Heater not working it blows cold air?

Good morning.

it sounds like the heater core is clogged. you will need to remove the hoses from the core and flush it with a garden hose and assist with air pressure is you have a compressor. if that does not work, then the heater core must be removed.

Lets go over this guide to be sure

https://www.2carpros.com/articles/car-heater-not-working

Roy

Thanks Roy, I will try flushing the core. If it needs the core, how big of a job is it? Looks like a nightmare! If I cannot do it myself where do I bring it? Dealer?

Neil

It is complicated but not that bad. Try the flushing first and let me know.

Roy

Hi I flushed the core it seemed a little better. One other update if I drive the car for a while and use the heat it works okay but. When I turn it off for a few minutes then restart it the heat works great nice and hot. Can you please explain why this happens. I don't want to do a heater core if its not needed. Thanks,

Neil

Ok, I would start by flushing the core again. You made progress but it sounds like it needs more flushing.

It gets hot because when you shut it off, the heat from the hoses heats up the core temporarily.

Roy

I posted this issue late last year, well here I am again with the same problem. To make a long story short, I took my car to the Honda dealer since I have no heat and they explained that the heater core is clogged and it has calcium buildup, they wanted about $700.00 for a flush. I did a simple water flush with the garden hose last year and bright green coolant came out the other end, no crud or buildup of any sort. I did the same procedure today but a lot more thorough, water flushed it then reverse flushed it, then I poured CLR on one end of the heater core, let it sit for about 15 minutes, then rinsed it out with water and repeated the same step on the other side, with multiple reverse flushes, clean water came out both sides and I still have no heat. Attached are the images I took of the temperatures for each vent and both heater hoses once I put everything back together and let the car run for more than half an hour.

As seen in the pictures, the passenger side vent next to the door has the hottest temperature at 118 degrees, then as you go left past each vent, the temperature gets colder. Pretty weird. Also, the top heater hose reads 152 degrees and the bottom hose reads 168 degrees. Again, these are all temperatures taken after the car had been running for more than half an hour after the flush was done.

I am not convinced that this is not a heater core but there are things that make me question it. Namely the inlet and outlet temperature of the heater core. Normally when it is blocked you have a cold return line. However, we could still have a partially blocked heater core.

I would suggest we remove the air temperature door and manually move it to full hot and hold it there and check your temps again at each vent. I suspect this may be the issue just because you have 168 coming into the heater core but your air temperature is only 118 at the hottest. I anticipate a drop in some temp but not 50 degrees. You may need a helper to do this but once you remove the motor you will be able to move the door with your fingers and put it to max hot. It is full travel one way or the other so just test it in both directions. If you don't get proper heat that is pretty even across all the ducts then the heater core would have to be the issue.

Okay, how do I get access to that motor on the drivers side?

Sorry. I meant to include that process. Here it is from the manual.

Hi everyone,

I am finally back, and with a new ride! Unfortunately, the old Taurus I owned just a few months ago gave out and she blew her AC out, had to get rid of it. I am now driving a sweet car listed above it is an EX-L and I love it so far. However, with winter weathers creeping around the corner, it has been getting pretty chilly outside now and now would be the perfect time to kick the heater on, or so I thought. Having heat in the car is a luxury, the Taurus I owned never had a working heat and I tried every trick in the book over the course of 4 years to fix it with no avail. This car has great AC, but I noticed that when I tried to kick the heat on, the higher I turned the temperature on, the air would start blowing from the windshield defrost and not the vents in front of me, when I kick it down to cool, AC starts coming out perfectly through the vents, any guesses?

I would appreciate it!

Welcome to 2CarPros. And welcome back:

This is an interesting issue because the when you increase the temp, the blend air door actuator is what should react. When you change direction of air flow, there is a different actuator which should respond, the mode door actuator. I think what we should start with is the mode door actuator. What I would like you to do is disconnect it and see if changing the temperature still has an affect on air flow direction. If it does, then we will need to inspect the mode door itself.

The mode actuator is located on the HVAC box under the dash. If you look at the attached picture, I highlighted both the mode door actuator and blend air door (air mix) actuator. You can see they are not close. That is what is causing me confusion.

Regardless, if we find air flow changes after the mode is disconnected, we will have to inspect the door and make sure nothing is loose or disconnected.

Let me know what you find.

Joe

That car uses a parallel flow heater core so you would get good coolant flow through it even if 90% of it were plugged. From the description I would say that you have 3-4 open crossover tubes and the rest are plugged similar to what I put on the image of the core. The coolant flows in, goes across the blue area just fine but the core is blocked from the red line back so no coolant flows through those sections. You get just the heat the small area produces and it will be the hottest air closest to the core, just as you have shown. Totally normal for a plugged parallel core to show the signs you have.

The problem with them is flushing really doesn't work very well because the flush takes the same path as the coolant. I have had limited results with an air and water flush gun and using vinegar to cycle through the core in reverse flow but even then it wasn't real great. The air helps by causing turbulence in the cleaner in the core and gets it in farther to dissolve the calcium and crud. In the end the best solution is usually replacing the heater core.

Thanks for the information! Thankfully I have warranty with my dealer so they will be inspecting it, free of charge, on Saturday morning. I will let you know what they say.

I am definitely going to try and diagnose the blend door actuator first, I really hope I do not have to replace the entire heater core, I have seen the procedure online and it is such a crazy design by Honda.

Welcome back:

Happy to help. Let me know what you find. I'm interested in knowing what they find.

Have a good weekend,

Joe

Back again, I went ahead and looked under the steering wheel to check on the blend door, this is normal right?

Got the call from the dealer just 15 minutes ago, turns out all the actuators and doors are working as they should, it is the heater core that has some calcium build-up which is clogging it and preventing heat from flowing out. They want $570.00 for labor and parts since my warranty plan does not cover the service since it is not a part replacement. Can I do this myself because I don t plan on spending that amount of money?

Yep. Looks like it is moving through its full travel. Normally they have a gear and are not visible but that is pretty clear.

Which takes us back to the heater core. As Steve said these are multipassage so you can have a partial blockage and it causes this issue. The coolant and your flushing will take the path of the least resistance and not remove the blockage.

I have not tried this on a Honda but on some vehicles you can remove the blower motor and see the heater core. If you can, you can use that laser temp meter to see if the entire surface of the heater core is even. I suspect you will have some cold spots which shows it is blocked.

Here s the invoice.