bigjeff

hi i have a 1999 jeep cherokee with inline 4.0 it blows out hot air once in a while but blows cold all the time i check the blower its working i checked blend doors they are good i think what does the blower restior do could that be it but y do i have hot air sometimes i really need help i got 2 kids 6 year old 4 month old its cold in ny u can e mail me jeffolen@yahoo.com

tiny tim

Thermostat intermittently sticking open?

kjc

The blower resistor only controls the speed of the blower. When they go bad you usually only have the high setting working for the fan. It wouldn't affect the temperature. You said you think the blend doors are ok? Does your heater hose have the vacuum controlled shut-off valve? If so, I'd check that out. From what I've read on here, most people just bypass it and plug the vacuum.

Sideways99

coolant flush, new t stat, cardboard over 1/2 the rad as last resort

viper_venom600gtsr

Is your jeep overheating? Check coolant level. I started off with similar symptoms and turned out to be a cracked 0331 head and was losing coolant without any obvious leaks and ended up finding out when I wasn't getting any hot air and temperature would jump to 220 during normal driving.

byrdman__xj

Have you tried flushing the heater core directly. I had the same problem with no hot air. After I did a flush on the heater core with a flush kit cleaner and compressed air my 95 xj was making me sweat with 19 degree weather. I suggest that.

bigjeff

my heater core is leaking i now it now good but cant figure out y it overheating

tjwalker

Correct in that blower resistor would not result in intermittent temperature; just controls the speed(s) of the blower motor.

Whenever you are symptomatic, you really should review all cooling system components. What is the history of cooling system maintenance?

Everything on the cooling system works in lockstep. Radiator, radiator cap, water pump, fan clutch, thermostat.

If this stuff is all old and you plan on keeping the vehicle, sure you can piecemeal and often get to the root cause but also consider performing a wholesale replacement of all components. If one fails, others are generally not that far behind. That way you have a rebuilt cooling system and peace of mind for you and your family. The parts are not that expensive if you can do the labor yourself.

Replacing that heater core though is a PITA; quite a bit of labor involved.

bigjeff

i took of top raditor hose and ran it for 5 mins untill fan came on twice only steam came out hose so i take the t- stat and try it if nothing comes out then that means water pump the pump is less the 2 months old