the heater core was just replaced in my 1990 cherokee i just got, well when you turn the heater on it still blows cold air. it does not leak at all so im wondering if it has to do with the switch? any ideas?

 

anybody?

 

Does your XJ have a heater/water control valve under the hood? If the heater core is new, sounds like there's no hot water flowing thru it.

 

sorry man what does that look like?

 

its a black valve with 4 h-hoses & 1 vac line to it on pass sede firewall.

 

so really thats all what allows fluid to go into the heater core?

 

Some models have that water flow control valve, some don't. If yours has it, I'd consider replacing it.

 

and if it doesnt what would that mean?

 

ok i just went and looked, didnt see any black valve.

 

sorry dude mines a 95. i replaced mine last winter. was leaking a bit. yours might b different being a 90. follow heater hoses each way and u'll find a valve sumwhere.

 

here's something else to check... warm up the vehicle, then feel both heater hoses going to the firewall- if they're both hot then you have fluid flowing through the heater core. If one is hot and the other is cool then you have blockage. You should have that valve and it will have a cable attached to it that's coming from the heater controls from inside the vehicle.maybe the cable has become detached.

 

about how big is it?

 

ok here is the deal, i found it and it is opening and closing normally so what else could be wrong?

 

It's remotely possible that a weak water pump can cause poor heater performance (according to the FSM). And if that were the case, u would think with a weak water pump, u would be overheating this time of year. If there's a restriction/reduction (even a small one) in the water flow anywhere between the t-stat housing outlet and the water pump inlet, heater performance could suffer.

 

I have a 90 limited and it is worked off vacuum and the pink plastic line is deteriorating and causes my heater to stop working. is yours cable or vacuum?