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Strange heater problem

1990XJ4x4

NAXJA Member #1158
Location
Louisville, KY
This is driving me crazy, my heater works, but not well enough to heat the jeep up. The air doesnt blow out of the vents very strongly and the air is lukewarm. The doors inside appear to be working because the heat/vent/bi-level/defrost switch does its job. This is the second winter i have been battling this.

A little background on what I have done:

90 XJ, no A/C converted to an open cooling system using a new radiator and heater control valve from a 93.

Replaced the heater core last winter
Replaced the blower motor a month ago
Did cooling system swap this last summer
t-stat this last summer

One problem I know i have is not getting vacuum to the heater control valve, but even after sticking it in the heat position it is all still lukewarm.

My temp gauge will generally run anywhere from 170-200 (20 degree weather) without ever kicking on the electric fan (on a switch).

Any Ideas? :dunno:
 
try bypassin the heater control valve maybe? Sounds like there is a blockage somewhere. On my 88 I took the control valve out because it always leaked.
 
I'm not sure I have a lot of insight into why you're having the problem, but I'm facing the same problem. One thing to check to perhaps help narrow the problem is to feel the hoses going into and out of the controller. Even though mine seems to open and close properly when selecting heat or cool, the input hose feels very hot but the output side only feels lukewarm. I'm assuming I'm having an issue with the controller itself of some sort of flow problem (either through the heater core or elsewhere past it).
 
found my problem today. After checking fuses,relays, vacuum lines i dicovered that it was a bad connection of the wiring harness that plugs into the back of the heater /ac controls. One of the wires(purple/yellow stripe) comes straight from the fuse box. I cleaned the connections and everything works again.
 
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