Ac/Heat doesn't work when I turn it on....

Could be a number of thing's ! Testing the electrical circuit is the way to find out what's wrong . Using a wiring diagram and a DVOM - digital volt ohm meter . Videos on youtube showing how to test it ! Without testing i would only be guessing . Does it work in high speed ? In high speed it by-passes the resistor . If it doesn't work in any speed more then likely the blower motor is the problem !
Air Speed
The HVAC control assembly applies ground to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:
• Low speed--3 resistors
• Medium 1 speed--2 resistors
• Medium 2 speed--1 resistor
When the operator requests High speed, the HVAC control assembly applies ground directly to the blower motor through the high blower motor control circuit. The resistor card has a fusible link which, if blown, will require that the card be replaced.

Blower Motor and Resistor Diagnostics by Wells

check fuse first
then scan PCM , oops you didnt and the BCM does run this stuff.
so not scanning it , you miss all those FACTS.

the blower is dead. (aka , not spinning , or silent)
on all cars made the answer is the same.
blown fuse, fuse marked BLower, is blown. LOL.
controls not turning it on, controls failure.
blower bad. (motor) hot wire it in place to test)
wires to any of the above.
or the resistor block bad, (if it works on high but not low)
i have the schmematic in hand.

the HVAC relay pulls in by command of the BCM
the relay then sends 12vdc power to the blower via fuse 41
the blower is now hot full time.
the blower then needs a ground to spin (run)
on high, the ground G601 via the speed knob,switch makes that ground connection, so if the fan dont spin and say the fan is ok
then the relay is not closing or the fuse 41 is blown. (why not look at the fuse first for all electric fails)
the BCM sees you, turn fan on, (heat or cold)
and closes this relay, on the left.
if the relay does not close, (and coil is ok inside)
the the BCM didnt see those HVAC requests.
use a scan tool and look for BCM errors..>??????

Pull two fuses, and compare them.
A "blown" fuse will not have any wire connecting the two ends, while the "good" fuse will visibly have a thin wire.

YJ car.
the blower is dead. is that it?
does it blow full speed on high
do you have 12v on terminal A of blower , term B is 0v ground
got that, then the blower is dead.
if not 12v, then the controls are bad.
http://www.jeep4x4center.com/knowledge-base/index.htm?utm_source=cj#service

page 47
4 parts to make blow
1: fuse 12 good.
2: switch heater /on off.
3: high, med,low speed, use high, its direct.
4: the blower,
one of those points has no 12v on high,
use a simple voltmeter to find the failed point.

check all your wireing

see this steps and fix it. God bless you

Start the car and turn the air conditioning on. Allow the engine to run a few minutes so the air can cool. Check to make sure you have the proper buttons selected. This simple step may uncover the root of the problem.

2 Adjust the air controls on the dashboard to see how they are working. If the controls move the way they should with the proper amount of resistance and stopping in the right places but have effect on the air, then the problem may as simple as a blown fuse. If the controls are not working at all, then the problem is in the control panel.

3 Get to the fuse box in a Ford Explorer by removing the instrument panel to the left and slightly below the steering wheel. There is a fuse remover provided in the fuse box. A blown fuse will have a broken wire in it. In a Ford Explorer, this fuse is red number 10.

4 Find the control panel by prying off the top instrument panel around the air conditioning temperature controls. Unscrew four screws, one in each corner, and remove the temperature control panel. Unplug four electrical connectors and one vacuum hose to the control panel.

5 Listen for the blower motor to be properly working while the engine is running and the air conditioning controls are turned to high. Adjust them from low to high to make sure the blower motor noise increases and decrease accordingly.

you have a bad blower motor resistor. They are nomally close to the blower motor on the passenger side under the dash. If you follow the wires from the blower motor it should lead you right to it.

Check fuse panel for blown fuse first.

it's either a fuse or it's a bad blower motor, it could be a bad blower motor resistor but usually you'll get either high or low only, so if you have nothing on any speed, high low etc, and all the fuses are ok chances are it's your blower motor.

You need a blower motor resistor,and the heater blower motor should be checked for high amp draw. check Napa for the part or go to Dodge..prpbably about 60.00 dollars.