Heater blows cold air

Tiny
CISSELLA
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 220,000 MILES
The heater in my Jeep is blowing cold air. I had the thermostat replaced about a year ago, and that didn't fix the problem. I just took it to the repair shop and they told me it was because the heater core was clogged with buildup, so the engine coolant was not flowing to the heater core. They flushed the coolant system and said this would fix the problem, but it only fixed it for about a 2 days and is back to blowing cold air again. The repair shop told me it would cost about $900 if I had to replace the heater core, something I'm not really in a position to do. Is there a more agressive way to clean the heater core out, or could it be another problem altogether?
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Wednesday, December 23rd, 2009 AT 6:46 PM

30 Replies

Tiny
IMPALASS
  • EXPERT
Hello -

To better assist you is your model the Cherokee Classic, Limited, SE, Sport, Grand Cherokee Laredo or Grand Limited and what is the engine size in liter.
Do both heater hoses get hot when the engine is warmed up? If so this is an indicator that the flow is there and you may have a blend door issue. For this we will definitely need to know which Jeep you have as the Cherokee and Grands are vastly different

Read this guide, it will help you figure out what is going on

https://www.2carpros.com/articles/car-heater-not-working
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Wednesday, December 23rd, 2009 AT 7:22 PM
Tiny
GUITARMAN296
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 78,000 MILES
I have recently replaced the engine in my vehicle with on that has 78000 miles on it. I now have no heat, only the defrost mode blows air and its cold all the time.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
LJHOPP
  • MEMBER
The reason why the defrost setting is the only one that is working is because that is the default setting when their is a vaccum problem. Check your vaccum lines under your battery a lot of people have reported by fixing that line has solved this problem. Other wise follow the vaccum lines back to the firewall one might not be completely on you may have a crack that is leaking.
Has for you only having cold air blowing out I would check your blend doors. Go to the heater treater website they have videos that will show you how to fix this problem.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
TIESHAY
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 16,000 MILES
My 99 jeep grand cherokee has no heat, the air blows out but blows out cold air. It actually blows out whatever the temperature outside is. If it is hot outside I get hot air if it is cold I get cold air. Please help, no one can tell me what is wrong with it
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
BLACKOP555
  • EXPERT
First feel the heater core hoses with the vehicle hot. They should be hot. Tell me what you find.

Really sounds to me like your blend door is not working in your car and is stuck in the middle of the temp range.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
CONLEYMM2
  • MEMBER
  • 1999 JEEP CHEROKEE
  • V8
  • 4WD
  • AUTOMATIC
  • 70,000 MILES
My Jeep Grand Cherokee Limited has dual heater control (driver and passenger). Driver works fine, but passenger side (defrost, personal, and floor vents) all blow outside air even when you turn the control up to Hi. Change the control from hi to low and back with no change.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
FERRARI 1
  • MEMBER
I had the same problem I had heat only on one side and then no heat on one side. I t was a blend door actuator which was a dealer item and a dealer job to fix. Good luck. The dealer can let you know in a few minutes no charge. If you have them fix it. This is a very common problen only for jeeps from 1999 to 2004 then this system was changed. I personaly think it should have been a recall item. Good luck
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
WILD BILL
  • MEMBER
  • 1999 JEEP CHEROKEE
Heater problem
1999 Jeep Cherokee V6 Four Wheel Drive Automatic 93000 miles

