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Heater Core/ Heater Door malfunction

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Heater Core/ Heater Door malfunction

Old 11-12-2009, 03:13 PM
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Join Date: Nov 2009
Location: Northboro Mass. In Williamsport PA for college right now.
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Default Heater Core/ Heater Door malfunction

Hey guys.

I have a 98 A4 2.8 Quattro sport and I have had a major problem with the heater/ heater core. I have never gotten the heat to fully work in my car. When I turn it on, it blows air at about 65 degrees. It is pretty cold.

I have recently looked at videos about taking the heater core out and can pull it off in about 12 hours by myself. I need to know if the door to the heater vents is stuck or if the heater core is gone.

I have gotten the heat to work for a few minutes once but once the temp was messed with everything shut down.

Please let me know what the best option is. Thanks guys

Old 11-12-2009, 06:09 PM
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Join Date: Mar 2009
Posts: 96

As you probably know, the heater core is a major pain in the you know what. I'm actually in the middle of replacing mine. I've posted some info and pictures if you look for a post by me.

You have a good question. It could be possible the automatic heating unit isn't sending the message to open the flow of hot coolant to the core. The other problem could be the core is just clogged.

You could take the hoses off the core and blow compressed air through it to see if it forces the coolant out. Be very carful when taking the hoses off the core nipples. I just went through this and ended up breaking the brittle nipples.

You could then flush fresh water through the inlet side and see if it flows through smoothly.

After your car is warmed up,
You could also try feeling the inlet and return hoses at the nipples to see if they are hot. If the inlet side is hot but the return isn't, it would most likely be your core is clogged.
If both are cold, the hot water is never making it there and there is some other issue.
Old 11-12-2009, 06:16 PM
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Join Date: Oct 2009
Posts: 147

It is also possible that the flapper valve (for lack of a better word at the moment) that controls the flow of water into the core is stuck. Open the hood, and watch the valve at the hot water inlet side hose to see if it opens/shuts when someone turns the temp from cold to hot and back. Could be a kink in the control wire, a vacuum leak, or just a stuck valve.
Old 12-09-2009, 04:00 PM
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Join Date: Nov 2009
Location: Northboro Mass. In Williamsport PA for college right now.
Posts: 9

I looked around and found heater core flush. I ran it through the car a bunch of times and it seems to have worked. Large chunks of gunk came out of the heater core and I now get heat when the car is running above 2000 rpms..

It is not burning hot though... Just warm...

I have a few questions though,

1) I blew some water through the lines and it seemed that the heater core had a chamber up top and the air was not going throught the lines but it seemed like it was in a chamber up top... Not too sure why...
It seemed to go away a little bit after the flush but not too much...

What is up with that...

2) The heat is not hot... just warm... so what could take the heat to the next level... to work at a normal operating rpm?

Thanks guys for the help.

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