# Problem with my heater **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** heating, b4000, coolant, mazda\ **Created:** [November 24, 2010, 1:21am UTC](https://community.cartalk.com/t/problem-with-my-heater/57918 "2010-11-24T01:21:21Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![ctm533](https://avatars.discourse-cdn.com/v4/letter/c/3d9bf3/32.png) [@ctm533](https://community.cartalk.com/u/ctm533)\ **Post date:** [November 24, 2010, 1:21am UTC](https://community.cartalk.com/t/problem-with-my-heater/57918/1 "2010-11-24T01:21:21Z")
I’m having a problem with my truck’s heater. It puts out hot air when the temp is above (roughly) 20 degrees outside. When it gets very cold (right now, it’s -5), the heater blows only slightly warm air. This happened last winter, however, it was only really cold for about a week. When the temp hung around 20-25 at the coldest, I didn’t have any problems and forgot to fix it. Any help is appreciated. ---
**Author:** ![BustedKnuckles](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bustedknuckles/32/25_2.png) [@BustedKnuckles](https://community.cartalk.com/u/BustedKnuckles)\ **Post date:** [November 24, 2010, 1:29am UTC](https://community.cartalk.com/t/problem-with-my-heater/57918/2 "2010-11-24T01:29:47Z")
What year, how many miles? When was the last time the cooling system was checked? When was the last time the coolant was flushed and filled? With a new thermostat and radiator cap? The symptoms you describe are typical for a thermostat that is failed open. The coolant on cold days gets cooled too much from the radiator, and keeps the engine too cool as well. A new thermostat will fix this. Couple that with a coolant flush-n-fill and a new radiator cap should keep it fixed. ---
**Author:** ![ctm533](https://avatars.discourse-cdn.com/v4/letter/c/3d9bf3/32.png) [@ctm533](https://community.cartalk.com/u/ctm533)\ **Post date:** [November 24, 2010, 4:36am UTC](https://community.cartalk.com/t/problem-with-my-heater/57918/3 "2010-11-24T04:36:57Z")
1999 - 84K. I’ve had it since 2006. I’m not sure when the last time the cooling system was checked / last time the coolant was flushed. If was filled last winter. I think the thermostat is the original. I’ll replace the thermostat and flush/fill the coolant and see how it goes - thanks for the help. Also, my “check engine” light came on the other day. I took it to Autozone and they hooked it up to their handheld. It said that plugs 1,2 and 3 were misfiring (all 3 on the passenger side). I haven’t noticed any power issues / backfires / chugging, etc. Do you think this could be a serious issue? The plugs were replaced in June 2009. Thanks ---
**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\ **Post date:** [November 24, 2010, 12:19pm UTC](https://community.cartalk.com/t/problem-with-my-heater/57918/4 "2010-11-24T12:19:22Z")
``` [i] my "check engine" light came on the other day. I took it to Autozone and they hooked it up to their handheld. It said that plugs 1,2 and 3 were misfiring (all 3 on the passenger side).[/i] ``` I would consider new wires for the ignition. A set of OEM wires (not the fat colorful fancy ones for the hot rods) would be a good idea. Wires have a limited live and 100,000 miles range is certainly not a bad time to replace them. I don’t know the B4000 but some cars have some common parts for each side, that might be worth checking. For example if they each have a coil shared on that side, then that coil would be suspect. ---
**Author:** ![ken\_green](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/ken_green/32/816_2.png) [@ken\_green](https://community.cartalk.com/u/ken_green)\ **Post date:** [November 24, 2010, 11:26pm UTC](https://community.cartalk.com/t/problem-with-my-heater/57918/5 "2010-11-24T23:26:08Z")
The super cold may have an effect on the aging vacuum operated water valve you’ll find in the heater hoses near the firewall.