mmorris

01 Sport, new to us this summer. First time I 've tried the heater today with outside temp at 52 degrees and the temp gauge in dash reads just below 210. The heater doesn't seem to be heating like it should. Readings: inside air on full heat; 132 coming out of vent. 180 at radiator hose by thermostat housing, 130 at hose at top of radiator, 170 on top hose going into the firewall, 146 on bottom hose returning from firewall.
Check engine light comes on after about 10 minutes at idle.

Can someone tell me if this is normal and if not, what to check for and how to check it?
Thanks all.

Turbo X_J

It's blowing out 132° air (80° over ambient) and that's not warm enough for you?

RTorrez1

132deg at the vent sounds pretty hot to me. I know I wouldn't want to be in a vehicle that is 132drg.
If you want more heat??? You can start by giving the heater core a good back flush.

CCKen

Heater sounds normal, but what's the CEL DTC code? Have you had it read using a code reader?

mmorris

No, it just happened this afternoon. Can you take a battery cable off to reset the check engine light? Since it was idling for 10 minutes before the light came on, and had been driven on the highway for 20 minutes before that, I'm guessing that it might be an emission problem?

NewKindOfClown

You can pull the battery to reset it, but it'll come back if you have a problem. Any parts store should give you a free CEL diagnostic.

It's an '01? I've got $10 on a P0455 Gross Evap Leak engine code.

mmorris

Sorry, What's CEL?

NewKindOfClown

Check Engine Light. Sorry, I get complacent with all the acronyms cause I've been here too long

mmorris

Thanks to all. I'll flush the cooling system and see if that helps. I'm getting the CEL (now that i know what it is checked today.

mmorris

After flushing and cleaning the cooling system and changing the thermostat, the heater is still just blowing lukewarm air (about 95 degrees when it's 20 degrees outside). Which is MUCH cooler than our other vehicles' outputs. Is there something else I can try, or a test to see if the heater core is functioning?
Would it help to block off some of the radiator here in the Missouri winters?

CCKen

You may have a Blend-Air Door problem.

The Blend-Air Door mixes cool air from the AC Evaporator side of the HVAC Unit with hot air from the Heater Core side of the HVAC Unit. If the Blend-Air Door is not fully closing off the AC Evaporator side you will be getting unheated (outside air) air mixing with the hot air (the AC does not have to be turned on).

To check to see if the Blend-Air Door actuator is turning the Blend-Air Door fully from open to close (as it should), position yourself in the passenger footwell so you can look up to the left hand corner/bottom of the HVAC Unit, past the passenger floor air outlet. There you will see the Blend-Air Door actuator assembly (see pic in schematic below).

To check its operation, turn the ignition key to RUN(ON) without starting the engine. While looking at the bottom of the actuator, turn the temp selector (Red/Blue bands) from full hot to full cold. You should see the extrension shaft on the bottom of the actuator slowly turn 90 degrees from stop to stop. If it does this, the Blend-Air Door is doing its job.

If it doesn't turn you need to remove the actuator/motor and check its operation when not connected to the door.

To remove and check,

(1) Disconnect the wire connector from the blend-air door motor.
(2) Remove the screws that secure the blend-air door actuator assembly to the housing.
(3) Remove the blend-air door actuator assembly.
(4) reconnect the wire connctor to the motor.
(5) Do the operational check like you did above.

If the motor doesn't react, the motor is probably burned out. The power fuse for the motor is the same one for the HVAC Blower, so if the blower works the fuse is okay.

If the motor turns okay, the Blend-Air Door may be jambed. To check, try turning the door shaft with your fingers. If it feels like its binding, use a pair of pliers and see if you can turn the shaft back and forth to see if it will free up. If it doesn't the door is binding and can only be repaired by removing the HVAC Unit from the vehile and disassembling it to access the door.

If the shaft turns freely from stop to stop and the motor works properly your problem lies elsewhere.

Parts for the actuator/motor:

ACTUATOR, Blend Door - part number 5013741AA (Blend-Air Door Motor)

ADAPTER, Blend Door, A/C and Heater – part number 5013742AA (Motor Intermediate Drive Shaft)

BRACKET, Blend Door Adapter, A/C and Heater – part number 5013745AA (Motor to Housing Mounting Bracket)

When reinstalling the motor/actuator assembly, do this:

The Blend-Air Door only turns 90 degrees full travel. Viewing the bottom of the actuator, Full Clockwise is COLD (Blue), Full Counter Clockwise is HOT (Red).

When you are going to install an actuator assembly, plug it in to the connector first before attaching it to the Blend-Air Door shaft. Operate the actuator full travel hot then cold, Stopping at Cold (blue), turn the Blend-Air Door shaft fully Clockwise, then install the actuator assembly. Ops check it for full travel Hot and Cold. You should see the Intermediate Drive Shaft turn in the in the appropriate directions.

Install and tighten the screws that secure the blend-air door motor to the housing. Tighten the mounting screws to 10 in. lbs.

mmorris

The blend air actuator motor shaft is turning 90 degrees when changing from cold to hot. I'm getting COLD AC but lukewarm heat. Does this mean that the above shaft is probably moving the door correctly? If not, suggestions on how to get the actuator motor off? I can only see one accessible mounting screw and the diagram shows 3.

CCKen

If the shaft is turnng 90 degrees from stop-to-stop smoothly and without hesitation, the blend-air door and its actuator seems to be doing their job. No need to remove the actuator/motor.

If you are worried about getting only 95* F out of the vents with 20* OAT, I wouldn't be worried. I haven't measured the temp at my outlets but I am confident that its probably near 95*.

I don't think anyone on this forum can help you get your output air temp high enough to melt lead so maybe you should just live with it.

mmorris

Thanks to all that offered advice. I will just live with the lukewarm air; this week should be a test as it's supposed to be in the single digits in MO.

CCKen

You may be better off leaving the Blend-Air Door in full hot position for now. If you removed the actuator and moved the door shaft by hand you may find that the door is binding and not going to the full hot position stop, and there's little you can do about that without removing the HVAC Unit and repairing/replacing the door. Although there is an outfit on the internet that sells replacement doors, etc., but it involves cutting away part of the HVAC Unit to replace the door. I don't think you want to go there right now.

Here's a temporary measure you can take that may help you through the winter:

Unplug the Low Pressure Cycling Switch connector (on top of the AC Accumulator). Wrap the connector(s) ends with electrician's tape and secure the wire harness.

This will deactivate the AC system entirely and will allow you to use the AC selections on the Mode selector, which includes the MAX Air/Recirculation setting. This will open the Recirc Air door and allow recirculation of cabin air only and blocks off the cold outside air from entering the HVAC Unit. In this position you will have air flowing out of the panel outlets on the instrument panel. Continue using this setting untill the cabin heats up, then you can switch to the AC Bi-Level setting which will flow air out of the instrument panel outlets, the floor outlets, and the outlets on the rear of the center console.

Of course, all other selections on the Mode Selector are still active. The only issue you may have is that you won't have the AC Compressor on line providng AC to assist in removing moisture from the air in the MIX or Defrost settings, and demisting (defogging) the windshield and side windows will take longer. But then again, the AC compressor will only engage if the outside air temp is above 30*F, so this may be a non-issue in single digit outside air temps.

Although not mentioned in the (my) Cherokee Owner's Manual (that I can find), it may be a good practice to reactivate the AC system every two months and run it for about five minutes to insure adequate system lubrication to minimize the possibility of compressor damage when the system is started up again next spring.

Good luck.