# Heater works.....occasionally

**URL:** <https://community.cartalk.com/t/heater-works-occasionally/56646>\
**Category:** Maintenance/Repairs\
**Tags:** hyundai, heating, elantra\
**Created:** [October 20, 2010, 7:31pm UTC](https://community.cartalk.com/t/heater-works-occasionally/56646 "2010-10-20T19:31:00Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Keefe1](https://avatars.discourse-cdn.com/v4/letter/k/4da419/32.png) [@Keefe1](https://community.cartalk.com/u/Keefe1)\
**Post date:** [October 20, 2010, 7:31pm UTC](https://community.cartalk.com/t/heater-works-occasionally/56646/1 "2010-10-20T19:31:00Z")

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My wife has a 2005 Hyundai Elantra GT. Recently she told me the heater hasn’t been working properly for a few months, which oddly enough is right around the end of winter. It won’t get warm while idling or while driving at slow speed. Once on the autobahn it gets nice and toasty then when driving slow again it goes back to not working. What could this be?

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**Author:** ![DfromSD](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/dfromsd/32/1669_2.png) [@DfromSD](https://community.cartalk.com/u/DfromSD)\
**Post date:** [October 20, 2010, 8:07pm UTC](https://community.cartalk.com/t/heater-works-occasionally/56646/2 "2010-10-20T20:07:17Z")

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Have you checked the coolant level? If it’s not low you may have a clogged cooling system. A flush of it may do the trick, or you may need a heater core.

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**Author:** ![researcher](https://avatars.discourse-cdn.com/v4/letter/r/edb3f5/32.png) [@researcher](https://community.cartalk.com/u/researcher)\
**Post date:** [October 20, 2010, 10:13pm UTC](https://community.cartalk.com/t/heater-works-occasionally/56646/3 "2010-10-20T22:13:31Z")

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In addition to the above, replace the thermostat. Does the engine temperature gauge start out low and come up to normal on the autobahn? That would also be an indiactor of a thermostat that is stuck open.

If the cooling system was serviced recently with a coolant change, it is possible that there is air trapped in the heat core and coolant lines. This too would cause intermitant heater operation.

Hope this helps.

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**Author:** ![Keefe1](https://avatars.discourse-cdn.com/v4/letter/k/4da419/32.png) [@Keefe1](https://community.cartalk.com/u/Keefe1)\
**Post date:** [October 21, 2010, 10:26am UTC](https://community.cartalk.com/t/heater-works-occasionally/56646/4 "2010-10-21T10:26:26Z")

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The temp. gauge seems to work normally. I’ll flush the system this weekend and see how that works. If no change then I’ll order a new thermostat. Thanks.