Hey guys. Winter in Kentucky is full force (My favorite time of year). Anyway, I'm having heat issues in my 99 Cherokee sport. I have flushed the heater core and cooling system twice, new blower motor resistor, new 210 thermostat, radiator cap and all new coolant. Both heater hoses are hot and the blower motor fine. However, my heat just isn't warm as it should be, or at least I think it should be. After about 20 minutes it is finally warm enough inside the cab to melt the frost off the windows, but certainly not "toasty." Is there something I am missing? Maybe I am just expecting too much? Sorry if this has been covered before, I searched the old threads but couldn't find anything. Thanks in advance!!

 

The heater control valve is Vacuum operated. I would make sure it is going all the way to the Hot section. May have to replace it. I do not know how all the vacuum stuff works but I have heard of people changing that part out with mixed results.

Anyway Just a thought.

Radcliff, Ky here.

 

x2 on the heater control valve. Have someone inside the vehicle switch the controls from cold to hot and see if the valve arm moves, or if there is a vacuum leak. If it does, the valve may be gunked up inside and just needs to be replaced.

Just replaced mine because I broke 2 of the elbows off when redoing my valve cover gasket. It's about $17 at advance auto - takes 5 minutes to replace.

 

'99s don't have a vacuum heater control valve. Have u verified the coolant temp with something other than the factory dash gauge? New t-stats have been known to be bad. Always a good idea to test it before the install.

 

How to they control the flow of hot coolant to the core?

 

OBSTRUCTED COOLANT FLOW Possible locations
or causes of obstructed coolant flow:
† Pinched or kinked heater hoses.
† Improper heater hose routing.
† Plugged heater hoses or supply and return ports
at the cooling system connections.
† A plugged heater core.
If proper coolant flow through the cooling system is
verified, and heater outlet air temperature is still
low, a mechanical problem may exist.
MECHANICAL PROBLEMS Possible locations or
causes of insufficient heat:
† An obstructed cowl air intake.
† Obstructed heater system outlets.
† A blend-air door not functioning properly.

 

On '98 & later, if the water pump is turning, coolant flows thru the heater core (unless something is plugged or water pump is bad).

 

Im getting the same problem from my 2000 XJ?! tired of replacing things without any results. Any ideas?

 

It's going to warm up Saturday!
Flemming County, KY here.....

 

Sounds like Saturday will be a good day to try and fix it. Again. One other thing that I just remembered was that during the summer, when I would get on the interstate at about 70mph and set the cruise with the AC on, sometimes (usually going uphill) the AC would go wild, and usually redirect itself from the frontal setting to the defrost setting. I could either reset it manually or it would correct itself automatically after a minute or so. I know it is some sort of vacuum leak but I have no idea where to find it. Could it be related in some way?

Also, does anyone have diagrams of the vacuum system or blend door/heater core repairs?

Oh, and BTW, Adair county, Ky here...

 

I'm havin the same problem with my 98. Not the heat issue but heater randomly switches back and forth from the front vents to the defrost vents.. I'm from Pulaski county, Ky

 

Sounds like an interior directional control issue, check water lines going into firewall to heater core, if warm/hot.......theres a duct work issue

 

assuming you have an AC system as well...

 

'98? So '97's still use the vacuum control?

 

i would check out the vacuum lines going to the "ball" in the front of the engine as well.