# No Heat, and it's getting cold in minnesota, 1999 Merc. Mountaineer AWD V8

**URL:** <https://community.cartalk.com/t/no-heat-and-its-getting-cold-in-minnesota-1999-merc-mountaineer-awd-v8/7772>\
**Category:** Maintenance/Repairs\
**Created:** [November 28, 2007, 5:29pm UTC](https://community.cartalk.com/t/no-heat-and-its-getting-cold-in-minnesota-1999-merc-mountaineer-awd-v8/7772 "2007-11-28T17:29:42Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Jonnruth123](https://avatars.discourse-cdn.com/v4/letter/j/ee59a6/32.png) [@Jonnruth123](https://community.cartalk.com/u/Jonnruth123)\
**Post date:** [November 28, 2007, 5:29pm UTC](https://community.cartalk.com/t/no-heat-and-its-getting-cold-in-minnesota-1999-merc-mountaineer-awd-v8/7772/1 "2007-11-28T17:29:42Z")

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On a warm day in October, I had my check engine light come on, my temp. guage quit working, and no heat from the registers. I replaced the coolant temp. sensor but that didn’t do it, any ideas?

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**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\
**Post date:** [November 28, 2007, 5:40pm UTC](https://community.cartalk.com/t/no-heat-and-its-getting-cold-in-minnesota-1999-merc-mountaineer-awd-v8/7772/2 "2007-11-28T17:40:45Z")

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Yeah. Your temp gage is probably sitting at the bottom and no heat coming out of the registers because the coolant is staying dead cold. Like as if the thermostat is stuck open. Which it may be. Try changing it.

Have the codes downloaded at Autozone. Post them here.

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**Author:** ![87\_Ranger](https://avatars.discourse-cdn.com/v4/letter/8/f14d63/32.png) [@87\_Ranger](https://community.cartalk.com/u/87_Ranger)\
**Post date:** [November 28, 2007, 6:19pm UTC](https://community.cartalk.com/t/no-heat-and-its-getting-cold-in-minnesota-1999-merc-mountaineer-awd-v8/7772/3 "2007-11-28T18:19:35Z")

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Odds are the trouble code will be PO125 “insufficient coolant temp to enter closed loop.”

Not only will the heater blow cold, but the engine will also be running rich & wasting gas.

As mountainbike mentioned, change the T-stat.

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**Author:** ![Jonnruth123](https://avatars.discourse-cdn.com/v4/letter/j/ee59a6/32.png) [@Jonnruth123](https://community.cartalk.com/u/Jonnruth123)\
**Post date:** [November 30, 2007, 4:31am UTC](https://community.cartalk.com/t/no-heat-and-its-getting-cold-in-minnesota-1999-merc-mountaineer-awd-v8/7772/4 "2007-11-30T04:31:53Z")

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Thanks alot, World Auto Center in Eden Prairie replaced the t-stat and I NOW HAVE HEAT!

Great shop!

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**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\
**Post date:** [November 30, 2007, 6:41pm UTC](https://community.cartalk.com/t/no-heat-and-its-getting-cold-in-minnesota-1999-merc-mountaineer-awd-v8/7772/5 "2007-11-30T18:41:21Z")

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You’re welcome. Thank you so much for the feedback. We rarely get to find out how things turned out.