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Ask Juan Crespo Your Own Question
Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Jeep
Satisfied Customers: 1523
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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Grand Cherokee: I have a 96 grand cherokee. The blower motor

Customer Question

I have a 96 grand cherokee. The blower motor will not run under normal conditions. it has power all the time(with or without keys on) but no ground. I have replaced the blower motor and the resistor. the only relay I found is in a fuse block at the passengers feet. The relay i was sold at the parts store has a tab on it for mounting with a screw. if i compare te 2 relays they seem to match except for the outside housing. when I tried the 'new' fuse in the fuse block that was no difference. any ideas?
Submitted: 1 year ago.
Category: Jeep
Expert:  Juan Crespo replied 1 year ago.
Hi there. Welcome to our site. The blower motor is powered all the time, but its controls are on the ground side of the circuit. In other words, we should be looking at the switches and/or resistors to be the likely culprits.Which type of A/C controls are there in your GC, automatic or manual? Do you have a good voltmeter you can use? Can you read a wiring diagram?
Customer: replied 1 year ago.
Customer: replied 1 year ago.
I have meters, yes I can read wiring diagrams
Expert:  Juan Crespo replied 1 year ago.
Great. Give me a couple of minutes to upload the diagram and we'll work on it. Be right back!
Expert:  Juan Crespo replied 1 year ago.
First thing we need to do is remove the control head but leave it connected, then check for ground at terminal C4 Dk Green wire (see attached diagram). If OK, turn the ignition ON and turn the A/C to any mode. Turn the blower to High. Check for voltage at terminal 3 Black/Tan wire. Is there system voltage (>10 volts)?
Expert:  Juan Crespo replied 1 year ago.
Going off-line for today. Will be back tomorrow after 2PM ET.
Best Regards.
Customer: replied 1 year ago.
I have continuity from chassis ground to dark green with the key off. I have 1.5vdc with the fan on high
Expert:  Juan Crespo replied 1 year ago.
Good, now we know there is a good ground path. When you say "I have 1.5 V with the fan on high" does that mean there is 1.5 volts at terminal 3 Black/Tan wire? If so, there might be a voltage drop somewhere in the ground circuit. Tell me, is the blower motor running at full speed during the voltage test? Can you unplug the blower resistor and repeat the test, this time with the engine running?
Customer: replied 1 year ago.
I have 1.5 volts on the black/tan wire with the engine running. The blower motor does not run at all. I will try unplugging the resistor and checking the voltage again with the engine running
Expert:  Juan Crespo replied 1 year ago.
Please let me know when you do.