heater blower motor

yes it is called the blower motor resistor (called the blower motor controller on schematics) most likely that is your problem but I'm sending you the diagnostics procedure just in case you need it

This guide cane help us fix it.

https://www.2carpros.com/articles/blower-fan-motor-works-on-high-speed-only

1999 Jeep Grand Cherokee 4.0L Eng Laredo
Vehicle Reference: HVAC SYSTEMS - AUTOMATIC
SYMPTOM DIAGNOSIS > BLOWER MOTOR INOPERATIVE

Possible causes: blower motor controller ground circuit open, Power Distribution Center (PDC) fuse No. 1 blown, defective blower motor. blower motor voltage supply circuit open/shorted to round, blower motor control circuit open/shorted to ground, blower motor controller defective, defective AZC module (no PWM signal), defective AZC module (PWM signal sent, blower high), blower motor control circuit shorted to blower motor ground circuit, or blower motor control circuit shorted to B+ (battery voltage).

Turn ignition off. Remove and inspect Power Distribution Center (PDC) fuse No. 1. If fuse is blown, replace fuse and check for a short circuit. If fuse is okay, go to next step.
Disconnect blower motor controller connector. Check connector and repair as necessary. Measure resistance between blower motor voltage supply circuit and ground. If resistance is less than 5 ohms, repair short circuit to ground. Calibrate HVAC system. See BODY VERIFICATION TEST VER-2A under PROGRAMMING. If resistance is greater than 5 ohms, go to next step.
Turn ignition off and disconnect blower motor. Using a known-good battery, apply voltage directly to blower motor. If blower motor runs properly, go to next step. If blower motor is inoperative, make sure blower motor is not obstructed. Repair or replace blower motor as necessary.
Disconnect blower motor controller. Check connector and repair as necessary. Measure resistance between ground and blower motor controller ground circuit. If resistance is less than 5 ohms, go to next step. If resistance is greater than 5 ohms, repair open ground circuit.
Turn ignition on (engine off). Ensure blower switch is off. Disconnect blower motor controller. Check connector and repair as necessary. Rotate mode selector switch to defrost position, turning front defroster on. Rotate blower switch to high (manual override). Check voltage at blower motor voltage supply circuit. If voltage is greater than 10.0 volts, go to next step. If voltage is less than 10.0 volts. repair open blower motor voltage supply circuit. Calibrate HVAC system. See BODY VERIFICATION TEST VER-2A under PROGRAMMING.
Turn ignition off and disconnect blower motor. Disconnect AZC module connector. Check connectors and repair as necessary. Measure resistance between blower motor control circuit and ground. If resistance is less than 5 ohms, repair short circuit to ground. Calibrate HVAC system. See BODY VERIFICATION TEST VER-2A under PROGRAMMING. If resistance is greater than 5 ohms, go to next step.
Disconnect blower motor controller connector. Disconnect AZC module connector. Check connectors and repair as necessary. Measure resistance of blower motor control circuit between blower motor controller and AZC module C2 connector. See WIRING DIAGRAMS . If resistance is greater than 5 ohms, repair open blower motor control circuit. If resistance is less than 5 ohms, go to next step.
Turn ignition off. Disconnect blower motor controller connector. Check connector and repair as necessary. Turn ignition on. Measure voltage between ground and blower motor control circuit at blower motor controller 3-pin connector. If voltage is greater than 0.5 volts, repair short to battery voltage in blower motor control circuit. Calibrate HVAC system. See BODY VERIFICATION TEST VER-2A under PROGRAMMING. If voltage is less than 0.5 volts, go to next step.
Turn ignition off. Disconnect blower motor controller connector. Disconnect Heater Ventilation A/C (HVAC) body harness connector (C202). Check connectors and repair as necessary. Measure resistance between blower motor control circuit and blower motor ground circuit. If resistance is less than 5 ohms, repair short to ground in blower motor control circuit. Calibrate HVAC system. See BODY VERIFICATION TEST VER-2A under PROGRAMMING. If resistance is greater than 5 ohms, go to next step.
Turn ignition on. Using DRB lab scope, select LIVE DAT, AUTO SET-UP, set the TIME DIVISION to 20MS/DIV. Set voltage range to RANGE±10.0 VOLTS. Backprobe blower motor control circuit at blower motor controller 3-pin connector with blower motor switch in LO (manual override) and mode select switch in defrost mode.

The voltage pattern should cycle from about 0.5 volts up to 5.0 volts in low speed fan position. If voltage pattern is cycling as specified, go to next step. If voltage pattern is not cycling as specified, replace defective AZC module.
With lab scope as in step 10) , backprobe blower motor control circuit at blower motor controller 3-pin connector with blower motor switch in HI (manual override) and mode select switch in defrost mode. The lab scope pattern should be flattened.

Now change the lab scope voltage setting to RANGE±2.0 VOLTS. The voltage pattern should cycle up to about 0.3 volts with blower motor in high fan speed. If voltage pattern is as specified, go to next step. If voltage pattern is not as specified, replace AZC module.
Disconnect blower motor. Check connector and repair as necessary. Turn ignition on. Place blower switch on HI and mode selector switch to defrost mode. Connect a test light across blower motor wiring harness 2-pin connector. If test light comes on brightly, test is complete. If test light does not come on brightly, replace blower motor controller.

