Heater problems- won't maintain temperature

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McMac
Posts: 37
Joined: Wed Jan 14, 2015 7:47 pm
Location: Washington State

Heater problems- won't maintain temperature

Postby McMac » Sat Jul 04, 2020 12:03 pm

The heater has never worked 100% correctly for me. It got to the point a couple of years ago that I could only have all heat or no heat, but nothing in between. Then it got to the point where there was no heat, just outside air. The secondary coolant pump was changed back then and it seemed to kind of work for awhile.

This last winter it started acting up again- no middle range, just all or no heat. Dealership didn't seem to have any solid solutions, but I decided to have them change the secondary coolant pump again and this time I had them also change the 4 actuators- 2 intake mix doors and 2 mode doors.They did say that a control assembly board (pn 27500-9CH1B) was bad and replaced that too. Now, for example, when I set the heat to 74 degrees, it'll go to that temperature just fine, but it will only hold for a minute or 2 and then the warm air starts cooling off. So I turn it up a few more degrees and it goes to that new temp, but starts to slip again. It'll do this all the way up until the heat is at max and then it will hold. So again, it really is all or no heat. This is all on the manual setting, I've never used the auto setting for heating and cooling.

Dealership doesn't seem to have any other ideas. They suggested I leave car with them so they can duplicate the problem, but it feels like a shot in the dark from them.

Any help appreciated. Thanks in advance.


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smj999smj
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Re: Heater problems- won't maintain temperature

Postby smj999smj » Sat Jul 04, 2020 6:40 pm

I remember someone having some similar issues a long while back and they fixed it by cleaning the intake air temp sensor and fan. To the right of the steering column, you'll see a vent and behind it is the sensor and a small fan, if I remember correctly. He removed it and cleaned it out and problem solved. It's a shot in the dark!

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ShipFixer
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Location: Arlington, VA

Re: Heater problems- won't maintain temperature

Postby ShipFixer » Thu Jul 09, 2020 7:24 am

I have a new sensor but it looks like a minor pain to install, so I just tried cleaning mine first. If you look inside the grill covering the sensor, I am 99% sure you will see it's covered in dust. The dust covered thing in the middle is the thermistor, and the dust covered thing behind that is a tiny little rotary fan that sucks in air through that grill, past the thermistor, and then exhausts it down towards your feet.

I used a combination of canned air and a small, powerful vacuum to clean it. It's somewhat better at monitoring internal temperature. These things have never been really awesome at it, but I will say after driving for 10-15 minutes and getting temperatures equalized, it does hold whatever temperature it believes it's at reasonably well.

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McMac
Posts: 37
Joined: Wed Jan 14, 2015 7:47 pm
Location: Washington State

Re: Heater problems- won't maintain temperature

Postby McMac » Tue Jul 14, 2020 12:10 pm

Thanks for both those replies. I did get the new sensor and it does look like a minor pain to replace. I've been looking at Chilton and the FSM to get in there- I think I'll at least take a run at replacing it. I may end up just trying to clean it.

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ShipFixer
Posts: 613
Joined: Sun May 24, 2009 9:52 am
Location: Arlington, VA

Re: Heater problems- won't maintain temperature

Postby ShipFixer » Tue Jul 14, 2020 7:46 pm

Cleaning it took minutes. It was very, very fuzzy but almost all of it came off very quickly!


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