Vacuum problem?

Every so often my AC doesn't want to blow cold air but it blows hot air. So moving the turn knob couple of times gets it going (I ussually turn both the ventilation type knob as well as the temp knob). So I'm wondering, should I look into doing the vacuum lines? It's a 98XJ and the vacuum lines have never been touched...... Any tests that I can run? I don't have cruise control so that test is out of a question.....

Kejtar

Sounds like a sticky heater control valve.

ok.... what do I do about that sucker, how do I test it.. and where is he at?

I would disagree on this. I would check the door that pull air thru the core or around it. Possable it is jammed? If it is operated by vacuum I would look to the solinoid that controls it to make sure it moves when the controll is moved. in this case the FSM is your friend.


Rev

OK, but a heater control valve that isn't closing will cause the A\C to blow hot air.

Kejtar, they are only $13 new and if it doesn't fix the problem, take it back. It's located under the hood, passenger side back near the firewall.

ok... I will have to find some time to dig into it Grrr it seems like every time I turn to do something, something else falls appart either on the jeep, or something has to be done in the house...... ok... the following weekend... maybe

Kejtar

SactoXJ said:

OK, but a heater control valve that isn't closing will cause the A\C to blow hot air.

Kejtar, they are only $13 new and if it doesn't fix the problem, take it back. It's located under the hood, passenger side back near the firewall.

Click to expand...

What else could it be called? I looked in the fsm and I couldn't come up with what you're refering to

Kejtar

Remi. its the little valve that is on the input to the heater core, open to allow coolent into the core when you call for heat. I still think its the mixer door. You did check for vacuum on the HVAC system.....right?? Can you switch the location the air comes out of??

Rev

I'll be looking into that tonight and tomorrow....

Remi, I think it's listed under water valve.

OK... this is the table of contents and I can't seem to find a water valve either. Possibly should I be looking at heater/ac housing door as that's responsible for blending air and heating...

Kejtar



ACCUMULATOR
BLOWER MOTOR
BLOWER MOTOR RELAY
BLOWER MOTOR RESISTOR
BLOWER MOTOR SWITCH
COMPRESSOR
COMPRESSOR CLUTCH
COMPRESSOR CLUTCH RELAY
CONDENSER
DUAL FUNCTION HIGH PRESSURE SWITCH
EVAPORATOR COIL
FIXED ORIFICE TUBE
HEATER AND AIR CONDITIONER
HEATER AND AIR CONDITIONER CONTROL
HEATER CORE
HIGH PRESSURE CUT-OFF SWITCH
HIGH PRESSURE RELIEF VALVE
LOW PRESSURE CYCLING CLUTCH SWITCH
REFRIGERANT
REFRIGERANT LINES
REFRIGERANT LINE COUPLERS
REFRIGERANT OIL
REFRIGERANT SYSTEM SERVICE PORT
VACUUM CHECK VALVE
VACUUM RESERVOIR
DIAGNOSIS AND TESTING
A/C PERFORMANCE
BLOWER MOTOR
BLOWER MOTOR RELAY
BLOWER MOTOR RESISTOR
BLOWER MOTOR SWITCH
COMPRESSOR
COMPRESSOR CLUTCH COIL
COMPRESSOR CLUTCH RELAY
DUAL FUNCTION HIGH PRESSURE
SWITCH/HIGH PRESSURE CUT-OFF
SWITCH
HEATER PERFORMANCE
LOW PRESSURE CYCLING CLUTCH SWITCH
REFRIGERANT SYSTEM LEAKS
VACUUM SYSTEM
SERVICE PROCEDURES
REFRIGERANT OIL LEVEL
REFRIGERANT RECOVERY
REFRIGERANT SYSTEM EVACUATE
REFRIGERANT SYSTEM CHARGE
REFRIGERANT SYSTEM SERVICE
EQUIPMENT
REMOVAL AND INSTALLATION
SERVICE WARNINGS AND PRECAUTIONS
ACCUMULATOR
BLEND-AIR DOOR MOTOR
BLOWER MOTOR
BLOWER MOTOR RELAY
BLOWER MOTOR RESISTOR
COMPRESSOR
COMPRESSOR CLUTCH
COMPRESSOR CLUTCH RELAY
CONDENSER
DUAL FUNCTION HIGH PRESSURE
SWITCH/HIGH PRESSURE CUT-OFF
SWITCH
DUCTS AND OUTLETS
EVAPORATOR COIL
FIXED ORIFICE TUBE
HEATER-A/C CONTROL
HEATER-A/C HOUSING
HEATER-A/C HOUSING DOOR
HEATER CORE
LIQUID LINE
LOW PRESSURE CYCLING CLUTCH SWITCH
KICK COVER
MODE DOOR VACUUM ACTUATOR
REFRIGERANT LINE COUPLER
SUCTION AND DISCHARGE LINE
VACUUM CHECK VALVE
VACUUM RESERVOIR
SPECIFICATIONS
A/C APPLICATION TABLE
XJ HEATING AND AIR CONDITIONING

Sorry Remi, that's the only way I could find it listed on an A/C vacuum control schematic that I have. No part numbers listed for it either.

hmm ok... I'll look again at the schematics when I get home

My money is here...
HEATER-A/C HOUSING DOOR

but, the valve is prbly listed under Cooling system.

Rev