what could cause the heater to not blow heat? Is there a control valve somewhere that could be malfunctional? Blower works fine. Thermostat is fine.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check for clogged-up heater hose and the heater core-could be the heater control valve. Coolant level is up to the full mark?
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
JOHN SCOTT
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
The heater in my 1999 Jeep Cherokee sport does not get hot. The fan works, but it seems the control switch from hot to cool is not funtioning. Air is at best slightly warm (outside above 45 deg) to cold (below 30 deg). Need to know how the flap in the box works, (electrical or vac.) And how to troubleshoot problem.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
FIXITMR
  • MEMBER
Did you check both your heater core hoses to see if they are hot when engine is up to temp?
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
POPS1966
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 96,000 MILES
Air blows freely from all vents. Temperature register up to 210 degrees. Only cold not hot air is blowing thru the vent. Any idea of the problem?
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check the thermostat if it stcuk open and the heater core if its clogged-up, if it has an heater control valve check that too-if all okay-could be door problems, vacuum/actuators and HVAC control module.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
DAMONRE
  • MEMBER
  • 1999 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 156,000 MILES
I have 1999 Jeep Cherokee classic and the heat is not working what can I do? I replace the thermostat.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
CJ MEDEVAC
  • EXPERT
Feel the heater hoses near the firewall, after your rig is at operating temperature. If they are as hot as your upper radiator hose, the thermostat is probably not the problem!

Observations? Other observations?

I do not know your rig well

I will try to help you

I'm still here!

The medic
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
CJ MEDEVAC
  • EXPERT
Are they uncomfortably too hot to hold in your hand very long (all mentioned, after you reach operating temp). Or cooler after it idles a while, and really hotter just after a drive (if you check it quickly after the drive)

Does your temp gauge fluctuate from "higher" while driving to lower while "idling"

You can respond below at "add a reply"

The medic
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
CJ MEDEVAC
  • EXPERT
By the way---i do not know you, so I am not directing this to be mean!

I do this to everybody, who is not "me"!

Did you install the thermostat prior to having this issue or after--even so, is it sitting with the spring down and pointy side up,
Have you had the heater hoses off and maybe misrouted them?

Really good one---are you full of radiator juice?

Is there any sort of "water switch" on the heater hoses---between one end of them, to the other. If there is, maybe its stuck partially shut. It might can be completely removed (now that it's winter time) and the hose replaced in full length or just the valve be replaced with a suitable coupler till you can do better!

Are they old and squishy, and maybe the water-pump is sucking the return flat?

Are there any kinks in the heater hoses?

I'm about to hit the hay--see you in the morn!

I will leave you with some thing to try

Take loose the highest heater hose on the engine--at same time watch the water in your radiator--is it falling as if you just bled the air from an air pocket?

If no results there, continue with this:

Connect a long heater hose from the water pump to the fitting in the engine (completely by-passing the heater core)how hot does this line get?

While that is loose, force water thru the heater core with a water hose---is it flowing freely from the open side?

Heck, if the water hose is connected to every heater hose in the system, (one component at a time) does it come out the opening on the other end of each component

Night--night

That oughtta keep you up all night!

The medic
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
CJ MEDEVAC
  • EXPERT
Sorry, between my 1st and 2nd answer, "damonre" sent me a message, we were discussing the heater hoses and the radiator upper hoses' temperature!

The medic
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
JIMHARVARD
  • MEMBER
  • 2000 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 115,417 MILES
No existing mechanincal problems other than addition of about two pints of cooling fluid monthly. Engine overheated on a local errand. Went home, filled radiator and ran to warm up - still no heat from heater. Oil pressure spiked to 80psi. Checked oil could not see any "bubbles" or water in oil. Oil level drops to correct level when engine is off. No smoke out of exhaust. Purchased new and changed oil every 5-6k miles.
Any suggestions?
Thanks
jim coster, pittsburgh, pa
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)
Tiny
RACEFAN966
  • EXPERT
Ok I would check to see why it using coolant. I would call around and find a shop that can do a chemical test on the radiator to see if it has a blown head gasket this will answer this with no guess work. Now as for the heater these systems are very hard to get full or burp the bubbles out so you may need more coolant you will have to check if all this checks out then get back to me and we will dig deeper into the heater system to see if the heater control valve may be bad. Thanks and Merry Christmas.
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Saturday, January 12th, 2019 AT 5:29 PM (Merged)

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