Heater blowing out cold air

OMAR'SDTS

MEMBER
2002 CADILLAC DEVILLE DTS
4.6L
V8
2WD
AUTOMATIC
103,795 MILES

My car's heater blows out cold air and the A/C works fine, just no hot air.

Wednesday, March 17th, 2021 AT 6:54 AM

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

There are normally a couple reasons for this. Here are some guides that will help with this:

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

https://youtu.be/SNRb6pSwYuU

Clearly the most likely cause of this is a blend door issue so let's start with that.

https://youtu.be/Eqf-H3COtSo

Below you will find the process from the manual. If it were me, I would start with this after you check the heater hoses going into the heater core. Turn the engine on and get it hot and then put the heat on full hot and then feel both hoses. They should be hot. If they are not then we have a coolant flow issue. Either the heater core itself if one hose is hot, or a supply issue.

Let me know if you have questions. Thanks

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