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not the usual heater problem ....

anthony

NAXJA Forum User
Location
toronto canada
91 mj 4l 2wd auto

problem: no heat

so right away i swap out the thermostat for a new one, top up the coolant, bleed the system and take the truck for a run to road test .. still poor heat .. i resign myself to a heater core swap in my FRIGID barn and go to check the tranny fluid level on an unrelated issue .. i get out of the truck, the hood is still down and through my wooly winter hat i can hear a rush of air from the cowl area .. i pop the wiper arms and yank the cowl cover and there's a monster air draw through the cowl vent that goes inside the cab on the passenger side .. clearly the vent door is stuck open and diluting the hot air from the heater core

ok .. so i get under the dash and with a flashlight in one hand and the other working the heater controls i try to find the vent door control to no avail

guys it is insanely cold up here in central ontario .. can anyone offer me any advice or point me in the right direction to get this vent issue resolved and save me from a frosty death ?? please and thanks

edit .. all my searching just keeps turning up snorkle writeups :)
 
how about just blocking off the cowl area or would that leave the blend door closed to the heat?

i have a cable on my 89 that runs under the passenger side dash to the blend door.

does that year have a heater control valve? maybe its bad.

are both lines to the heater core getting hot? could be a clogged heater core
 
there's tons of heat in the engine .. the top hose is nearly untouchable and both sides of the heater hose are toasty .. it does have a heater control valve; does that have any bearing on the cowl vent door ???

the cable on the passenger side right by the tranny tunnel works perfectly .. i go from hot to cold on the dash control and it moves flawlessly .. there's gotta be a door somewhere above the blower fan and heater core that blocks off the outside air vent that is related to the hot/cold, it only makes sense .. it's just way too cold for exploratory surgery

thanks for replying 89xj; appreciate it mate
 
I am no expert on this issue, However, you can see your heater control valve on the engine side connected to your heater hoses just near the firewall. It diverts hot water into the heater matrix as you turn up the heat. You should be able to see it move if you get someone to turn it to full heat.
I would suggest that if both your hoses are hot then your your heater valve should be working??? but like i say, im no expert, im sure someone will come along soon and confirm.
Have you had a look on ebay regarding "jeep blend door fix, heater fix, heater treater, something like that. There you will see roughly were the blend doors are situated behind your dash. If you want to do it properly i understand you may have some work on your hands as the dash needs to come out.
 
mike reid 350, it appears that hes in Ontario.

He had a problem that you got. Maybe he could tell you more
 
AFAIK, the door is only closed on RECIRC or MAX (typcially AC functions). So, check the blend door as others have suggested. It's cable operated and sometimes the end of the cable comes off. You should feel some resistance and maybe even hear the clunk of the door reaching each limit.
 
i should have mentioned it's an AC delete vehicle .. sorry

i'm gonna try pulling out the glove box and see if that gives me any kind of access

thanks for replying saudade
 
I had about the same problem, no heat at idle, heat over 2000RPMs. I just took out the heater valve and it works now. Might wanna try that before you go taking your whole dash apart.
 
cheers imboostedru

the heater valve in the heater hoses works perfectly .. i looked at that already .. one heater core inlet is crazy hot, the other one is less hot so the heater core is functioning correctly

according to my FSM there's supposed to be a recirculation door that controls how much air is drawn through the heater core from outside the vehicle as opposed to how much air comes from inside the cab .. clearly at full heat the door would be completely closed and it isn't, because cold air is being drawn through the cowl .. i can feel it, and see it pull the flame of a lighter

however the FSM diagram is highly ambiguous and i can't figure out the exact location of the recirculation door from that .. it would make sense that's it's gonna be close to the cowl on the passenger side .. i pulled the facia off the dash and found the glove box is pop riveted in and i kinda stalled there and fixed some other unrelated issues instead (tranny cooler lines etc)

someone must know where this thing is ???
 
AC delete vehicle have no recirc. door. I think it blocked off somehow. All of your heater air must come in thru the vent. Nothing's wrong there. Don't ever block off the air intake at the cowl. I always clean off the snow and ice here before I run the heater. (Blower motor and resistor can burn up if airflow is restricted. It's either your heater core doesn't have enough hot water flow (inline water valve, or core blockage), or your blend door isn't getting to the right position.
 
that explains why i can't find it .. thankyou sir

i'll try flushing the heater core with a calcium/lime/rust formula

appreciate all the input guys, cheers
 
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