Heater will not blow hot air
 

Ok so i've done my research to an extent and just wanna get an idea from you guys on what may be going on...My jeep warms up good, both heater hoses are hot, the heater control valve was deleted and ran straight into the heater core...so the problem is when it gets warm and i turn the heat on i only get barely warm air, not hot air as it should be...Oh and i just noticed today that there is a hole under the passenger side where the air blows and its missing the piece that screws into it and has a 4 wire electric connecter, anyone know what that piece is? and may that be why the air isn't hot?

You may want to start by flushing the heater core in both directions. Just because both hose to the core are getting hot it can still have crud built up and not letting the brass tubing to get hot enough to pass on the heat. If I am not mistaken the piece that is missing is just the cover that covers your heater resistor ( The piece that has the wires).

You'll have to post a picture for any type of meaningful response, are you referring to the blend door perhaps?

my 00 cherokee is doing the same thing. I did the headgasket and had the head machined about a year ago. Replaced the water pump, clutch fan, radiator, you name it. Never really had good heat before or after that. I backflushed and flushed the heater core no joke probably 20 times. I would blow it with water and than blow through the tube with air to blow the crap at the bottom out. Did both of these techniques till I could blow clean water in both directions through the heater core.

The heater core is not leaking nor is the rest of the cooling system. What other reasons could explain the lack of heat. Could the insides of the heater core be so clogged that it will blow water clean but the coils themselves are deteriorated/rusted/dirty?

Love to hear thoughts

If I'm understanding your discription correctly, the hole is for the ballast resistor.

Does the fan work at different speeds or just 1 speed only?

The blend door is what diverts air through either the evaporator coil or the heater core.

Have you looked for vacuum leaks or a disconnected/missing vacuum reservoir?

Yes the fan only works on high, and should have that part tomorrow...and im gonna try flushing the core tomorrow if i have time.

Alright so i went and did some messing around with it and i decided to look under the dash and seen the cable and arm that moves the flapper door from warm to cold, and sure enough it wasn't completly closing out the cold air...so as i suspected in the first post it was letting both cold and warm air in...i should've checked that before posting but i thought that cable was behind the dash and not easy to get to...but anyway that explains why it wasn't very warm...thanks a lot guys now its blowing much warmer.

resurrection!

exact same problem and have done the exact same things with my 01...its getting cold here in Canada and this is pi$$ing me off to the point where I'm about to sell my lovely xj for something that doesn't have me freezing

This?

is that broken or working? I assume thats on the passenger side?

It needs to be in proper adjustment. Passenger side.

Slight thread hijacking but a quick question: Is it possible to disconnect the heater core hoses without loosing any coolant? I flushed the system but forgot to flush the heater core and hate to replace the coolant again. I was thinking just to disconnect the hoses from the firewall side and run water from the garden hose through the core.
Sorry about the tangent...

You'll lose some coolant.. Not a good way around that really. But it can be done

So I flushed my whole coolant system again. Heater core alone and then the whole system backflushed the whole nine yards. The heat worked for a week and now isn't working again! The ac blows cold all year round but where I live it's cold for seven months out of the year and this is starting to get ridiculous. My vent door works fine. Should I change my heater core? If this doesn't work I'm selling this heep and buying something else.

Here's an easy test. See the hoses going into the heater core through the firewall? Are they both the same temperature with the engine warm? No need to go high-tech here. Your bare hand will work fine.