# Eclipse blows cold air at stop light **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [March 14, 2008, 10:29pm UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808 "2008-03-14T22:29:24Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![cwulbr](https://avatars.discourse-cdn.com/v4/letter/c/f6c823/32.png) [@cwulbr](https://community.cartalk.com/u/cwulbr)\ **Post date:** [March 14, 2008, 10:29pm UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/1 "2008-03-14T22:29:24Z")
I have a 2003 Mitsubishi Eclipse with 48,000 miles on it. During the winter when tooling along on the highway the heater blows comfortable warm air. However, when I stop at a stop light the heater blows cold air until I get underway again. And, NO, the AC is not on! ---
**Author:** ![homer2804](https://avatars.discourse-cdn.com/v4/letter/h/e9a140/32.png) [@homer2804](https://community.cartalk.com/u/homer2804)\ **Post date:** [March 14, 2008, 10:38pm UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/2 "2008-03-14T22:38:27Z")
Low coolant can cause this. When driving the water pump sends coolant faster and I guess at higher pressure than at idle. The others on here are more knowledgeable and I may be off target a little. ---
**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:** [March 14, 2008, 10:51pm UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/3 "2008-03-14T22:51:28Z")
I’d be inclined to suspect that the thermostat is stuck open and the engine is cooling down. It’s transferring a lot less heat to the coolant when it’s idling. ---
**Author:** ![meaneyedcatz](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/meaneyedcatz/32/692_2.png) [@meaneyedcatz](https://community.cartalk.com/u/meaneyedcatz)\ **Post date:** [March 15, 2008, 2:16am UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/4 "2008-03-15T02:16:46Z")
If your coolant is full there could be an air pocket somewhere that is causing this. Also check to see if Mitsu. has a TSB( technical service bulletin) ---
**Author:** ![Jad2007](https://avatars.discourse-cdn.com/v4/letter/j/dec6dc/32.png) [@Jad2007](https://community.cartalk.com/u/Jad2007)\ **Post date:** [March 15, 2008, 2:52am UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/5 "2008-03-15T02:52:52Z")
I have this same problem, except the heat isn’t that great when driving either…then goes almost cold at idle. Could this still be air in the system? Coolant level is good. One hose going into the heater core is very hot, the other just warm. Any ideas? ---
**Author:** ![cadillactech](https://avatars.discourse-cdn.com/v4/letter/c/a87d85/32.png) [@cadillactech](https://community.cartalk.com/u/cadillactech)\ **Post date:** [March 15, 2008, 3:03am UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/6 "2008-03-15T03:03:33Z")
If checking the coolant proves to be full - check heater hoses going into the heater core - if one if hot and one is warm or cold you have a blockage in the heater core - you can try to backflush the core with clean water but that may not work depending on how clogged it is but worth a try before replacing the heater core ---
**Author:** ![meaneyedcatz](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/meaneyedcatz/32/692_2.png) [@meaneyedcatz](https://community.cartalk.com/u/meaneyedcatz)\ **Post date:** [March 15, 2008, 4:40am UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/7 "2008-03-15T04:40:20Z")
I have never felt heater hoses while working but seems to me the heater core might have a block. Don’t take my word for it though. ---
**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:** [March 15, 2008, 11:08am UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/8 "2008-03-15T11:08:15Z")
Let me add one more thing. Does it also do it when you accelerate? If so it may be a vacuum problem. ---
**Author:** ![Jad2007](https://avatars.discourse-cdn.com/v4/letter/j/dec6dc/32.png) [@Jad2007](https://community.cartalk.com/u/Jad2007)\ **Post date:** [March 15, 2008, 3:05pm UTC](https://community.cartalk.com/t/eclipse-blows-cold-air-at-stop-light/11808/9 "2008-03-15T15:05:07Z")
That sounds like what my problem is…on a 99 STS, had the notorious head gaskets go, so I think someone might have used some sort of stop leak to fix it before they were replaced properly. Could it still be air in the system though?