Where is the front fan resistor unit?

Don't worry about. Open the glove box and release it the fold down. Tabs on the side or top. The resistor is right there, replace it. don't buy a junk one, You'll be doing this every year.

There are several reasons for a blower to stop working. Does it work on ANY speed? Does the AC compressor lamp or any of the vent control LEDs still work when using the AC controls? Do ANY of the speed for the blower work or are they all dead?

1st, you wanna check your fuses. There will be fuses in the underhood fusebox marked blower or heater fan, check and repalce as necessary. Also, if the earlier check for working LED bulbs on the AC control panel showed some or all lights dont ever turn on when engine is running, you may have problems with the control system.
if the fuses are good, now you need to test parts. there is a blower motor speed control aka blower resistor that frequently fails on most cars. It is the part that carries the current for all speeds of the blower and regulates speed when commanded. It has to absorb the excess energy to lower speeds and it tends to get very hot and burn out as a result. If it has failed, there will be power IN on one of its wires, and no power OUT on any others. If you have no multimeter or testlight to check things like this, Id recommend taking it to a certified mechanic.
If the control lamps all work that means controls have power, if the blower resistor has no power, fuses or blower relay are the most likely cause. if the blower resistor has power but still no fan, most likely your fan has failed. as a general rule, I replace fans and blower resistors as pairs. fans tend to last longer, but they also get more demanding with age (kinda like people) and that extra demand will burn out the newer resistor much faster than when the fan was newer. it can be alot of time and money to change a blower TWICE, so to be sure it wont fail again, test current, or simply replace the blower fan if it is determined a resistor has failed. (a good fan in theory shouldnt draw enough amperage to burn out a good resistor, EVER, so if the resistor burns, the fan is typically drawing too much power, and even though it works "fine", it will burn the next resistor in a short time as well.).

This is common you will need to check the front blower resistor, this is located under the dash on the passenger side on heater box next to blower motor. the wiring plug also needs to be looked at. the plug on some of these heats up and starts to burn and in turn the connector needs replacing and the resistor also.
If the connector is good then replace the resistor and that will solve the blower problem.As far as the rear unit not blowing hot air , make sure the coolant is full and if the coolant if full then you will need to take a look at the rear unit blend door. this is the door that opens and closes to control hot or cold air, if the coolant if full in radiator then blend motor may be bad, testing will need to be done to see if its the door or the motor that controls the door. good day

Should be in fuse box under hood have you tried running hot wire off the battery straight to the fan to make sure motors good.

The most common problem would be a bad blower at which you can test for power at the motor connector with a testlight, the other most common problem is the resisitor ,theres one for the front blower and one for the rear blower, you may have a bad resisitor for the rear blower this resistor is located next to blower.theres also arelay in the fuse/relay box next to the battery under the hood,the best thing is to start testing for ower at the switch and work your way to resistor, i think you will find a bad resistor to rear blower motor.heres a complete wiring diagram of the whole front and rear heat and ac unit, everything is labeled good luck.

check the resistor i think it's a 7 way connector located by the blower motor i have had were the connector has melted to the resistor if this is the case you will need to replace both resistor and connector
the connector is available at a GM dealer or a AC DELCO parts dealer not sure about aftermarket
hope this helps

some quick testing would help. test for voltage at the resistor. if there is voltage at the resistor, check for voltage at the fan. if you have power at the fan, remove the fan and hook it up to 12 volts to see if it spins. watch your fingers in case it does spin as it usually spins very fast.
i've seen brand new parts right out of the box that were defective so you need to rule out the resistor and the fan first. if no power is present and the fan works, test the power going to the switch that controls the fan speed.
incidentally if you are visually checking the fuse, pull it out and use a meter to check if there is indeed continuity.

robert

is there 12 volts to switch to resister to fan? if so reground your fan

I had the same issue on my 1999 Grand Cherokee. I replaced the fan motor which was only 68.00 from Auto Zone and the fan relay sensor which is located behind the front left side of the bumper, which was about 30.00 from Autozone. I would suggest testing the motor with the 12V (fused). You can test it with your car battery, if it works, then i would suggest replacing your fan motor sensor, behind the front left side of the bumper.

I had the same problem. Check the fans relay behind the front grill, in front of the radiator, more accesible if you take the headlight (driver's side) out.