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Re: Jeep Wrangler Heater Fan
First, check for power (12v) at the fan plug. If you have power, the fan motor is shot. (replace it).You can "hotwire"the blower right to the battery to verify motor failure... don't forget the motor housing needs to be properly grounded or power is useless!! If no power, check the blower motor resistors (located on the firewall side of the heater box... usually looks like an oval flat plate with three or four wires connected to it. When removed, you will see two or three small coils: they should not be broken. Upstream from that you may need to look at the blower relay. Generally by the time you get to that, you have already solved the problem. If not, get a good wiring diagram before going further!
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Your cooling system works by getting air flow over the radiator and good circulation of coolant in the radiator as well as other areas of the motor.
The fan for your radiaror is electric, but it is designed to run at different speeds depending on conditions. First, I would verify that the fan DOES run. Sitting in the driveway with the engine at operating temperature, turn the A/C on and see if the fan speed increases right away or increases after running for 10 minutes. It should have a higher pitched sound. Look at the temperature gauge again and see if it is still at operating temperature. If the temperature continues to climb, turn the heater on full blast and watch the temperature gauge, it should drop.
No increase in fan speed means you could have a module problem or other problem related to the fan speed. In your relay box, relay "K11" is the fan relay. The relay box is in the engine compartment. The underside of the cover will identify what relays go for what. Some Jeeps used 2 relays, 1 for low speeds and the other for high fan speeds.The fan and module are replaced as a unit. The PCM (power control module is the brain for the engine management system including the controling of the fan relays. Sometimes the relays are the same and you can swap them with each other to see if there is a change. Note: If the temperature is normal when you are driving down the road, than the cooling system is normal and it is the fan.
Yes I would go with the switch, BUT, does it have a resistor bank? That is, how does it reduce the speed? Many systems use resistors to lower the speed. Burnt or bad connections can cause this as well.
You can test the blower motor by connecting direct power from a source like the cigarette lighter if you are handy.
Most of the time the lower speeds konk out but the high speed continues to work this is the resistor bank that goes out.
If you bypass the resistor pack and connect the motor directly to the fused 12v supply then the fan should run at maximum speed. If so, it's the resistor pack that's blown: a very common fault on a huge number of makes and models.
thats is two different problems. the blower motor resistor is bad causing it not to work on the lower setting just high. now on the defrost not working could be the blend door actuator but to figure it out you will need to be diagnosed by a professional. it is a little more involved. but the blower resistor is fairly easy
WELL YOU NEED TO CHECK THAT THE BLENDOORS ARE WORKING BUT OPEN HOOD WHEN CAR IS WORM TO RUNING TEMP FEEL THE HEATER HOSE THEY SHOULD BE HOT IF THEY ARE ITS MOST LIKELY BLENDOOR MOTOR OR BLENDOOR BROKE. HOPE THIS HELPS