the heater in my 1990 jeep cherokee seems to be blowing cold air, and everyone is telling me its my heater core but not only have a checked it i have also replaced it and it still gives me the same result ... What should i be doing to find out what is wrong with my jeep

 

Is your radiator full of coolant? Thermostat OK? Temp gauage coming up to 200 degrees or so? No air pockets in the system? Good radiator cap?

Heater hoses hooked up correctly? Are they getting hot? Water control valve working?

Good insulation on heater case blend doors? Blend doors working properly?

Temp control panel working properly?

 

Ok i looked at all the following and ty by the way.. and now need a vaccume diaphram. by any chance would you know where to find one for a 1990 jeep cherokee?

 

If you have Jeep dealership in your area, that hasn't gone out of business yet, call them. Check local parts houses. Or go find one in a salvage yard.

 

It's the water control valve on the hose over the fan motor, passenger side, vacuum activated. Try to vacuum it directly from the intake manifold, and see what happens. U probably have a leak where the pipeline enters the vacuum tank (behind the bumper) where it goes through the frame under the light housing.
Google "1990 cherokee vacuum diagram" for the diagram.

 

You can just remove the valve and plug the hoses directly into the heater core...

 

Then the heater will be fighting the A/C all the time.

The heater will win.

 

If you don't have A/C and no doors...then your good to go.

 

Thats true, but the OP didn't say that his Jeep was that way. If it was, he probably wouldn't be too worried about a cold heater, right?

Either he or someone else could read your post, do the mod as you suggested, and then spend many hours and $$$$ trying to "fix" the A/C.

My point is, be careful what you post.

 

If he is worried about cold air coming from the heater...than I helped him solve his issue....

He doesn't make any mention anything about a/c

 

He also doesn't say anything about not having doors on it.

The great majority of Cherokees came with A/C and doors.

Therefore, friendly advice should be tailored to the normal, majority setup.

Just sayin'.

 

but when u say cold air u mean ac cold or just that the heater doesn't work?

 

Thank you all for your replies, and while looking at all this i learned thats its not my heater blowing cold air ... nothing works.... its only blowing the temp of air from outside the car, doesnt matter what im on, what may cuase this issue?

 

I can not seem to find my main source of vacuum in my car can anyone tell me where it is?

 

My car only blows air out from the defroster and not the dash, what should i check to solve this issue?