89 Comanche Heater Don't Blow Hot For Long

[timberjack]

I have a 89 Comanche and the heater blowes hot for about 10 sec then turns cold. Turn the fan off and it takes about 5 min to get hot again so turn blower back on and same thing. So what am i doing wrong. I made sure the cable driven flow valve was open too. Heater hoses are also not hot going into the heater core.????

 

[ftpiercecracker1]

http://www.cherokeeforum.com/f51/dash-removal-35444/

 

About 3/4 of the way down in this writeup you will find what controls your "blend" door, this is the door that diverts air either to be pulled through the a/c or the heater core. If the diaphram stops working or startings leaking it will only hold the door open for a moment until the vacuum is not strong enough. If it were my truck this is what i would be looking at and yes you have to pull the dash.

 

hopefully someone else will chime in to verify.

[Eagle]

If the hoses leading to and from the heater core don't get hot with the vaccuum valve open and the engine at normal operating temperature, the only answer is that there's no coolant flowing through the heater core. Let's face it, it's 24 years old and probably plugged solid. I kept the heater core on my '88 Cherokee flushed out, and it sprung a leak three years ago. I just blocked it off and ran without a heater for one winter, then I replaced the heater core.

[ftpiercecracker1]

Oh ya, forgot about the vacuum do-hicky, i got rid of mine so long ago i forgot about it  :D .  This thing. . .

 

[timberjack]

Ok thanks all it is about winter over here in Missouri so will check this all out.