My heater worked before and now all of a sudden it does not (checked fuse) it was blown, changed and it just blows right away. checked blower motor it does work. I took the dash apart to check into it further.I have the (auto climate control), so now I have climate control out, resister out, and blower motor out. I go to put a fuse in and it blows (10amp), I have checked the 3 wires for current all are good, red, black, brown/white. Please help.

Good afternoon.

I attached a diagram for the fuse. It should be fuse 12 in the junction block which is 10 amp.

https://www.2carpros.com/articles/how-a-car-fuse-works

There are many components it controls. Disconnect all these components and see if the fuse still fails. If it does, it is a short in the harness. If it does not, plug one component in at a time until it fails. That will tell you the area of failure.

Roy

okay, so question, from your diagram, does the seat heaters work of that 10 amp fuse also?

Correct, It supplies power to the seat switch.

Roy

Replaced the climate controls, the fuses are good and the blower fan is not working. What do I check next?

Check your blower motor resistor. Have seen the ground wire burn up at the connector. If it is burnt then replace the resistor and splice in a new connector.

okay, thank you. i will unplug them as i don't use them any ways and will get back to you with a reply.

Sounds like a plan.

Roy

Hi Roy, i unplugged the seat heater switch at the switch, actually i unplugged the entire unit in the dash and it still blows the fuse.

There were several components that were covered by that fuse. You need to unplug all of them and then test.

Roy

From your diagram the only thing that is not needed for the heater/blower is the heated seats, i unplugged the unit with these controls in the unit (heated seats, rear defrost, over drive,rear wiper) and it still blows the fuse.

Okay, that's good.

Then you have a short in the harness somewhere. Finding a short is never fun and time consuming opening the harness and following it.

https://www.2carpros.com/articles/how-to-check-wiring

It might be good to get some help on this issue.

Roy

i started at the PCM under the hood and checked the wire to inside the vehicle and then checked the wires inside the vehicle (every wire shows current).

It takes a long time to unwrap harness. Did you unwrap the harness?

You are not checking current, you are looking for wiring damage. It would be wires touching together somewhere.

It will be between the control head and the blower motor, not the PCM.

Roy

No i did not, i was just checking for current (electrical is not my strong point), lol. so are you saying a wire is damaged in that area and either grounding out or ground wire touching something live?

Correct.

Roy

okay, this is where i am confused as it worked fine before.

My 1993 Grand Cherokee's heater blower motor quit working, so I assumed it was the motor. I replaced the blower motor, but it still didn't work. So I replaced the resistor, and still nothing. What should I check/do now? Thanks.

here's diagram

That is why I questioned about the way you wired the connector.

Roy

Thanks. Turned out to be the blower motor fuse, it had burned out.

i didn't wire a connector, it just stopped working all of a sudden. so i checked fuse and it was blown and keeps blowing fuse as soon as i even touch it to put the fuse in.

Check the connector for the correct wires to the resistor.

Roy

Okay, sounds like you have a short in the harness.

Roy

if this is the resister block at the blower motor the wires i have at the plug are (red, black, and tan with white stripe).

another question would be is, would the Air Door Actuator have any power without the heater being on or blowing the fuse? since i have all of the other heater units disconnected and it still blows the fuse.

The power to the actuator comes from the control head. Disconnect that as that is part of the fuse control.

Roy

okay, i have the control head out, the control module out, the blower motor out and the heated seat /overdrive/rear window defog out and still blows fuse and you say its a wiring between control head and control module...is that correct??

this is the control module. am i correct??

No, that is the blower resistor.

The control head is the control assembly on the dash board.

Roy

okay, so the power comes from the control head. hence why you said it will be between the control head and the blower motor.

If the fuse does not fail after you disconnect the control head, yes.

Roy

okay, yes it failed. i have the control head out. the blower motor and the resister out and the seat control unit out and it still fails.

how do these come undone?

Okay, you have a wire harness issue somewhere in the harness.

It will be a time-consuming job to uncover the harness and look for bad wires.

https://www.2carpros.com/articles/how-to-check-wiring

Roy

i have unraveled all the tape, i see nothing that indicates a short or bad wire, not even sure how the fuse box comes off. can i not just run power from a empty fuse? (already frustrated)

Yes, you can do an overlay but you need to cut out the bad wire so it has no power and then run new wires to all the components it powers.

Roy

how does the fuse box come off??

I posted the procedure and a couple of pictures.

Roy

(1)Disconnect and isolate the battery negative cable.

(2)Remove the fuse access panel by unsnapping it from the right cowl side trim panel.

Right Cowl Side Trim Remove/Install
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(3)Remove the nut securing the right cowl side trim to the junction block stud.

(4)Remove the two screws securing the right cowl side trim to the right front door opening trim.

(5)Remove the right cowl side trim panel.

(6)Unplug all of the wiring connectors from the junction block cavities.

Junction Block Remove/Install
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(7)Remove the junction block mounting bolt.

(8)Lift upwards on the junction block to remove its slide-tab mount off of the mounting bracket on the right cowl side panel.

(9)Remove the junction block from the vehicle.

(10)Reverse the removal procedures to install.