Question about 1999 Jeep Grand Cherokee

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A/C Fan blow on high setting only.

There are four setting on the A/C fan control panel. 1,2,3 and 4. The only one that works is 4. So either the fan doesn't blow at all or it blows on the highest setting. What should I be looking for?

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It's most likely a bad switch. You could go to a car junk yard and find a switch unit there for cheap. The hardest part would be installation.

Posted on Jan 05, 2009

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Need a wiring diagram of the 2 wires from the temp sending unit that controls the temp gauge and cooling fans on a 99 grand am gt. Need to see where they go They disappear behind the engine


The PCM regulates voltage to the coolant fan relays, which operate the fans. Refer to Engine Controls.

Engine Cooling Fan Description - Electric
The electric cooling fans are used to lower the temperature of the engine coolant flowing through the radiator. They are also used to cool the refrigerant (R-134a) flowing through the A/C condenser.
Operation
The electric cooling fan operates when the engine cooling temperature exceeds a certain value. The cooling fan on this engine is controlled by the PCM. The cooling fan has one speed. The PCM turns the cooling fan ON by grounding the coil of the cooling fan relay when certain conditions are met. When the A/C is requested, the cooling fan will also be turned ON.
Power for the cooling fan motors are supplied through Cool Fan #1 and Cool Fan #2 relays. The cooling fan relays are energized when current flows from the fuses in the Cell 23: Cooling Fan Controls , and through the relay coils to ground through the PCM. The Low Speed fans control circuit is grounded for low speed fans operation. During low speed fans operation, both fans run at a slow speed. The High Speed fans control circuit is grounded for high speed operation. During high speed fans operation, both fans run at high speed.
Important: When certain Diagnostic Trouble Codes (DTCs) are present, the PCM may command the cooling fans to run all the time. It is important to perform Powertrain On Board Diagnostic (OBD) System Check prior to diagnosing the engine cooling fans.
If a problem that involves the low speed cooling fan relay control circuit exists, DTC P0480 should set. If the problem affects the high speed cooling fan relay control circuit, DTC P0481 should set. A problem with the ECT sensor should set DTC P0117, P0118, P1114, or P1115. Any of these DTCs will affect cooling fan operation and should be diagnosed before using the Cooling Fan Diagnosis tables. The Cooling Fan Diagnosis tables should be used to diagnose the PCM controlled cooling fans only, if a DTC has not set.

The engine coolant temperature (ECT) sensor (3) is a thermistor, a resistor which changes value based on temperature, mounted in the engine coolant stream. Low coolant temperature produces a high resistance (100,000 ohms at -40°C) (-40°F), while high temperature causes low resistance (70 ohms at 130°C) (266°F).
The PCM supplies a 5 volt signal to the ECT sensor through a resistor in the PCM and monitors the terminal voltage. Since this forms a series circuit to ground through the ECT sensor, high sensor resistance (low temperature) will result in high PCM terminal voltage. When the resistance of the ECT sensor is low (high temperature), the terminal voltage will be drawn lower. This terminal voltage indicates engine coolant temperature to the PCM.
A hard fault in the ECT sensor circuit should set either a DTC P0117 or P0118. Remember, these DTCs indicate a malfunction in the engine coolant temperature circuit, so proper use of the DTC table may lead to either repairing a wiring problem or replacing the sensor, to properly repair a problem.

The engine coolant sensor is an input to the PCM , Two wire's both go to the PCM .An the PCM turns on the cooling fans !

DTC P0480 Cooling Fan Relay 1 Control Circuit
DTC P0481Cooling Fan Relay 2 Control Circuit
The Body Control Module (BCM) request the cooling fans. The BCM sends a Class 2 message to the PCM in order to enable the fans based on various inputs. Thebattery voltage travels to all three cooling fan relay coils. The PCM enables cooling fan relay #1 by providing the ground path. The PCM enables cooling fan relays #2 and mode control together by providing a ground path. The left and right cooling fans are connected in series. This will enable both fans on low speed when the fan #1 relay is energized. When all three fan relays are energized, both fans will operate at high speed. The high speed is possible because the fan relays are wired in a parallel circuit. When the PCM detects that certain DTCs are set, the PCM will enable the cooling fans.
The PCM will enable the engine cooling fans when certain Diagnostic Trouble Codes are set.

Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1
Did you perform the Instrument Cluster System Check?
--
Go to Step 2
Go to Instrument Cluster System Check
2
Turn the ignition switch to the ON position.
With the scan tool select Instrument Panel Cluster, Special Functions, Instrument Panel Cluster (IPC) gauges.
Perform the Coolant Gauge Sweep Test.
Does the coolant temperature gauge complete a full sweep when commanded?
--
Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls
Go to Step 3
3
Replace the instrument cluster. Refer to Instrument Cluster Replacement .
Did you complete the repair?
--
Go to Instrument Cluster System Check
--

Your best bet would be to take your vehicle to a qualified repair shop that knows how the system works . An has the tools to diagnose the problem .

Nov 13, 2016 | 1999 Pontiac Grand Am GT

1 Answer

2011 Nissan Titan heater/ac fan blows on high we replaced the VBC it did not fix it, now what?


What is VBC? Ah, probably Variable Blower Control? my guess you got wires crossed, or a short around the control or even direct short to hot (12vdc) wire. Double check your work, wire connections. Instructions? with the new? double check.

Feb 27, 2015 | 2011 Nissan Titan Crew

1 Answer

Have a 2009 Nissan Quest I can't turn the heat off. Just stays on a high level of blowing out heat .


If you have a fan that has different speed settings (1234, or low med high etc) and the only one that works is high - then the blower resistor pack has failed. If you have a climate control unit (where you just pick a temp you want) then the fan is controlled by the heating system and it sets fan speed. If you have climate control style try lowering the temp to a lower setting (current temp in vehicle) and see if fan slows down. If not then climate control unit or fan resistor bad. If dial type and you get nothing on lower settings (only high works like mentioned above) you need to change blower resistor. It is located under dash near the fan itself. Look for small unit bolted in duct near fan with wire plug going to it.

Feb 23, 2015 | Nissan Cars & Trucks

1 Answer

Why wont my a/c or heater fan come on?


When the blower works only on the high setting its usually a bad blower resistor which is right near the blower motor. now you say it would always blow high regardless of the fan speed setting that would indicate probably the climate control unit or a connector problem somewhere. finally it not working at all may be the climate control unit or connection went bad even further. it might have a blown fuse or a bad blower motor in addition to the climate control unit or connector problem .check for power and ground at the blower motor. the power is supplied from fuses and may have a relay also. the ground is supplied from the climate control unit and goes through the resistor to control the fan speed. good luck

Oct 30, 2011 | 1997 Lincoln Continental

1 Answer

Fan which blows heat doesn't work when toggle at dash board is moved to high.


When your fan switch is placed in the high position, it feeds directly to the fan motor and bypasses the blower motor relay. If the fan is operating on speed 1-3, then you have one of two things wrong, either you have a blown fuse, or the fan selector switch is faulty on the high setting.

Mar 29, 2011 | Geo Tracker Cars & Trucks

1 Answer

The blower on the fan is stuck on high...we have taken the fuse out and checked it...not the problem...we then took the climate control unit out and unplugged them, but the fan kept blowing on high...is...


This is most likely the Blower Motor Resistor located near the Blower Motor. This controls the Fan Speeds. Usually when these fail it will only work on the High setting, meaning it does not work on settings 1 or 2 or 3 (with four speed setting). This usually located behind the dash Glove Box and mounted on the fire wall . You will need to take the Glove Box out to access. It is approx 3 1/2 inches wide by 1 1/2 inches in height. It is defined with 3 or 4 wires going into it. It is easy to remove (two (2) 8mm bolt/metal screws) and replace. Purchase the part at the auto parts store versus at the dealer to save you a lot of money.
Let me know if this helped, or if you have additional information or questions. Feel free to contact me at FixYa.com!

Jan 23, 2010 | 2003 Chrysler Town & Country

1 Answer

Only have 1 speed on HVAC fan


the fan relay(resister) that control fan speed is probably burned out.When this occurs it will only blow at high speed because its getting 12volts directly to the fan

May 25, 2009 | 2004 Pontiac Vibe

1 Answer

Fan speed only works on #5


Is # 5 the high setting ? if so then you blower motor resistor is bad

Jan 11, 2009 | 2000 Pontiac Grand Prix

1 Answer

Heater only blows hot (well, warm) on full speed of fan


Replace the temp control on this car, it should be electrical control not cables.

Dec 03, 2008 | 2000 Ford Escort

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