Problems with Heater

[redwrangler02]

This is less than the ideal time to be having issues with my heater what with it being winter, so I need some help! Here's the deal:

I have a 2002 Jeep Wrangler Sport with 109k

It has stock A/C and heat

Now, when I have the heat turned all the way to ON, it will seemingly randomly just not blow hot air.

The engine (when I turn the heater on) sits at its normal 210 degree mark

The heater will blow hot air about half the time, and I have noticed quite a few times that it quits blowing the hot air when I am sitting idle at a stop light.

The heater also does this when I am driving so I'm not sure if it has anything to do with the engine working harder.

The fan never stops blowing, it will just start to get gradually colder (over 10 seconds or so) until it is blowing completely hot air, even though I have it set to be as hot as possible.

It is very random but fluctuates like this pretty constantly.

Any input or help is greatly appreciated. I have done a bit of research, narrowing it down to MAYBE the heater core or thermometer/thermostat(?)

 

[JPNinPA]

So just to clarify first. Your heater fan blows air (cold or hot) out the correct vents at all settings? The air is sometimes hot and sometimes cold when the jeep is at temp (210)?

If this is the case it sounds like your heater core may be blocked. Feel the heater hoses near the engine and near the firewall. Are they the same temp by touch? If not detach the heater hoses near the engine and flush the heater core out as good as you could and change the fluids and see where you are.

 

[redwrangler02]

Yes, the fans all blow correctly 100% of the time. And yes, the air (when I have it set to HOT) may blow hot air or it may blow cold air. It will never stay on one or the other when it is set to blow hot; it goes from hot to cold, back and forth, randomly and often. I will check the heater core hoses and fluid. What could be blocking the heater core?

 

[SteelHeadz]

There's a possibility that the issue is on the controls rather than the heater core. If the heater core is already hot, it's impossible to go back to cold in an instant, back and forth as you described. It's more likely that there is an issue with the vacuum switch or the lines that runs to the actuators causing the blend door to open and close intermittently.

 

[JPNinPA]

Corrosion. Have you ever flushed out the radiator or just changed fluid? Over time the coolant brakes down and could become acidic etching away at the block and other soft metal components. Air in the system is another big bad for enhancing corrosion. Air in certain areas could slow or even stop flow.

If you do flush it and see dirty water coming out don’t stop there. Keep pushing water thru until it’s clear. You might flush your radiator after this as the bottom of the radiator may have buildup. After it’s good and clear let it run for 5 min with just water and drain. Refill with the correct fluid mixture.

Be sure when your all done to burp the air out of the system.

 

[degolyerent]

Flush system if you have not done it before, change cap, and make sure system is full of proper coolant
I had same problem with 2003 chevy impala and the cap was bad!

 

[degolyerent]

I should also say if that does not take care of it it will be something to do with vacuum switch or vacuum hose as said by previous post, because heater systems are simple in design

 

[redwrangler02]

Not sure if this helps with narrowing it down, but I've noticed that my engine is running just a bit hotter than it usually does, at least according to the thermometer. It usually runs 210 on the nose, and now it sits maybe 8 or 10 degrees above that. You guys are all correct so far, I have never flushed or even changed my radiator fluid, nor have i checked the cap. I will also check the vacuum switch. Thank goodness I got a Hanes manual when I bought my Jeep, because I'm not sure how to troubleshoot that to tell whether it's working correctly or not. I think I will probably just flush the radiator just to be sure as well. I have a buddy who just replaced the radiator on his Mazda who I'm sure would be willing to help me for a 12 pack . If you guys have any other ideas I'm all ears.

 

[superj]

do the flush, even if hte heater starts working but i agree with steelheadz, the heat won;t go from hot to cold that fast. i think you have a control issue like a blend door or a vacuum line or something.

 

[redwrangler02]

Ok, I hope that stuff (blend door and vacuum line) is in the Hanes manual haha

 

[superj]

how does he under dash on the passenger side of your jeep look? i could tell you really easy where to look on the a yj but i don' know your jeep really well. can you take a pic from the foot area on the passenger side of the bottom of the dash above the passenger foot area and under the center part of your dash? we could probably tell you were to put a piece of safety wire or tie wire to hold the doors so you have heat all the time

 

[superj]

i have to reach under and move mine by hand because my lever is not moving the little door also.

 

[JPNinPA]

I had a vehicle that would blow hot air after revving the engine or after loading it. Air in the system will not allow normal flow, with loading the engine the hot water pushes past and you get a burst of some heat out of the vents. Within a min the flowing air cools the heater core until another blast of hot coolant.
I'm not disagreeing just sharing the experience.


PS it was a blocked radiator and system not filled all the way. I ignored it an dsoon after I replaced the engine. :-(

 

[redwrangler02]

Sorry about the quality, these were taken with my phone in the dark parking lot while I am at work. I hope what you need to see is captured in Tue photos. If not let me know and I can retake them with my digital camera when I get home.

 

[redwrangler02]

Also sorry a few posted twice, I had to upload them with my phone also due to the firewall at work. But great job on the Android app which made this possible!

 

[JPNinPA]

This is the vacuum line they are referring to. The line comes out of the intake across the firewall and enters the cab near the PCM. The rubber connecors are usually what fails. Although, I would think you would only have one vent output no matter what vent setting you selected, if the vacuum line failed. Worth looking into though.

 

[superj]

your jeep is set up different then mine. so i cannot help with those pics. i don't even see any doors

 

[lambo]

I read this on another post and tried it. Now I have great heat. Go to your local self serve car wash. Pull the hoses from the heater valve use the hose without pulling the trigger and flush out the heater core - both hoses till it runs clear. I'm not sure if this is your problem but it worked for me. Also if your belt is loose it will not let the water pump work to its full function and you will not have much pressure. Good luck I'm in Massachusetts and its colder that a witches t!t. So I know what its like to be cold, Not very nice.. also if you think you have air in the system park the Jeep on an incline so the radiator is up higher then the heater core pop of the radiator cap and rev the engine all the air should work its way to the top of radiator and out of system while the Jeep is still running it helps to squeeze the hoses to force air out. Another thing that other members have said about vacuum hoses, on the heater valve is a vacuum hose if you pull the hose of while running the engine you will see a small silver rod move down this is the vacuum plunger it opens and closes when you slide heat controls from cold to hot opening the doors for air flow, this is a very easy way to check vacuum.

 

[SteelHeadz]

It appears from this picture that the door actuator is electronic, not a vacuum controled actuator. there's 2 or maybe 3 screws holding this to the HVAC housing. If you remove this, you should be able to move the door open and close manually by hand. If there's any obstruction or binding, you will feel it.

 

[tp=n=yj]

remove radiator cap .start engine let run til warm .have someone step on gas a little.this causes antifreeze to go to heater core.thats why you get heat when you drive.you will see ratiator will be low add antifreeze while steping on gas petal . then put cap back on. you will have heat nowinjoy