no front heat JDM FZJ, rear heat OK (1 Viewer)

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Aug 5, 2022
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Colorado
hi

I've noticed recently I have no heat or defrost on the front system. the rear heat seems to work OK. It blows air just fine, but it's cold.
I have a 93 JDM which has the climate control setup like the LX450, kind of sort of automatic.

the heater control valve LOOKS ok externally, and the cable is being actuated with the temp slider. I feel warm water on both sides of the valve by feeling the inlet and outlet hoses. I'm somewhat confident the valve is functioning but thought I'd look around for other sources before I throw parts at it.

Not sure where else to look as I don't really know how the system works. Maybe the blend door isn't being actuated by the climate control? Anything else I should check?
 
The slider isn't mechanically connected to the valve on the auto climate control. The cable goes to a servo. Better off to check the valve position when going from hot to cold or manually moving the valve.
But it sounds like your heater core is restricted and needs to be back flushed. Does the air get warmer with the fan on the lowest setting?
 
The slider isn't mechanically connected to the valve on the auto climate control. The cable goes to a servo. Better off to check the valve position when going from hot to cold or manually moving the valve.
But it sounds like your heater core is restricted and needs to be back flushed. Does the air get warmer with the fan on the lowest setting?
Not really better on low, but one thing I noticed is if I leave the heat off then kick the fan on it’s warm for a little bit then cools off. You might be right about a restriction either at the valve or the heater core. I’ll pop the cable off and manually move the valve and see if it matters
 
The valve is better known to just fall apart when it fails, whereas these are classic heater core symptoms, especially if you haven't used it in a while or kept up on coolant changes
 
The valve is better known to just fall apart when it fails, whereas these are classic heater core symptoms, especially if you haven't used it in a while or kept up on coolant changes
I haven’t had it long but the coolant was not great when it came out. I’ll flush it and go from there. Cheap fix anyway
 
I haven’t had it long but the coolant was not great when it came out. I’ll flush it and go from there. Cheap fix anyway
yes that's a good baseline item. be sure to do a back flush on the heater core to get out whatever sediment/corrosion is blocking it up.
 
Flushed the cores and cleaned with clr. Came out like mud. It came out very slow and thick and after a few bucket fulls seemed ok. The clr had it running pretty much clear. I’m certain the core was so badly plugged all the water was just diverting to the rear core.

Still no heat. All the core hoses are hot so I THINK it’s flowing through the core ok now. The rear heat is working better after the flush

Is there a way to check the blend door without pulling the dash? Looks like some have gone down through the cowl with success but the details were limited. Or am I barking up the wrong tree by jumping to that?
 
Last edited:
Small update. I changed it from defrost to the upper vents and I’m getting a little heat. So maybe the core is still just a little gummed up. I’ll flush it more in the spring, for now I think I can live with it until it warms up
 

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