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Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Jeep
Satisfied Customers: 1524
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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2000 Grand Cherokee GC Limited: Can u help with a grand Cherokee

Customer Question

Can u help with a grand Cherokee heater blower resister? I have replaced with new on and I only get low blow. It will go slow but high is slow. It has ATC. I think me wiring may not be correct. The new resistor has black, red wire. The GC has two greens and a small blue. Thanks
Submitted: 1 year ago.
Category: Jeep
Expert:  Juan Crespo replied 1 year ago.
Hi there. Welcome to our site. The ATC system does not have a resistor. Blower speed is controlled by by the Blower Motor Controller based on commands from the Automatic Zone Control Module.First thing we need to do is perform an ATC system diagnostic test to see what kind of fault codes are in its memory: ENTERING SELF-DIAGNOSTICS1. Turn ignition switch to ON position. Simultaneously depress and hold A/C and recirculated air buttons on the control panel. Rotate left temperature control knob clockwise one click. Continue to depress A/C and recirculated air buttons. All A/C-heater control panel segments should come on as a segment test. If any segment fails to display, the A/C-heater control panel is faulty and must be replaced.2. When segment test is complete, clear display momentarily by releasing the A/C and recirculated air buttons. If display remains blank, no faults are in system. If faults exist, active and stored faults codes will be displayed in numerical sequence. After all fault codes are displayed, the system will repeat fault code numbers. To stop this process, turn left temperature control knob one click in clockwise direction or turn ignition off. See RETRIEVING FAULT CODES. To return to test selection mode at any time during diagnostics, turn left temperature control knob one click in either direction. RETRIEVING FAULT CODES1. Depress A/C and recirculated air buttons at the same time and turn left temperature control knob clockwise one click. Release both buttons. A "00" display value will remain if there are no fault codes.2. If fault codes are present, each one will be displayed in numerical order (not in order occurred) for one second. The left side set temperature display will be blank. The right side temperature display will show active codes and up to 8 active stored codes.3. After all fault codes have been displayed, system will repeat fault codes. Record all fault codes. To stop this process, turn left temperature control knob one click in either direction, depress both the A/C and recirculated air buttons at the same time, or turn the ignition switch to OFF position. Please let me know what you find so we can continue.
Customer: replied 1 year ago.
I get fault codes 56 and 52. Thanks
Expert:  Juan Crespo replied 1 year ago.
Codes 52 and 56 pertain to left and right temperature door range being too large. These codes, added to the fact that the blower is not working properly even after replacing the controller (what you call the resistor), point to a bad Automatic Zone Control module (click here to see AZC module being sold on ebay for $79).AZC module Removal & Installation (2000 Models) Disconnect negative battery cable. Remove right switch pod bezel. Remove Automatic Zone Control (AZC) module mounting screws. Pull AZC module from dashboard far enough to unplug electrical connectors. To install, reverse removal procedure. Best Regards.
Customer: replied 1 year ago.
I put the AZC module in and it seems better, but I still don't get sufficient "blow" from the vents.
Expert:  Juan Crespo replied 1 year ago.
There are two possible causes of low air speed: one, the blower motor is not getting enough current; two, the blower motor can no longer turn at the requested speed.With the ignition OFF, disconnect the blower motor. Set your voltmeter to 20V DC, working from the harness-side of the connector, place the negative probe on the Black wire and the positive probe on the Red wire. Start the engine and turn the A/C on. Turn the fan control to HI. If voltmeter doesn't read full system voltage, either the blower controller (resistor) is not allowing full current to go through it or the fan control head is not sending the correct signal. If voltmeter reads full system voltage, then the blower motor has excessive internal resistance and can no longer turn at the requested speed.NOTE: System voltage refers to the reading you get when placing a voltmeter across the battery terminals with the engine running. Best Regards.
Customer: replied 1 year ago.
I get full system voltage (12V). Must be heater motor? Is it a simple remove and replace? We are talking about a GC Limited with dual control HVAC. Thanks for your responses. John
Expert:  Juan Crespo replied 1 year ago.
Yes, John. You should be able to access the 3 screws holding the blower motor to the housing from under the passenger side of the dash. Regarding price, it sells for under $100 at most auto parts retailers - cheaper online. Best Regards
Expert:  Juan Crespo replied 1 year ago.
Hi again. Just checking to see if the information I provided helped you solve your issue. If it did, kindly accept and rate my answer now. If it didn't, please reply.Best Regards.