landonshenk

When i turn my heat on it does not match the air flow like the air flow when cool is on also my heat sucks i need a anwser the blower motor sounds the same on both cool and hot so whats wrong

landonshenk

also its a 1987 jeep cherokkee

cruiser54

By chance is the bulk of the air going out the defrost?

landonshenk

No actually it’s not

Saudade

So when on HEAT, you do get heat but the air flow reduces as if you turned the fan to a lower setting?

When you switch from Vent to Heat to Defrost, does the airflow change to those ports?

With the HVAC on an AC mode, have the temp control to full cold, fan at full speed. Take note of the air flow. Now slide the temp control over to full hot. Do not change the mode, leave on AC. Does the airflow reduce?

landonshenk

the airflow does reduce a lot and the blower motor is working exactly the same

Saudade

Hmm. Airflow through the HVAC box always passes through the evaporator. The blend door either allows the air to also flow through the heater core (when you move the temp selector to warm (red) or bypass the core when you move the selector to cool (blue). Since you're getting full airflow with the selector on cool but less on warm, I suspect the core is blocked. Not blocked internally for the coolant, but blocking the airflow through it.

Here's the schematic. Note the position of the blend door (in red) when temp set to warm.




Here's a previous thread showing the guts inside the box. Note the position of the blend door in the pic.

https://www.cherokeeforum.com/f2/hea...9/#post3590210

landonshenk

so what do I need to do to fix it a new heater core ?

Saudade

Did you just buy this XJ or have you had it a while?

Did the heat ever work?

Could there be a mice nest or something else blocking the airflow?

Do all the vents work when you switch modes (floor, defrost dash)?

Yanking the HVAC box is a fairly big job. Lot's of YT vids on it. Hate to have you go through this and find out it's something else.

landonshenk

my grandad has had it since 2007 I would have to ask him but It idk when I changed the blower motor no mice nests were in there

landonshenk

is there anyway I could get a vacuum cleaner in there and clean it out

RockyMtn96XJ

Heat comes out of the floor vents. Just sayin'. I didnt see it mentioned so I figure I would speak up just in case.