I just purchased a 93 2-door and the heater does not seem to work. It does not have the heater control valve and was bypassed. The system was flushed two weeks ago and the heater core does not leek and it has a new fan. It gets to 190 or so I'm at a loss..
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Heater Help
- Thread starter callelk
- Start date
- Location
- In a strange land
When you say "the system was flushed" does that mean the heater core was flushed separately, both directions? That would be my first step.
The second thing to look into is the opening/closing of the doors that control hot/cold airflow through the airbox inside the vehicle.
Also, you mention the presence of a new fan, but is it actually blowing air? There can be issues with the resistor pack, and there can be issues with the plug on the back of the speed settings switch.
The second thing to look into is the opening/closing of the doors that control hot/cold airflow through the airbox inside the vehicle.
Also, you mention the presence of a new fan, but is it actually blowing air? There can be issues with the resistor pack, and there can be issues with the plug on the back of the speed settings switch.
I have the invoice from the work done 12/2021 prior to my purchase. Here is what is says:
Blower motor removed and replaced (does a good job in all fan speed settings)
Replace heater hose and flush system (no heater control valve)
Blower motor resistor removed and replaced
I checked under the dash on the passenger's side and the doors are opening/closing but I get defrost but nothing out of the front vents, only the footwells...sorta...
The temp gauge goes past 180 but no were near 210. But it is 22 deg outside.
It has Air conditioning.
Blower motor removed and replaced (does a good job in all fan speed settings)
Replace heater hose and flush system (no heater control valve)
Blower motor resistor removed and replaced
I checked under the dash on the passenger's side and the doors are opening/closing but I get defrost but nothing out of the front vents, only the footwells...sorta...
The temp gauge goes past 180 but no were near 210. But it is 22 deg outside.
It has Air conditioning.
cruiser54
NAXJA Forum User
- Location
- Prescott, Az
Grab the heater hoses near the firewall.
Are they both hot when the engine is at operating temp? ?
Are they both hot when the engine is at operating temp? ?
I'll check this am when I leave. I'm in the middle of nowhere at a hotel driving it home and its snowing. Fun!
I'm surprised that the heater core was not replaced as he had the a lot of the dash out to put in new light bulbs and a headlight switch. I assume that he did not believe that it was necessary at that point.
cruiser54
NAXJA Forum User
- Location
- Prescott, Az
There's a HUGE difference between replacing those bulbs and headlight switch compared to a heater core replacement!!!!
They can generally be flushed anyways.
They can generally be flushed anyways.
You are up kinda early. Like me and sleep on average of 5 hrs a day?
Very true but the funny thing is on the invoice from the repair shop, it shows the reason it was taken in was the heater did not work. The shop charged almost a grand to do the work and it still does not blow warm/hot air.
Air bubble?
Did not reverse flush? (said it was flushed)
Without the heater control valve, there is nothing i can think of that would stop the hot water from circulating through the heater core.
cruiser54
NAXJA Forum User
- Location
- Prescott, Az
6 hours a night.
Gotta be the heater core then. Check it out.
Gotta be the heater core then. Check it out.
Thanks for all the reply's.
I'll check the hoses this morning before I head home. Once there I will put my Digital Infrared Temperature Gun on the thermostat housing to see what the operating temperature is. May have a stuck open thermostat or a cold one in. Gauge shows a little cold.
If all that checks out I will reverse flush with with CLR and check again.
If that does not cure it then I will replace the core....not looking forward to that.
I'll check the hoses this morning before I head home. Once there I will put my Digital Infrared Temperature Gun on the thermostat housing to see what the operating temperature is. May have a stuck open thermostat or a cold one in. Gauge shows a little cold.
If all that checks out I will reverse flush with with CLR and check again.
If that does not cure it then I will replace the core....not looking forward to that.
howephillip
NAXJA Forum User
- Location
- Vernal, UT
No heat comes from the defrost?
If your engine is running at 180º then your coolant is hot regardless. Hell, at 100º that's still blowing hot air.
If your engine is running at 180º then your coolant is hot regardless. Hell, at 100º that's still blowing hot air.
