Where is the expansion valve located

The expansion valve regulates the amount of freon entering the rear evaporator. It is directly connected to the evaporator inlet tubing and has a temperature sense bulb attached to a fin of the evaporator.

If the front blows cold it would suggest that the freon level is ok. However, if the freon is low, it still may blow somewhat cold in the front and less adequate in the back. Have you had the pressures checked to verify the charge is ok? Does the rear fan motor work? There also may be a restriction or defective expansion valve in the rear causing little/no freon circulation. Another problem could be a defective/stuck blend door in the rear causing the cold air to not circulate

The expansion valve is bolted directly to the evaporator core. You will need to recover the Freon before attempting to remove this. Once the Freon has been recovered, and the expansion valve removed, be sure to cap off any and all a/c lines to prevent excess air/moisture from entering the system. Once the new valve is installed, you will need to pull a 30 hg vacuum on the system for at least 30 minutes then recharge with the proper amount of Freon.

HVAC?
topic HVAC?,not A/T?

the A/C expansion valve, is just next to the evaporator
in fact it does the evaporation, so must be there.
next you ask were is evap, right?
its in the FSM read it
or at alldata.com
see HVAC chapter, i promise its there, and TONS MORE.
why not post symptoms and leave guessing to TV experts.
post em.
btw the loop can have many issues. (even wrong freon or worse)

Right next to the blower motor box is the evaporator box,the expansion valve is connected to it,to remove and replace,you will need to remove freon,I just had my evaporator replaced with a new expansion valve on my 85 nissan truck,was going to do myself,but I am not set up to remove freon and do a leak test,so I took my truck to Midas,and it works great now.

Is the system full of freon ?
The rear ac uses an expansion valve, and the front ac uses an orifice tube. One system can work independently of the other.

Kia Sedona expansion FRONT valve located under dash, behind glove box, fan and coil. Evacuate freon first. Disconnect Freon lines from firewall., Lay right front seat back to flat horizontal position and lay on top or totally remove the seat for easier working access. Remove under dash cover, fan, glove box, coil housing, remove coil mounting bolts, remove old expansion valve. (Inspect old valve, if debris inside, blow out coil before installing new valve. If visible debris best to consider replacing REAR expansion valve and DRIER/FILTER in front of radiator too and blow out all lines and coils while servicing.) Use compressor oil to lubricate "O" rings on new FRONT or REAR expansion valve, install valve bolts, reinstall coil bolts to FRONT firewall or REAR frame, reconnect freon lines to firewall in engine compartment. Evacuate AC system, install freon (35 1/2 ounces, nominal 3 pounds), check system for leaks, check for proper operation, enjoy.

Grand Am has an expansion valve. Link below has part number and picture of what you are looking for.
http://www.discountacparts.com/addtocart~year~1998~make~Pontiac~model~Grand_AM~descript~A-C_Compressor~part~60-40281.asp

Unfortunately, I do not know precisely. But for the most part auto a/c's are all the same. Below I will describe how to find it. I have also included a aguide to determine system operability that may or may not be helpful. Just trace the system with flow path described below the valve has to be between condensor and evaporator.

Reminder the flow for the a/c system is :
1. From the compressor a high pressure (HP) gas goes to the condenser in front of the radiator.
2. From the condenser a HP liquid goes to an expansion device (orifice tube or expansion valve)
3. From expansion device the low pressure gas enters the firewall to the evaporator.
4. From evaporator the low pressure liquid/gas mixture goes through the dryer back to the compressor suction.

Below is a guide to troubleshoot and check system function. This can be done by most folks.

Look at the front of the ac compressor and have someone turn on the ac from inside the car. The front of the pulley(clutch) will spin when turned on.

If it does not spin, the low pressure switch (LPS) is not satisfied. Meaning there is not enough freon in the system to operate the system. Means low freon capicity because of a leak.

The LPS can be jumpered to cause the compressor to run (clutch to engaged) which will draw the freon in the system.

The LPS is usually a two wire sensor on the suction of the compressor. (between evaporator and compressor) Unplug the sensor and install a jumper, this will engage the clutch. Connect a new can of freon
and fill to system capacity.

The capacity of the ac system will be on a label under the hood, do not overfill. Probably about 2 lbs. Local parts stores (Auto Zone and Advance) will have freon with stop leak. This may help the leak. They also make a freon with a UV dye. I always add a single can with dye so that if stop leak does not work I can find the leak in the future.

The system should be filled until suction pressure is about 30 to 38 psi..

The rear expansion valve is connected to the evaperator. I hope this helps.
Thank You,
Roy

Expansion valve is located passenger dash area , inside the evaporator housing. This is not a repair that can be easily done by a home "do it yourselfer".It requires evacuating the the air condition system of freon is the biggest obsticle doing at home. Rec. taking to a certified a/c repair shop for this repair.