• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Heater fan blows hard on cool but very little on hot

J

Jed

NAXJA Forum User
Location
Alabama
I can turn my fan on HIGH with the slide on cool/cold and there is tons of air that blows out of the vents. When I move the bar over to heat/hot the volume of air is cut in half. I can hear the fan roar but very little air is coming out. For the few of you that have changed the heater core, was there alot of trash behind the heater core? I can't figure out what's choking off the air flow.
any ideas??
thanks
 
What year jeep you got? Most of the heater controls I have used that are vac vontroled have a side effect. Heat will not blow through the regular vents. On the hot temp setting almost all if not all hot air will come out of the heater vents by your feet and or the defrost vents, but not out of the regular vents. As far as alot of trash behind the heater core I myself had none at all. There really is no way to get trash back there unless a seal is bad on the firewall.
 
Sorry about that, I thought I had a sig set up. Mine is an 87 model. The door is controled by a cable. I took the cable off and worked it by hand. It seems to be getting full motion with the cable.
Mine does blow from the selected vent (defrost, floor or vent) it just the volume is very low.....when the temp selector is on hot. Wander if someone has had it apart before and mucked something up..?

thanks for the reply
 
Not sure but the air has to go through the A/C evaporator first before it goes through the heater core. I suppose some foam could have come off the door and ended up in the heater core but would be rare.

So do you get more airflow when you do it manually?
 
MJR said:
Not sure but the air has to go through the A/C evaporator first before it goes through the heater core. I suppose some foam could have come off the door and ended up in the heater core but would be rare.

So do you get more airflow when you do it manually?
Click to expand...

I get the same amount of air when I work the door manually. Wander if there is anyway to get a peek in there without taking half the dash out.....
 
Jed said:
I see I'm not the only one that has had this problem before :wierd: . If I took out the AC evaporator (not sure how it comes out) could I get an air hose in front of the heater core to blow it out?
Click to expand...

You have to pull the dash and whole housing out to get in it. This means discharging the A/C. It's not really difficult just time consuming if you haven't do it before.
 
Thanks for the help MJR & Magimerlin. I think I've done about all I can do without pulling everything apart (I don't think would help either). I drilled a couple holes in the hc housing (easy to plug). I stuck an air hose and blew it out real well which I think helped some. I also found where air was leaking between the fan and hc which would be cold air. It is what it is, by design. The heater core has very very tight vins which makes it hard for air to flow through. That could be the reason I have seen many threads about heater fan up-grade. Maybe I could take out the heater fan and stick a leaf blower in there..... I could make the sticky section yet :laugh:
 
I've got the same problem, but I'm convinced this is a vacuum leak and not a door problem. My fan will blow on heat, and I get a little warm air when I'm sitting at idle...but once I start to move the air flow cuts in half and the heat goes away. I'm a few days away from tracking the problem down, but I'm relatively sure that once I start tracking down the vacuum lines I'll find a leak. I've got an 89 and it should be alot like your 87. Lets keep this post alive or PM each other with our findings.
 
I just looked on advance auto's web site. Looks like a new blower is only 25 to 30 bucks. I say you buy a new one and see if that helps :laugh3:
 
Bored400 said:
I've got the same problem, but I'm convinced this is a vacuum leak and not a door problem. My fan will blow on heat, and I get a little warm air when I'm sitting at idle...but once I start to move the air flow cuts in half and the heat goes away. I'm a few days away from tracking the problem down, but I'm relatively sure that once I start tracking down the vacuum lines I'll find a leak. I've got an 89 and it should be alot like your 87. Lets keep this post alive or PM each other with our findings.
Click to expand...


By the battery as it always is.
 
You must log in or register to reply here.

Similar threads

Jeepmedic46
Heater core
2
Replies
32
Views
4K
RCP Phx
R
V
High temp woes
2
Replies
21
Views
413
Vitzaa
V
tjmotter
Heater box repair - pics needed
Replies
1
Views
1K
75SV1
7
R
Fan not turning on when hot- fan works!
Replies
2
Views
2K
JMA_2001XJ
J
F
Advice from US Postal RHD owners - heater hoses
Replies
2
Views
2K
fenns7
F
Back
Top