Mountain Mule

My heater is not blowing hot air, just warm. I live in Colorado and it's important to have a heater here (especially when the wife is with me). I bought a new thermostat and am ready to put it in (195 deg.) but if this doesn't do it do you guys have any suggestions? Also, how can I increase the blower flow. It doesn't seem to put out a lot of air as well.

XJ Stryker

Heater core prolly stopped off. Try back flushing it.

Pull off the both heater hoses and run water through the bottom one. with a Low Pressure water hose, till it comes out the top, You can repeat cycling from bottom to top till you get good flow.

If you get heat from that and then it goes out again your Heater core will need to be changed, but cycling water is a quick fix that could work out for a while or maybe a few hours depends on how bad it it.

If that doesnt fix it then there is something else you could do but memory escapes me on what the dothingy is someone else I am sure will chime in though.

J8S890

Check:

• a) coolant topped off? (no leaks?)
• b) fan clutch working properly? (i.e. bad one might 'over cool' the system if stuck in 'engaged' mode)
• c) water pump working? (i.e. is coolant actually flowing? belt?)
• d) thermostat working? (i.e. thermostat stuck in open position may over cool)
• e) in-cab (inside) heater controls all ok? (mech. & vacuum?) working (i.e. air flow mixture of hot and cold air correct?)
• f) heater core valve working properly? (engine compartment)
• g) heater core clogged? (see back flushing notice elsewhere in this thread, coolant may not flow through core)
• h) windows all in closed position? (OK, that one was for fun!)

Good luck,

AR.

Mountain Mule

Oh MAN!! o.k. I just closed the windows, it's o.k. now. Okay I'll back flush it and see if that works. What about fan blower? is there an aftermarket blower that puts out more air?

BuckB91XJ

Try the 195 degree T-stat, first. It is a common practice to put 180 degree T-stats to help overheating in the summer and in hot climates, in XJs. A past owner may have done this or you'rs just may be stuck open. Flush your heater core and ensure your Heater Control valve is opening and closing like it should. Your heater blower in an XJ puts out plenty of air when it is working right. Sounds like your is bad if it's putting out weak air flow.

Mountain Mule

Replaced t-stat,(195)
Moved dash selector from hot to cold and back again, no movement on heater control valve, should I replace valve, or find someone with a vacuum checker thingamajig? (sorry, I know how to fix things and what to use, but I don't know correct names for most of them). When I depress the valve manually, it cools down. When I release it, It warms up but doesn't blow real hot... As soon as I can run water through my garden hose (Lines are winterized), I'll flush the heater core. By the way, What IS the name of that vacuum tester?

farmfuel

The brand name is Mighty Vac- all it is, is a hand held vacuum pump. This can be bought at Northern Tools, Napa, Harbor Freight tools, etc.

It sounds like your problem is in the vacuum switch behind the dash. first check all of your vacuum lines running into the fire wall (by where the heater core hoses and evaporator lines run in- be sure it's getting manifold vacuum.) There's a few vacuum lines running in there. Vacuum is supplied to the switch. The vacuum switch will also fill a vacuum resivor/diaphragm that will open the blender door. These doors are usually spring loaded to be closed in one position, then vacuum opens them into another. The blender door needs to be open in the correct position so as to allow air from the blower motor to force air over the heater core, and not force air over the evaporator. Climb under there and watch the door open as you command the heat on. Assuming the door is open to allow air to blow over the heater core, you can always bypass the heater core.

Write back with what you find. It could be as simple as a cracked vacuum line in the engine compartment. If not, you'll probably be needing to tear into your dash. I had this same problem in my 84 Cheif.

Mountain Mule

O.k. thanks alot, that was real informative. I'll get on that. I have a harbor freight right next to me.