- Location
- In a strange land
I see two possible issues here, and both could be in play.
For one, you may not be getting flow through the heater core. Disconnecting the hoses (and you can do that at the front of the engine rather than the firewall) and running water through them will tell you whether or not you have coolant flow through the heater core.
Secondly, you may have issues with the doors that control both the blend and the direction of airflow in your heat/AC system. The fact that you can only get defrost suggests something is not working in there. Even if you do not have coolant flow through the heater core you should still get airflow from the fan coming out of the various vents depending on settings. It might be cold air, but something should be moving.
One other remote possibility is that you do not have airflow going over the the heater core. I don't know what would be likely to create that problem--maybe a mouse building a nest or perhaps many years' worth of pine needles working their way into the box--but if something is keeping air from moving across the heater core that could be the issue. Major PITA if so, since it will mean you have to disassemble the entire dash as if to replace the heater core.
ANAX,
I received a text from the previous owner this morning and he stated "he had to play around with the controls to get warm air flowing".
I'm thinking that there is an issue with the blend since there is nothing coming out of the vents, only the defrost but it is cool air. It stands to reason then there is no/limited air flow across the core.
Is there a way to check that? Sorry, new to this and need to crawl before I walk.
I received a text from the previous owner this morning and he stated "he had to play around with the controls to get warm air flowing".
I'm thinking that there is an issue with the blend since there is nothing coming out of the vents, only the defrost but it is cool air. It stands to reason then there is no/limited air flow across the core.
Is there a way to check that? Sorry, new to this and need to crawl before I walk.
- Location
- In a strange land
Yeah, not exactly a job you want to do.
That is the last resort. Made worse by the fact that there are not any really great replacement parts available anymore.
That is the last resort. Made worse by the fact that there are not any really great replacement parts available anymore.
howephillip
NAXJA Forum User
- Location
- Vernal, UT
To be fair, heater core replacement is only difficult if you try and take shortcuts. The dash bolts right off. I just replaced my heater core last month and if I were to do it again I could do it in a couple of hours.
Your problem sounds like it a blend door or vacuum issue. If coolant is going in/out of the core and the fan is blowing then it doesn't matter how hot it gets in this situation because you stated that no hot air is coming in.
Have you removed the HVAC controller and made sure connections are tight?
Your problem sounds like it a blend door or vacuum issue. If coolant is going in/out of the core and the fan is blowing then it doesn't matter how hot it gets in this situation because you stated that no hot air is coming in.
Have you removed the HVAC controller and made sure connections are tight?
How do I check the blend door?
- Location
- In a strange land
If you take a look at some of the Youtube vidoes that include the opening up of the HVAC box you will see where the blend door is located and how it works. The fun part will then be finding the bottom of it underneath the box while it is still installed under the dash.
It makes logical sense that you could have a vacuum problem. That could explain the removal of the heater control valve. It could be that someone got as far as determining that the heater control valve was not being opened/closed by vacuum as it is supposed to be. It could be that they decided to delete that valve rather than fix the vacuum problem. But if the vacuum problem also means the blend door doesn't function then nothing was gained. At that point the owner gave up and decided to sell the Jeep.
It would also be worth checking to make sure that when the heater control valve was deleted the vacuum line to it was properly capped off. I don't know how all those vacuum circuits function, but if you are losing your vacuum to an uncapped line perhaps that would prevent the blend door from being able to operate.
It makes logical sense that you could have a vacuum problem. That could explain the removal of the heater control valve. It could be that someone got as far as determining that the heater control valve was not being opened/closed by vacuum as it is supposed to be. It could be that they decided to delete that valve rather than fix the vacuum problem. But if the vacuum problem also means the blend door doesn't function then nothing was gained. At that point the owner gave up and decided to sell the Jeep.
It would also be worth checking to make sure that when the heater control valve was deleted the vacuum line to it was properly capped off. I don't know how all those vacuum circuits function, but if you are losing your vacuum to an uncapped line perhaps that would prevent the blend door from being able to operate.
cruiser54
NAXJA Forum User
- Location
- Prescott, Az
I believe the blend air door is cable operated through 1996.
