wter pump make sure that the wire to sending unit is tight and not giving you a false reading. if your model has electric fans make sure the fans are running when the engine is hot. if they are not running check the relay in the fuse box for the fans with the engine running switch out the fan relay with the a/c clutch relay. ifthe fans kick on replay the relay with a new one. if they don't click on the it's either a bad wire or the temp sensor probe is bad. hope this answers your question. please rate this solution...thanks.