# Do I have a bad thermocoupler? **URL:** \ **Category:** Factual Questions\ **Created:** [November 21, 2010, 11:57pm UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489 "2010-11-21T23:57:31Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [November 21, 2010, 11:57pm UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/1 "2010-11-21T23:57:31Z")
First of all, I am pretty sure the pilot light problem is not a draft. The water heater pilot goes out during extremely cold winter nights. My thought is that the thermocoupler itself gets so cold those nights, the pilot cannot keep it warm enough to read that the pilot flame is on. Can it get so cold that a thermocoupler reads that the pilot is out even if it is on? Is it a sign of a bad thermocoupler or is there another fix I should look at. ---
**Author:** ![Snnipe\_70E](https://avatars.discourse-cdn.com/v4/letter/s/b5a626/32.png) [@Snnipe\_70E](https://boards.straightdope.com/u/Snnipe_70E)\ **Post date:** [November 22, 2010, 12:31am UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/2 "2010-11-22T00:31:21Z")
> [@Saint\_Cad](#): > > First of all, I am pretty sure the pilot light problem is not a draft. The water heater pilot goes out during extremely cold winter nights. My thought is that the thermocoupler itself gets so cold those nights, the pilot cannot keep it warm enough to read that the pilot flame is on. > > Can it get so cold that a thermocoupler reads that the pilot is out even if it is on? Is it a sign of a bad thermocoupler or is there another fix I should look at. Check the piolet flame. It it hitting the thermocouple solid? How old is the thermocouple? It the connection to the main valve tight. Answer these questions first. Then change out the thermocouple and test the unit. ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [November 22, 2010, 2:00am UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/3 "2010-11-22T02:00:29Z")
A thermocouple should not stop working just because it’s a cold night. Replace it they’re not expensive. Your time is worth more than the part. ---
**Author:** ![raindog](https://avatars.discourse-cdn.com/v4/letter/r/2bfe46/32.png) [@raindog](https://boards.straightdope.com/u/raindog)\ **Post date:** [November 22, 2010, 2:01am UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/4 "2010-11-22T02:01:12Z")
As **Snnipe 70E** noted, the thermocouple needs “impingement”; it needs to be solidly in the flame. It’s unlikely, however, that it is somehow came loose and is no longer in the flame. High winds down the flue, or drafts will occasionally blow out the pilot flame. To answer your question it is impossible to have the pilot go out simply because it is cold outside. The more likely scenario is that you need a new thermocouple; a $10 part at Home Depot and a fairly straight forward DIY if you’re inclined to do it yourself. ---
**Author:** ![Kevbo](https://avatars.discourse-cdn.com/v4/letter/k/e47774/32.png) [@Kevbo](https://boards.straightdope.com/u/Kevbo)\ **Post date:** [November 22, 2010, 7:23pm UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/5 "2010-11-22T19:23:26Z")
A thermocouple actually has a little more output when the connection at the valve is colder…but a few degrees out of a thousand or so shouldn’t matter. This is a case where I would just replace the thermocouple. They are not expensive in the scheme of things, and do fail with the passage of time. AND I have heard even people who sell them call them thermocouplers. Nails on a chalkboard that is. ---
**Author:** ![Saint\_Cad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saint_cad/32/18907_2.png) [@Saint\_Cad](https://boards.straightdope.com/u/Saint_Cad)\ **Post date:** [November 23, 2010, 1:43am UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/6 "2010-11-23T01:43:51Z")
If it is a bad thermocouple then why would it only go out on cold nights and independent of the wind? ---
**Author:** ![Harmonious\_Discord](https://avatars.discourse-cdn.com/v4/letter/h/74df32/32.png) [@Harmonious\_Discord](https://boards.straightdope.com/u/Harmonious_Discord)\ **Post date:** [November 23, 2010, 3:15am UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/7 "2010-11-23T03:15:34Z")
A failing thermocouple acts like you described. You can’t depend on it. ---
**Author:** ![janeslogin](https://avatars.discourse-cdn.com/v4/letter/j/df788c/32.png) [@janeslogin](https://boards.straightdope.com/u/janeslogin)\ **Post date:** [November 23, 2010, 10:36pm UTC](https://boards.straightdope.com/t/do-i-have-a-bad-thermocoupler/561489/8 "2010-11-23T22:36:12Z")
We had a similar problem, old Whirlpool, spouse found a place online to ask questions and they chose to just sent us the whole works underneath, for free, FedX overnight. Don’t know why but you know the thing about a gift horse.