Replacing the heater core on a '88 Plymouth Sundance?

under the dash on the passenger's side

spend 20 dollars and get yourself a repair manual on ebay before you take a wrench to it. it is pre 90s passenger airbag so you should be able to do it yourself with enough time. do a search on youtube, lots of car videos there.

check the temp of the heater hose going into fire wall,make sure they are both the same temp,if they are replace the thermostat.
if one is hot and the other is not,the heater core is partially block and will need blowed out with air hose or replaced

Quite often you'll find resistor on firewall, of passenger side under hood. 1-1/2"x3" block attached to firewall. In area of where heater hoses enter.

I don't have a manual for the 1988 Plymouth Sundance, but I'll see what I can find.  You would replace it.  If you/your daughter plan to keep the car for a whle (and you plan to be her mechanic), I would recommend purchasing a Haynes manual for it.  As soon as my vehicles' warrantees expire, I buy the manuals. The MAP (Manifold Absolute Pressure) sensor is usually connect to the air duct near the intake manifold.  Looks like for your car they run from $40-$70, depending on your engine size and turbo or not.  Good luck!

first.... open the hood... yes the hood.... look on the firewall... you will see two rubber hoses going into it... that is where the heater core is located... generally it's on the passenger side but sometimes ..... in my dad's van for one it's mounted in the center... dodge's better idea i guess. while you are under the hood .. examine the hose connectors.... if they are hose clamps easy... if they are special connectors you will have to visit autozone or canadian tire or auto parts store to borrow the tool.... usually have to leave a deposit....
now... climb under the dash on the passenger side and look up... if there are sheilds to remove them... you will need to do that... i often remove the glove box to give me even better access and to see better what i'm doing.
the duct work is often held together by screws or clips. make sure you remove all the ones necessary ... front and back... it's usually a split shell so you only need to lower the one half......... pull the duct work carefull away from the heater core ... look for bolts hold it on ... usually again on the outside by the firewall... before take the bolts out use the tool to remove the hoses. you did drain some antifreeze first right ? .... it's tough to get all the water out so before you pull old core out either be fast about it so you don't spill antifreeze into the car... or tilt it up to drain some fluid out on the outside first.

remove the old core... install the new one... bolt it on... reinstall the duct work.... clean up... reinstall the hoses... refill the rad and leave the cap off when you start it up to add more fluid....

almost done... pinch the hoses gently when the motor is warm to move the air out of the system.... after you install the rad cap... take it for a drive.... when you get back wait till the rad is cool again and take off the cap... fill the rad up again... repeat that a few times to compensate for air bleeding out of the new core...

Robert

P.S. i did a heater core on a 69 dart i used to own.... basic car no options... took me fifteen minutes lol

I have located a chilton manual CD online that I am will have in two days. Just hope it doesn't rain between now and then.

The heater core is up in, and under the dash. To remove it is a rather extensive job. I'd recomend a shop manuaul. The center consol, radio, heater control, glove box, and possibly part of the steering column will need to be removed first. The hoses on the fire wall in the engine compartment will need to be disconnected. If the unit also has A/C, there are a few other items to be considered.

first check bulbs and fuses if no success the reverse light switch is located on gearbox sometimes wires come off and other times faulty and need replacing a test lamp on the switch will help to tell you whether or not power is coming out when in reverse to make the lights work

i have a manual with step by step instructions,no diagram but helpful.
if you still need it i can scan it and email it to you