# Diagnosing Heater issue. 2004 Accord **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** heating, honda, water-pumps\ **Created:** [February 14, 2019, 4:41pm UTC](https://community.cartalk.com/t/diagnosing-heater-issue-2004-accord/134615 "2019-02-14T16:41:01Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![Zarathuztra](https://avatars.discourse-cdn.com/v4/letter/z/46a35a/32.png) [@Zarathuztra](https://community.cartalk.com/u/Zarathuztra)\ **Post date:** [February 14, 2019, 4:41pm UTC](https://community.cartalk.com/t/diagnosing-heater-issue-2004-accord/134615/1 "2019-02-14T16:41:01Z")
2004 Honda Accord EX; 2.4L Recent work includes: Oil change, rack and pinion replaced, power steering pump replaced + belt, pads and rotors **Symptoms** Heater is blowing cool air, but not all the time. If in the driveway, 100% cool. If on the road it will be cool, until RPM goes up from either driving on the freeway, or when I tested using a low gear to get the RPM up. Basically, when the RPM is up the heater is functioning OK. Also, I observed that the thermostat gauge on the dash was showing the temp either normal or quite hot, approaching full hot (would sit around 90%). The timings would be such that the cool air is blowing and the dash reads hot on thermostat, I get the RPM going and after a few moments (~15 sec) the thermostat heads to a normal position and the heater is sending hot air as it should. _Do these symptoms make the cause apparent?_ _What steps or tests could I take to properly diagnose or narrow down the issue?_ **Initial Diagnosis from my searching** Water pump? Digging through information on faulty heaters pointed me to the coolant levels, I checked and coolant wasn’t super low, but could use more. I still have to get some during my lunch hour to top it off. I did have to replace coolant during the warmer months a few times this past year. I was expecting the loss to be coming from a crack in the coolant recovery tank, but now I am worried it may be from the water pump after watching some videos about heaters not working. Thanks ---
**Author:** ![tcmichnorth](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tcmichnorth/32/25126_2.png) [@tcmichnorth](https://community.cartalk.com/u/tcmichnorth)\ **Post date:** [February 14, 2019, 4:50pm UTC](https://community.cartalk.com/t/diagnosing-heater-issue-2004-accord/134615/2 "2019-02-14T16:50:49Z")
Never drive a vehicle when it is overheated. 90% is too hot. You do not have heat due to problems with your cooling system. This needs to be repaired immediately. If you have had to add coolant, there is a leak either internally or externally. When you get that repaired and coolant is filled and bleed, your heater will work, if you don’t damage engine by driving while too hot.