Zaraki

95 Civic DX

I'm only getting lukewarm air right now... and when it's in the 20s or below, I'm freezing my *** off!!!!

things I've done:

new thermostat
new coolant, completely full and bled air in system
manually adjusted the valve on firewall and under dash
flushed heater core

both lines going into and out of the heater core are hot!

Is there something I'm missing? Is there a blend door stuck or something?

TomCat39

When you were looking at the bottom of the heater core box, did you notice any broken flapper posts? There is two 4 way levers down there and if a post is broken going to one of those 4 way levers, the lever will not adjust the flap.

If all flapper posts seem intact and all 4 way levers have all 4 connections without issue, then the problem is very likely leaves and needles have clogged the heater core air flow in the box.

If you don't have AC, you can take out the connector/conduit section between the blower motor box and the heater core box. Put your heat to full max hot temperature and vacuum out the debris that you see. With a toothbrush you migh be able to brush the fins to get more debris out without damage.

Zaraki

Thanks!

All the posts are intact and move back and forth, no issues.

Looks like I'm going to have to take apart the heater box... any tips/tricks? Not trying to break anything.

Dropped the blower motor out and cleaned all the leafs and pine needles outdo that.

TomCat39

You don't have to open up or remove the heater cor box, that is way more work than you would like. You have to remove the dash board.

Like I said, if you don't have AC, then it's a simple conduit between the core box and blower box. 2 bolts holding it in place. Drop that and you can see the air path right to the heater core. you slide the temp control to max and you should see the flap pull away from the core and that is where you will find all the leaves and needles stuck into the core.

Vacuum that out and that should help the air flow through the core.

The other possibility is you don't see the flap pull away from the core and that means there is a piece missing from one of the 4 way levers or the flap itself is busted.

Zaraki

Ok cool

is that located behind the glove box?? Or?

I'll definitely give this a try when I get home, curious to see what I can find in there.

TomCat39

yeah, behind the left side of the glove box while the blower box is behind the right side.



I circled in red where you see the flap that covers the core itself. If you have to pull that flap back by hand, something is wrong.

The pic is where I replaced my heater core during the summer. As you can see, you have to take the dash out.

Zaraki

Thanks dude, really appreciate it!!!

I dropped that portion down and cleaned out some more crap, not really much in there though.
The little flap looks to be working fine too.

I'll be driving the car soon, hopefully I get a little more heat!

TomCat39

Then in all reality, there is no reason for you not to be getting heat if the blower works, the flaps are working and both heater hoses are getting hot.

This indicates flow, no reason for no air flow through the core and the flapper/heater core box is working correctly.

Zaraki

Yep, still just getting lukewarm air.... No improvement.

I'm all out of ideas.... Maybe an issue with the heater core, since that's the only thing I haven't replaced. How hot should the hoses going in and out of the firewall get?

TomCat39

Borderline burn your hand hot, assuming you have temp set to max hot.

If you have the temp selector to max hot, the hoses should get just as hot as the two main hoses to the radiator.

If they don't then yeah, your heater core is clogged up and restricting flow.

Zaraki

Well they're both getting good and hot... doesn't make sense.

I'm pretty much giving up lol

TomCat39

Did you physically see the heater core when you had that portion dropped?

I made an error, there is one 4 way lever and there should be 3 white plastic sliders pieces connecting flap door posts to the lever. I have circled them in red.



Then when you had the portion dropped you should have been able to see the core when the door was open (heat selector to max hot), I also circled in red.

94 Civic Si

Possible there are deposits affecting the heat transfer in the core?

Is CLR a good product to soak the inside of the core with?

Zaraki

Yeah, when I dropped that portion I could see the core. I could move the flap back and forth using the lever without issue too, so I know it was not stuck. Some debris around the core but not much, most of it came out when I dropped the blower.

TomCat39

And do you have all the sliders connected to the 4 way lever under the heater box?

I noticed in the illustration, there there is also a flapper door on the back side of the core that you can't see. Notice how it's sitting closed on the heater core in the right pictures on the second attachment I posted above?

If none of these are a problem then a severely restricted flow heater core is all that is left. I would think the heater hoses wouldn't get so hot but I guess a little flow allows them to heat up appropriately.

Warby

i have 08 civic with similar issues but with a twist. Driver side vents hot and then middle vents cooler with far right passenger vent cold. Replaced heater core after flush did not help. Thank you Dealer for taking my money with no change! AC worked fine in fall. Is EX model. I have limited skills so other than what I can see, will have to pay someone to fix. Just don't want to get hosed again, just need passenger heat,

Warby

i have 08 civic with similar issues but with a twist. Driver side vents hot and then middle vents cooler with far right passenger vent cold. Replaced heater core after flush did not help. Thank you Dealer for taking my money with no change! AC worked fine in fall. Is EX model. I have limited skills so other than what I can see, will have to pay someone to fix. Just don't want to get hosed again, just need passenger heat,

tony_2018

What about the valve on the heater hose? Is it opening up when you move the lever inside?

Warby

I'm pretty sure it is as the driver side vent feels like maximum Heat after about 5-10 minutes on the road. Just not sure why the far-right vent on the passenger side is ice cold. If I turn on the recirculation button it does warm up slightly so I'm thinking somehow maybe that's taking air directly from the outside???

TomCat39

The 2008 is totally different than the 1995. You cannot compare the two.

Even from 1996-2000 the directional control was fully motorized while the 92-95 is mainly mechanical with the exception of one motor controlled by vent buttons.

You should post your issue in the 2008 section and reference this thread in the 92-00 section if you think it's relevant.

tony_2018

If you're getting heat than your issue is with the heater core control box, the flaps inside are probably fucked.

Zaraki

Back from the dead. I’m still stumped on this issue.

I drove the car for about 2 hours today (about 40 degrees out) and only managed luke warm air at best.
When I got home, I felt both hoses going to and from the heater core and they were hot.

Over the summer, I replaced the radiator and did new fluid again.
I’ve bled the system countless times just to make sure there’s no air in it.

TomCat39

I don't remember and I'm too lazy to spend any significant time re-reading the whole thread. And you know exactly what you've done so far soooooo.

Did you ever inspect your flapper box that houses the heater core?

And, do you have AC?

Zaraki

If I put some type of radiator flush in, would that be enough to flush my heater core and dissolve any buildup?
I feel like it must be partially clogged.

Zaraki

Yes, all flappers and levers are functioning properly.

Nope, no AC. It’s a 95 DX